Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

biology > manipulating genomes > Flashcards

manipulating genomes Flashcards

1
Q

what does a PCR allow scientists to do

A

produce a lot of DNA from tiniest original sample
(amplify the DNA)
from 1 million to 10 billion copies

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

requirements for PCR

A

DNA sample
excess triphosphate of the 4 bases
enzyme DNA polymerase
PCR machine (thermal cycler)
primers
Mg2+ cofactor for DNA polymerase

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

what are the excess triphosphate of the 4 bases called in PCR

A

dNTP’s (deoxynucleotide triphosphate)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

what DNA polymerase enzyme is used in PCR & why

A

Tap polymerase (from thermophilic bacterium = Archaea)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

what does Mg2+ cofactor allow for in PCR

A

enables tight binding between active site and substrate

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

what are primers and what are they used for in PCR

A

short sequences of bases
site of attachment for Taq polymerase to bind

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

stages of PCR

A
  1. denaturation of double stranded DNA
  2. annealing of primers
  3. elongation/synthesis of DNA
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

denaturation of double stranded DNA (step 1 of PCR) description

A

H bonds are broken between the 2 strands to form 2 separate strands (normally carried out in the body by helicase enzyme)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

what temperature is denaturation of double stranded DNA (step 1 of PCR) carried out at

A

90-95C

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

annealing of primers (step 2 of PCR) description

A

primers bind to 3’ end of DNA
needed for DNA/Taq polymerase to attach and start replication
primers bind by H bonds

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

what temperature is annealing of primers (step 2 of PCR) carried out at

A

55-68C

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

elongation/synthesis of DNA (step 3 of PCR) description

A

Taq polymerase moves from 5’ to 3’ direction, forming phosphodiester bonds between nucleotides
complementary strand of DNA formed

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

what temperature is elongation (step 3 of PCR) carried out, why at and for how long

A

71-75C (optimum temperature for Taq polymerase)
for at least 1 minute

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

how many copies of DNA sample does 30 cycles of PCR give

A

about 1 billion

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

in PCR, how is size of DNA sample said to grow

A

exponentially (it is logarithmic)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

how many fragments of DNA after 5 PCR cycles

A

2^5= 32
log32= 1.51
10^1.51 fragments

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

what is electrophoresis (general)

A

a technique used in laboratories in order to separate macromolecules (DNA or proteins) based on size

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

how accurate is electrophoresis

A

accurate enough to separate nucleic acid fragments that are different buy only 1 base in length

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

what is agarose

A

carbohydrate mesh compatible w DNA/protein in electrophoresis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

what does electrophoresis use as medium

A

a gel ‘plate’ or ‘slab’ containing agarose which is covered in a buffer solution

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

purpose of buffer solution in electrophoresis

A

allows electrical current to travel across whole tank

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

what is attached at each end of gel in electrophoresis and why

A

electrodes
so a current can be passed through it

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

step by step basic procedure to separate DNA fragments in electrophoresis

A
  1. dna samples treated w restriction enzymes to cut large fragments to smaller fragments
  2. dna samples placed in wells cut in negative electrode (cathode) end of gel
  3. gel immersed in tank of buffer solution and an elec current passed through solution for fixed time period (usually 2 hr)
  4. DNA is -vely charged, so attracted to +ve electrode (so DNA fragments diffuse through gel towards +ve electrode end (anode))
  5. shorter lengths of DNA move faster and so move further in fixed time that current is passed through gel
  6. position of fragments can be shown using dyes that stain DNA molecules OR southern blotting can be used w radioactive probes if a particular sequence is being searched for
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

what is negative electrode called

A

cathode

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

what is positive electrode called

A

anode

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

why is DNA negatively charged

A

because of the many phosphoryl (phosphate) groups (-ve sugar phosphate backbone)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

how can position of fragments be shown after electrophoresis

A

use dyes that stain DAN molecules
us Southern blotting and radioactive probes (if a particular sequence is being searched for)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

why do different proteins move less/more far through gel in electrophoresis

A

proteins have different R groups so different 3D shapes (tertiary structures) and overall charges which would affect movement through gel

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

method used to cancel out charges of protein R groups

A

SDS PAGE

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

how does SDS page work?

A

when a protein mixture is heated in presence of SDS, the protein is denatured (reverts to its primary structure) and so charges and hydrophobic regions are exposed
the SDS detergent wraps around the polypeptide backbone so that the intrinsic charges of polypeptides become negligible when compares to the -ve charges contributed by SDS

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
31
Q

SDS binds to proteins in proportion to what
what does this result in

A

their RMM
a molecule with a uniform mass:charge ratio
this means they can be separated on the basis of their size

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
32
Q

results of SDS PAGE to proteins

A

all proteins now linear (straight chains of amino acids)
all molecules negatively charged so all move in same direction in gel (attracted to anode)
small molecule move through gel faster (bc lower RMM)
standards of known mass run in adjacent lanes for comparison (control/baseline)
proteins obtained from gel for identification

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
33
Q

uses of SDS PAGE

A

analysis of haemoglobin for diagnosis of sickle cell anaemia (missense mutation w 1 amino acid change)
urine protein electrophoresis (proteins w/ an MR >69000 are able to pass into BC)
analysis of plasma proteins for diagnosis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
34
Q

how much DNA is used when an individuals DNA is profiled

A

short sections of non-coding DNA (satellite DNA, does not code for proteins)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
35
Q

what does a human genome contain

A

simple repetitive sequences that are scattered throughout our 46 chromosomes which are called Tandem repeats

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
36
Q

what are variable number tandem repeats

A

tandem repeats which are highly variable in length

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
37
Q

why is every person’s DNA is unique

A

due to the variable length of their tandem repeats
this can be used to identify them

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
38
Q

where do tandem repeats occur

A

at more than 1000 locations in the genome

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
39
Q

what is a DNA probe

A

short sequence of DNA that binds complementary to certain sequences

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
40
Q

stages involved in DNA profiling

A

extraction
digestion
separation (gel electrophoresis)
separation (southern blotting)
hybridisation
development

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
41
Q

describe stage 1 extraction in dna profiling

A

dna extracted from sample semen, blood, skin cells, hair roots, saliva
PCR used to amplify DNA

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
42
Q

describe stage 2 digestion of DNA profiling

A

strands of DNA are cut into small fragments using restriction endonuclease
different enzymes cut DNA at specific nucleotide sequences
all restriction enzymes make 2 cuts: one through each strand of DNA (cuts leave VNTRs intact)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
43
Q

describe stage 3 Gel electrophoresis of DNA profiling

A

cut fragments separated on basis of charged particles moving through an agarose gel under the influence of an electric current
-ve charged PO4^3- groups cause DNA to move to anode
smaller fragments move further
gel immersed in alkali to separate DNA double helix into single strands

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
44
Q

describe stage 4 southern blotting of DNA profiling

A

single stranded DNA transferred to nylon membrane which is placed over gel
membrane covered w several sheets of dry absorbent paper drawing alkaline solution containing DNA through membranes
DNA unable to pass through membrane and is transferred to same relative position on membrane as in gel
DNA is fixed

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
45
Q

describe stage 5 hybridisation of DNA profiling

A

radioactive or fluorescent probes are added in excess to DNA fragments
DNA probes are short DNA or RNA sequences complementary to known DNA sequence and it binds to it
probes identify VNTRs

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
46
Q

describe stage 6 development of DNA profiling

A

radioactive probes-> x ray image taken -> autoradiograph
fluorescent probes -> UV light and they glow
fragments give a pattern of bars called a DNA profile
unique profile for each person except identical twins
technique is v sensitive and even a trace of DNA left when someone touched an object can produce results

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
47
Q

uses of DNA profiling

A

forensic science
maternity and paternity cases
species identification
identifying individuals at risk of developing particular diseases

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
48
Q

uses of DNA profiling: forensic science

A

criminal convictions:
DNA traces obtained from blood, semen, saliva, hair roots and skin cells. DNA profile compared to sample taken from suspect/criminal database
identification:
victims body parts after air crashes etc
match profiles from descendants of those lost in WW1 w unidentified remains of soldiers

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
49
Q

uses of DNA profiling: maternity and paternity cases

A

half genetic material from mum and half from dad
all bars from child’s profile not matched in 1 parent must be matched in other parent’s profile

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
50
Q

uses of DNA profiling: species identificaiton

A

used to demonstrate evolutionary relationship between different species

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
51
Q

uses of DNA profiling: identifying individuals at risk of developing particular diseases

A

certain non-coding VNTRs have been found to be associated with an increased risk of a particular disease eg various cancers and heart diseases

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
52
Q

2 examples of DNA sequencing

A

Sanger sequencing
pyrosequencing

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
53
Q

define the term DNA sequencing

A

finding the order/sequence of bases/nucleotides in DNA

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
54
Q

step by step Sanger sequencing

A

DNA chopped into fragments and each fragment is sequenced 5’ to 3’ (similar to DNA rep)
DNA for sequencing is mixed w a primer, DNA polymerase and an excess of normal free activated nucleotide and terminator bases
mixture placed in thermal cycler that rapidly changes temp in programmed intervals in a repeated cycle (96C, 50C, 60C)
each time a terminator base is incorporated instead of normal nucleotide, synthesis of DNA stops. (these r present in lower amounts and are added at random, resulting in many DNA fragments of diff lengths)
after many cycles, all possible length DNA chains will be produced
DNA chains separated according to length by capillary sequencing (works like gel electrophoresis in minute capillary tubes and shortest lengths travel fastest)
fluorescent markers on terminator bases used to identify final base of each fragment- lasers detect diff coloured tags and thus order of bases in sequence (of new complementary strand- use to build up sequence in OG DNA strand)
data fed into computer that reassembles genome by comparing all fragments and finding areas of overlap between them

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
55
Q

what are terminator bases (used in Sanger sequencing)

A

modified version of the 4 nucleotides
called ddNTPs (dideoxynucleotide triphosphate)
have H instead of OH on C3
inhibit DNA polymerase
stop DNA synthesis when they are included

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
56
Q

what are terminator bases given in Sanger sequencing

A

different coloured fluorescent tags or radioactive labels

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
57
Q

what is a primer (used in Sanger sequencing)

A

short sequence of DNA that binds complementary to the DNA sample (allows DNA polymerase to attach)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
58
Q

Sanger sequencing DNA polymerase

A

must be thermostable eg. Taq
must withstand 96C

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
59
Q

describe what happened at each temp in Sanger sequencing

A

96C: double strand of DNA separates to single strands (denaturation)
50C: primer anneals (binds to) DNA strand
60C: DNA polymerase starts to build up new DNA strand by adding nucleotides w complementary bases to ss template DNA

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
60
Q

what is pyrosequencing also known as

A

high throughput sequencing

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
61
Q

2 uses of DNA sequencing

A

bioinformatics
computational biology

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
62
Q

what is bioinformatics w/ example use

A

creating online databases that solve global issues
it allows rapid access to large volumes of data which is universally available
format is the same across all countries
could be used to identify a source of disease outbreak, target most vulnerable individuals and start appropriate treatment

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
63
Q

what is computational biology

A

making comparisons between DNA sequences, which allows comparison of newly discovered sequences and previously discovered sequences

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
64
Q

why are bioinformatics and computational biology useful:

A

facilitate access to large amounts of data
format of information s inuversal
computational biology allows rapid comparison of stored sequences and new sequences eg. can analyse 3000 genes in 100 samples in minutes
genes can be put into clusters which show the same pattern of green expression
can perform statistical analyses

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
65
Q

describe genome-wide comparisons between individuals: 2 types

A

human genome project
analysing genomes of pathogens

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
66
Q

how many genes/base pairs does the human genome contain

A

24000 genes
3 billion base pairs

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
67
Q

what is genomics

A

changing epidemiology (study of distribution and determinants of disease)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
68
Q

what do computerised comparisons between genomes of people with/without a disease allow for

A

detection of particular mutations that could be responsible for an increased risk of disease

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
69
Q

example of using human genome project in epidemiology

A

mutations of BRCA1 gene linked to breast cancer

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
70
Q

what are places where substitutions occur called
effects?

A

single nucleotide polymorphisms or SNPs
silent (no effect on protein), missense/nonsense (alter protein or way RNA regulates expression of another gene in some way)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
71
Q

what is methylation

A

adding a methyl group to certain chemical groups (cytosine and adenine) in DNA
plays a major role in regulating gene expression in eukaryotic cells

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
72
Q

what does acetylation do

A

increase gene transcription

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
73
Q

what does methylation in gene promoter region of DNA do

A

represses gene transcription (DNA wraps more tightly around histones)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
74
Q

what is epigenetics

A

control of gene expression by modification of DNA (switching genes on/off)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
75
Q

what can methods to map the methylation of whole human genomes help w

A

helps researchers understand the development of certain diseases
e.g. certain types of cancer & why they may not develop in genetically similar individuals

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
76
Q

what does sequencing genomes of pathogens (fast and cheap) allow doctors to do?

A

find source of an infection eg MRSA
identify antibiotic resistant strains ensuring antibiotics only used when they will be effective (allows selection of a narrow-spectrum antibiotic), which is useful for bacteria that are slow to culture
monitor potenital epidemics e.g. covid 19
many pathogens eg viruses have a high mutation rate and so many strains exist (variants- antigens changing shape)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
77
Q

sequencing DNA allows doctors to identify them and then implement specific treatment plans: give examples

A

identify targets in the development of drugs
identify genetic markers coding for proteins which act as antigens which can be used in vaccines (allow recognition by immune system)
test to identify who is infected so they can self isolate to decrease transmission. tests look for pathogen antigen in body e.g. lateral flow tests for covid 19

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
78
Q

how does bioinformatics allow for species identification

A

there are particular sections of the genome that are common to all species but vary between them, so comparisons can be made
scientists can determine which species an organism belongs to by comparison to a standard sequence for different species

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
79
Q

species identification in animals

A

uses cytochrome c oxidase (evidence for evolution- look at amino acid sequence)
short section so can be sequenced quickly and cheaply, yet varies enough to give clear differences between species
fewer differences= more recent common ancestor

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
80
Q

species identification in plants

A

cytochrome c oxidase region of DNA does not evolve quickly enough to show differences between species
2 region of DNA in chloroplasts are used

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
81
Q

is species identification by bioinformatics available for fungi/bacteria yet

A

no suitable regions of DNA suitable yet

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
82
Q

bioinformatics to find evolutionary relationships (phylogeny)

A

DNA sequences of diff organisms can be compared bc basic mutation rate of DNA can be calculated
scientists can work out how long ago 2 species diverged from a common ancestor

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
83
Q

how do spliceosomes join same exons

A

single gene may produce several different versions of functional mRNA
coding for different sequences of amino acids- primary structure
resulting in different proteins
resulting in different phenotypes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
84
Q

what is synthetic biology

A

using GMOs to produce drugs/medicines/useful molecules
OR
synthesis of new genes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
85
Q

what is personalised medicine

A

the choice/development of a drug is linked to the genotype of the individual

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
86
Q

examples of synthetic biology

A

information storage
production of medicines
novel protein
genetic engineering
use of biological system in industrial contexts
synthesis of new genes or replacement of faulty ones
synthesis of biosensors
food production
production of monoclonal antibodies for targeted drug deliveries

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
87
Q

describe information storage (type of synthetic biology)

A

can encode vast amounts of digital info onto single strands of synthetic DNA

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
88
Q

example: production of medicines (type of synthetic biology)

A

GM E.coli to make human insulin

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
89
Q

describe genetic engineering (type of synthetic biology)

A

e.g. similar to Hb can bind to oxygen but not carbon monoxide

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
90
Q

describe use of biological system in industrial contexts (type of synthetic biology)

A

‘cells’ (chemical cells) to hydrolyse cellulose -> sugars which can be used as liquid fuel

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
91
Q

exampleof synthesis of new genes or replacement of faulty ones (type of synthetic biology)

A

eg treating cystic fibrosis (gene therapy)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
92
Q

example of synthesis of biosensors (type of synthetic biology)

A

eg GM bacteria that glow if air is polluted with eg petroleum pollutants

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
93
Q

describe food production(type of synthetic biology)

A

decrease fertiliser use by engineering synthetic microbial communities

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
94
Q

suggest how the interdisciplinary field of bioinformatics may be useful in determining whether a newly-sequence allele causes a genetic disease

A

base sequences of normal allele &known alternatives are held in database & amino acid sequences of known proteins
info held in universal format
computational analysis allows a rapid comparison between new sequences & previously known sequences

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
95
Q

describe differences between DNA profiling and DNA sequencing

A

DNA profiling produces a fingerprint unique pattern (from specific section of DNA), sequencing doesnt
sequencing determines order of DNA bases, profiling doesnt

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
96
Q

explain why only selected sections of non-coding DNA are used when profiling a human

A

in most people, genomes are very similar
so using coding sequences would not provide unique profiles
non-coding DNA contains short tandem repeats/variable number tandem repeats which vary between individuals

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
97
Q

suggest why the binding of SDS to proteins is necessary for protein electrophoresis

A

standardise mass:charge ratio so fragments are separated out based on size/mass
SDS makes all protein negative so they can be separated like DNA (from -ve to +ve terminals)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
98
Q

what is a DNA probe

A

a short single-stranded piece of DNA (50-80 nucleotides long) that is complementary to a section of DNA being investigated

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
99
Q

what is a DNA probe labelled by

A

using a radioactive marker (detected by exposure to x-ray)
using a fluorescent marker (emit colour when exposed to UV light)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
100
Q

what do DNA probes bind to

A

any fragment where a complementary base sequences is present
binding by complementary base pairing is called annealing (H bonds form)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
101
Q

uses of DNA probes

A

locates specific gene for genetic engineering
identify same gene in a variety of genomes e.g. separate species to show phylogeny
identify presence or absence of allele for a particular genetic disease (could inform genetic counselling)
used in electrophoresis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
102
Q

what do scientists use DNA microarrays for

A

to measure the expression levels of large numbers of genes simultaneously and reveal the presence of mutated alleles (expression level determined by presence of mRNA)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
103
Q

what does each DNA spot on a microarray contain

A

a specific DNA sequences (probe)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
104
Q

how does a microarray work

A

mature mRNA extracted from cells eg tumour and normal cell
mRNA converted to ss cDNA using reverse transcriptase
amplified using PCR
cDNA labelled with fluorescent markers
applied to DNA chip where it anneals to cDNA probes
reference (normal) and test (tumour) DNA samples are labelled w different fluorescent markers
where a test subject or reference marker binds to a particular probe the scan reveals the fluorescence of one colour, indicating the presence of a particular sequence in the DNA
where both bind with a particular probe the fluoresces of both colours is seen

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
105
Q

MICROARRAY (red=tumour sample, green=normal sample):
what does red mean

A

gene highly expressed in tumour cell but not normal cell

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
106
Q

MICROARRAY (red=tumour sample, green=normal sample):
what does green mean

A

gene highly expressed in normal cell but not in tumour cell

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
107
Q

MICROARRAY (red=tumour sample, green=normal sample):
what does yellow mean

A

gene highly expressed in both tumour and normal cell

108
Q

microarray: how is ratio of expression in tumour: normal cells calculated

A

the colour/intensity of the dots are converted to numbers and the ration is calculated

109
Q

MICROARRAY:
what does a ratio greater than 1 mean

A

gene expression induced by tumour formation
this info can be used to target drugs to tumour cells

110
Q

MICROARRAY:
what does a ratio less than 1 mean

A

gene expression repressed by tumour formation

111
Q

MICROARRAY:
what does a ratio equal to 1 mean

A

tumour has no effect on gene expression

112
Q

what is recombinant DNA

A

combing DNA from 2 different species (transgenic organism formed)

113
Q

stages involved in genetic engineering

A

isolating desired gene
putting gene into vector
transferring vector into host cell
host cell expresses new gene

114
Q

3 types of isolating desired gene in genetic engineering

A

directly from DNA
from mRNA
from the nucleotide sequence of the gene

115
Q

step 1 of genetic engineering: isolating desired gene: directly from DNA

A

a DNA probe can be used to locate the gene within the genome and the gene can be cut out using a restriction endonuclease
these enzymes can be used to cut DNA at a specific sequence along the length of the DNA
some make a clean, blunt cut but many cut the 2 DNA strands unevenly leaving 1 strand longer than the other

116
Q

what are regions of unpaired bases called

A

sticky ends

117
Q

what do sticky ends allow for

A

tighter annealing between vector DNA and gene of interest (H bonds form as well as phosphodiester bonds)

118
Q

step 1 of genetic engineering: isolating desired gene: from mRNA

A

mRNA is isolated for the desired gene from cells expressing the gene
e.g. pancreas cell for insulin gene
using the mRNA as a template, an enzyme called reverse transcriptase is used to make a singe strand of cDNA
primers are added and DNA polymerase can make this cDNA into a double stranded length (must be same as double-stranded plasmids)

119
Q

why is isolating desired gene from mRNA rather than DNA advantageous

A

because introns have already been spliced out (post-transcriptional modification)
many copies of mRNA available
mRNA is only from gene coding for insulin (being expressed)

120
Q

step 1 of genetic engineering: isolating desired gene: from the nucleotide sequence of the gene

A

if scientists know the nucleotide sequence of the gene, then the gene can be synthesised using an automated polynucleotide synthesiser (synthetic biology)

121
Q

3 methods of putting gene into a vector in genetic engineering

A

using plasmids
using viruses
using liposomes

122
Q

step 2 of genetic engineering: putting gene into a vector: using plasmids

A

plasmids are cut using the same restriction enzyme as was used to cut out the gene, so cut plasmid has complementary sticky ends
ligase enzyme catalyses the condensation reactions that form phosphodiester bonds between sugar and phosphate groups on 2 strands of DNA. H bonds form between complementary bases
this forms recombinant DNA

123
Q

what is recombinant DNA

A

molecule created in vitro by joining foreign DNA with vector molecule e.g. plasmid and human gene

124
Q

what type of genes do plasmids often have 2 of

A

marker genes

125
Q

what are plasmid marker genes for and how can scientists use them

A

may have a gene for antibiotic resistance
scientists ca determine which genes have taken up the plasmid by growing on media containing antibiotics
however some plasmids will be modified but others won’t be
the 2nd marker gene gets cut when gene is inserted so no longer functions (used to determine which cells have taken up modified plasmid)

126
Q

step 2 of genetic engineering: putting gene into a vector: using viruses

A

genes can be put into attenuated viruses (made harmless) that then carry gene into host cells

127
Q

step 2 of genetic engineering: putting gene into a vector: using liposomes

A

liposomes consist of plasmid DNA surrounded by a lipid bilayer so it can fuse w the cell membrane of various cell types
liposomes can have monoclonal antibodies attached to their surface which means they target particular cell types (immunotherapy)
e.g. supplying genes to cancer cells to activate tumour suppressor genes

128
Q

5 methods of transferring vector into host cell in genetic engineering

A

heat shock treatment
electroporation
electrofusion
transfection
using bacteria: Agrobacterium tumefaciens

129
Q

step 3 of genetic engineering: transferring vector into host cell: heat shock treatment

A

bacteria subjected to alternation periods of 0C and 42C in presence of calcium chloride so walls and membranes become more permeable and allow DNA in
+ve calcium ions surround -vely charged parts of both DNA molecules and phospholipids in plasma membranes reducing repulsion between the 2
increases no. & size of pores which decreases need for channel/carrier proteins

130
Q

step 3 of genetic engineering: transferring vector into host cell: electroporation

A

high voltage pulse applied to cell to disrupt membrane by inducing pores to form (by introducing recombinant DNA at same time as the electric field, the DNA is likely to be taken up)
used to get DNA plasmids into bacteria or DNA fragments into eukaryotic cells

131
Q

step 3 of genetic engineering: transferring vector into host cell: electrofusion

A

tiny electric currents applied to membrane of 2 different cells
this fuses the cells and nuclear membranes of the 2 different cells together to forma. hybrid/ polyploid cell containing DNA from both
in plants, cell walls are removed using cellulase, followed by electrofusion, followed by use of hormones to stimulate growth of new cell wall
used to produce GM plants
used in somatic cell nuclear transfer

132
Q

is electrofusion successful in animalss

A

no but it is important in the production of monoclonal antibodies
a monoclonal antibody is produced by a combination of a cell producing 1 single type of antibody w a tumour cell, which means it divides rapidly in culture

133
Q

step 3 of genetic engineering: transferring vector into host cell: transfection

A

DNA can be packaged into a bacteriophage- virus that infects bacterial cells and transfers DNA into host bacterial cell

134
Q

step 3 of genetic engineering: transferring vector into host cell: using bacterium Agrobacterium tumefaciens

A

plasmids are inserted into the bacterium which infects some plants and naturally inserts its genome into host cell genomes
(can introduce insecticide-resistant genes/ herbicide-resistant genes)

135
Q

step 4 of genetic engineering: direct transfer of gene into recipient

A

small pieces of gold or tungsten are coated with the DNA and shot into plant cells = gene gun

136
Q

differences between TLC and electrophoresis

A

TLC: separates by relative solubility, E: separates by relative size/length
TLC: separates uncharged particles, E: separates charged particles
TLC: buffer not used, E: buffer used
TLC: no dyes used, E: dyes used (fluorescence/ radioactive)

137
Q

suggest why genome is fragmented before sequencing

A

genome is too large
fewer errors/greater accuracy

138
Q

why is Taq polymerase used for PCR

A

it is thermostable i.e. does not denature at 95C during strand separation
PCR can cycle repeatedly without having to replace the enzyme

139
Q

possible desired characteristics for plant GM

A

high yield
drought resistance
pesticide production

140
Q

step by step genetic engineering in plats using agrobacterium tumefaciens/ particle gun

A

1a. desired gene is placed in Ti plasmid of bacteria along with a marker gene e.g. antibiotic resistance or fluorescence. desired gene carried directly into plant cell DNA as bacteria infects cell
1b. alternatively a gene gun is used to get the genes into plant cell
2. transgenic plant cells form a callus (mass of GM cells)
3. each cell in callus can be grown into a new transgenic plant using plant hormones to encourage root and shoot formation

141
Q

what is gene therapy

A

inserting functional allele of a particular gene into a cell that contains mutant and non-functioning allele of that gene
if inserted allele is expressed, functioning protein will be produced

142
Q

types of gene therapy

A

somatic gene therapy
germ line gene therapy

143
Q

describe somatic gene therapy

A

only affects body cells (alteration to patients genome but these changed not inherited)
involves inserting functional allele into body cells
only temp. solution & when somatic cell dies, somatic cell replaced w stem cells that will have faulty allele (needs repetitive treatment)
faulty allele passed onto offspring
can only be used to treat recessive genetic disorders
dominant condition faulty protein produced and you can’t stop this and can’t remove dominant allele

144
Q

describe germ line gene therapy

A

involves inserting cantonal alleles into gametes/zygotes
all cells of individual are altered (inherited by future generations and does not need to be repeated; is permanent)
has the potential to change genetic make-up of many people, the descendants original patient; none of whom could give consent)
concerns that genes may find their way into a location that could disrupt the expression & regulation of other genes (increased risk of cancer)
technology might eventually be used to enable people to choose desirable or cosmetic characteristics of their offspring
considered ethically impermissible for humans
successfully done on animal embryos

145
Q

somatic vs gene line therapy permanence?

A

somatic= temporary, needs repetitive treatment
germ line= permanent, doesnt need to be repeated

146
Q

how does germ line therapy increase the risk of cancer OR epigenetic changes

A

concerns that genes may find their way into a location that could disrupt the expression and regulation of other genes
gene could insert itself into a regulatory region

147
Q

is gene transfer predictable
what does this depend on

A

no; unpredictable
depends on where the allele inserts

148
Q

example of somatic gene therapy

A

cystic fibrosis

149
Q

what is cystic fibrosis caused by

A

inheritance of 2 recessive alleles

150
Q

describe cystic fibrosis

A

production of lots of very thick mucus as a result of a defective chloride ion channel
outward flow fo Cl- prevented which results in Na+ entering cell to balance charge
prevent water leaving cells resulting in thick mucus

151
Q

how does somatic gene therapy treat cystic fibrosis

A

functional alleles (to synthesise functional protein= CFTR channel) can be packaged into virus/ liposomes which can then be inhaled (inhaler/nebuliser)
the functional alleles will get into some of the cells lining the respiratory tract and the host cell will produce functional CFTR protein (functional allele must pass through
nuclear membrane & integrate into chromosomes)
epithelial cells replace every 10-14 days so treatment must be repeated at regular intervals

152
Q

problems with using a virus to insert gene (IN VIVO)

A

virus may still evoke an immune response
patient may become immune to virus so subsequent deliveries impossible
virus may insert allele in location that disrupts gene regulating cell division, increasing risk of cancer
virus may insert allele in location that disrupt regulation of gene expression of other gene

153
Q

describe ex vivo somatic gene therapy

A

adult stem cells isolated from patient and propagated in lab and therapeutic gene introduced into cells
GM cells reintroduced into patient
produce cells w functional proteins

154
Q

what does genetic manipulation refer to

A

changing structure of DNA in an organism

155
Q

ethical issue with genetic manipulation

A

problem or situation that requires person/organisation to choose between alternatives that must be evaluated as right (ethical) or wrong (unethical)

156
Q

general positive issues of genetic manipulation

A

benefit to human health (could improve symptoms of diseases)
decrease starvation, make life-saving drugs, patenting generates funds for research, technology transfer to LIDCs: improved QoL
reduced use of pesticide (decreased chance of bioaccumulation)

157
Q

general negative issues of genetic manipulation

A

risk to human health (could cause frameshift mutations)
animal welfare; not right to treat animals poorly
GM animals reduced to commodities
patenting increases cost
GM crops encourage monoculture (increased susceptibility to disease, climate change etc.) and decrease biodiversity (decrease species diversity)
using organisms as models for disease deliberately causes them harm

158
Q

examples of GM plants

A

insect resistant GM soya
herbicide resistant soya
nutritionally enhances GM rice: golden rice

159
Q

positive ethical impacts of using insect resistant GM soya

A

increases yield, cheaper product
reduces starvation
reduced use of chemical pesticides
benefit to human health

160
Q

negative ethical impacts of using insect resistant GM soya

A

pest may become resistant to toxin
engineered plant would be ineffective , pest number would increase and eat other crops
increases starvation
plant may produce toxins which are toxic to humans
risk to human health
Bt is toxic to some non-pest species, reducing biodiversity (reduced species diversity)

161
Q

describe insect resistant GM soya

A

soya= good source of protein, vitamins and minerals
Bt toxin coded for= poisnonous to insect pest
binds to receptors of epithelial cells in larva gut, causing formation of pores/ion channels so WP imbalance, killing insect

162
Q

describe herbicide resistant soya

A

modified plant expresses a gene from agrobacterium tumefaciens
allows plant to make essential amino acids even after herbicide spray

163
Q

positive ethical impacts of herbicide resistant soya

A

use of herbicide kills competing weeds (decreased interspecific competition)
therefore increases yield
reduces starvation

164
Q

negative ethical impacts of herbicide resistant soya

A

may encourage monoculture, decreasing biodiversity
encourages natural selection of super weeds (directional selection)
herbicide risk to human health bc carcinogenic
leaches into waterways, leading to eutrophication

165
Q

describe golden rice

A

2 genes (1 from daffodils, 1 from soil bacteria) inserted into rice genome to activate production of beta carotene, a precursor for vitamin A which is needed to produce visual pigment rhodopsin (improves vision, particularly at night)

166
Q

positive ethical impacts of golden rice

A

reduces blindness in potentially over 500,000 annually in India

167
Q

negative ethical impacts of golden rice

A

potential costs issues for seeds but free humanitarian use licences offered to farmers so they can keep and replant seeds -> stunt to gain public acceptance of use of GM crops
reduce in biodiversity
safety of engineered rice?
risk to human health
GM rice could breed with wild type and contaminate these populations

168
Q

describe pharming

A

GM animals to produce a human protein for use as a medicine

169
Q

examples of pharming

A

gene inserted into fertilised sheep’s egg, along w a promotor sequence (specific location for RNA polymerase to bind to) so that the gene is expressed only in the mammary gland so protein can be harvested from the milk
transgenic sheep with human gene that coded for AAT (decreases emphysema): protein too large for production in bacterial cell
goats w gene for spider milk
creating animal models so they develop certain diseases e.g. mice

170
Q

positive ethical impacts of pharming
(sheep milk protein production, goat spider silk, animal model diseases)

A

used to treat hereditary deficiency of AAT which leads to emphysema
benefit to human health
silk from goats used for sutures, artificial ligaments
animal models allow diseases to be studies and drugs tested
benefit to human health

171
Q

negative ethical impacts of pharming
(sheep milk protein production, goat spider silk, animal model diseases)

A

inserting foreign alleles into another organism may cause them harm (ie could disrupt regulatory genes)
possible that trans gene would be activated in places other than mammary gland and resulting protein may be toxic to animal
inflicting unnecessary suffering on an animal (but they are valuable so very well looked after)

172
Q

GM humans in gene therapy positive ethical impacts

A

benefit to human health
e.g. potential treatment of cystic fibrosis

173
Q

negative ethical impacts of GM humans in gene therapy

A

potential problems of using viruses as vectors:
may insert allele in location that disrupts gene involved in regulating cell division, leading to cancer or disrupting expression of other genes
human germ line therapy is ethically impermissible (many generations of offspring cannot have given consent)

174
Q

describe/examples GM pathogens for research

A

GM viruses with no virulence can be used to make vaccines
some tumour cells have receptors on membranes for poliovirus so poliovirus will recognise and attack them
poliovirus GM to inactivate genes that cause polio

175
Q

positive ethical impacts of GM pathogens for research
(viruses w no virulence for vaccines, poliovirus gene inactivation)

A

reduces chance of vaccine making recipient ill and vaccines saves lives
possible treatment for some forms of brain cancer and saves human lives

176
Q

negative ethical impacts of GM pathogens for research
(viruses w no virulence for vaccines, poliovirus gene inactivation)

A

researchers become infected with live pathogen (unlikely as more harmless viruses chosen), but potential mass outbreak of disease
GM virus reverts back to original form, leading to disease outbreak
use in biowarfare

177
Q

positive ethical impacts of GM pathogens

A

GM bacteria makes human insulin: benefit to diabetics (T1 autoimmune)
GM viruses can also act as vectors in gene therapy

178
Q

negative ethical impacts of GM pathogens

A

bacteria have antibiotic resistance genes and could transfer these to other bacteria by exchanging plasmids (modified so can’t grow outside lab)
allele may be inserted into genome in a way that increases risk of cancers or may interfere w gene regulation: risk to human health

179
Q

describe patenting

A

legal protection for GM techniques or products
by law can control who uses product and how for a set period of time

180
Q

positive ethical impacts of patenting

A

owner of patent gets money from product: used in further research, generates competition between companies carrying out GM, get GM products faster
patent allows public to hold owner of patent accoutnable

181
Q

negative ethical impacts of patenting

A

patented products not affordable in 3rd world, so starvation increases
treats life as a commodity; patent undermines dignity by allowing ‘ownership’ of genes

182
Q

positive ethical impact of technology transfer (sharing of GM knowledge, skills and tech)

A

globally GM products can be created at a faster rate

183
Q

negative ethical impact of technology transfer (sharing of GM knowledge, skills and tech)

A

may be cost implications if patents involved which may limit who uses GM product

184
Q

differences between somatic gene therapy and germ line gene therapy

A

S: insertion of functional allele into body cells, GL: insertion of functional allele into gamete/zygote
S: temporary, short term solution which needs repetitive treatment, GL: permanent long term solution, no further treatment required
S: cannot be inherited, GL: can be inherited
S: only some cells get allele, GL all cells get allele

185
Q

“GM plants and animals should be classed as new species””
evidence for/against

A

use fertility as a basis
breed GM organisms with non-GM and observe whether they are fertile
is so, same species
or compare DNA band patterns by electrophoresis

186
Q

explain why primers are needed for PCR but not for natural DNA replication

A

DNA polymerase cannot bind to ssDNA

187
Q

which parts of the genome are compares in DNA profiling for forensics

A

non-coding regions (introns, STRs, VNTRs, minisatellites, micro satellites)

188
Q

in gel electrophoresis, what are DNA markers

A

mixtures of DNA molecules of known size
run in 1 lane & used to estimate sizes of other DNA samples

189
Q

explain how genome sequencing an help identify evolutionary relationships

A

closer % match of genome sequence means less time since the 2 species diverged from a common ancestor

190
Q

what is epidemiology

A

study of incidence, distribution and possible control of disease (& other factors relating to health)

191
Q

what is a restriction enzyme

A

enzyme that cuts a dsDNA fragment at a specific place (its recognition site)

192
Q

what is meant when a restriction enzyme site is said to be ‘palindromic’

A

has same sequence on both strands (reading from 5’ to 3’)

193
Q

what process could be used to describe the reverse of restriction digestion?

A

DNA ligation

194
Q

name common vectors used in genetic engineering

A

cosmids
viruses
BACs
liposomes

195
Q

what is the role of DNA ligase

A

joins DNA backbone/sugar phosphate backbone
makes phosphodiester bonds

196
Q

how are restriction enzymes used in genetic modification

A

cut plasmid,
isolate gene
producing sticky ends

197
Q

negative aspect of GM-ing plants

A

expensive to buy so farmers may be priced out
chance of gene transfer to create superweeds
create monocultures (susceptibel to extinction)

198
Q

why is it harder to treat genetic disorders caused by dominant alleles than disorders caused by recessive alleles

A

recessive allele treatment needs addition of ‘correct’ allele anywhere in genome
treatment of dom. allele disorder requires that specific gene to be disrupted/silenced -> more specific placement of inserted DNA

199
Q

similarities between DNA sequencing and DNA replication

A

both sequence 5’ to 3’
both use DNA polymerase
both require dNTPs

200
Q

similarities between PCR and DNA replication

A

both copy DNA
both use DNA polymerase
both sequence 5’ to 3’
both form phosphodiester bonds between nucleotides
both require dNTPs
H bonds break between complementary strands in both

201
Q

differences between DNA sequencing and DNA replication

A

S: involves electrophoresis to separate strands in mass order, R: no electrophoresis
S: whole new complementary fragment sequenced, R: each new DNA mol consists 1 original strand and 1 new strand (semi conservative)
S: sequencing of unknown fragments, R: replication of known sequences
S: requires addition of synthetic primers, R: no primers
S: requires thermal cycling, R: none
S: H bonds break due to high temps 96C, R: H bonds break due to helicase
S: no gyrase or ligase, R: uses gyrase and ligase
S: terminator bases (ddNTPs) involved, R: none

202
Q

differences between PCR and DNA replication

A

P: exponential growth, R: linear growth
P: DNA polymerase has optimum temp 64 to 62C : Taq, R: optimum temp 37C
P: only short sequences can be rep, R: entire chromosome replicated
P: more copies of DNA forms, R: 1
P: requires addition of synthetic primers, R: none
P: H bonds broken by high temps, R: H bonds broken by helicase
P:thermal cycling, R: body temp
P: no gyrase or ligase, R: both
P: Mg ion cofactor, R: none

203
Q

what is a clone w a couple examples

A

genetically identical organisms produced by asexual reproduction (mitosis)
e.g. yeast budding, bacteria by binary fission

204
Q

advantages of cloning

A

if conditions favour the parents they will also favour the offspring
rapid process so can rapidly colonise new environment
only 1 parent needed

205
Q

disadvantages of cloning

A

overcrowding so leads to intraspecific competition
limited genetic diversity (except mutations)
natural selection does not occur
environmental changes e.g. new disease or drastic climate change may wipe out a population if all are vulnerable

206
Q

how are plant clones formed

A

by vegetative propagation (asexual reproduction in which new plants develop from meristematic regions (undifferentiated cells in vegetative organs of plant (stem, roots and leaves)) rather than specialised reproductive structures)

207
Q

types of vegetative propagation

A

runners
rhizomes
tubers
suckers
bulbs
corms
leaves/plantlets
layering

208
Q

what are runners
example
use in horticulture

A

horizontal stems on surface of ground that can form roots at certain points
strawberries
removing young plants from runners

209
Q

what are rhizomes
example
use in horticulture

A

stout horizontal stems underground that can form roots at certain points
ginger
cutting up rhizomes

210
Q

what are tubers
examples
use in horticulture

A

swollen end of underground stem/root
potatoes=stem, dahlias=root
removing tubers and planting separately

211
Q

what are suckers
example
use in horticulture

A

new stems that grow from roots of plants
banana trees
dig out suckers and plant separately

212
Q

what are corms
example
use in horticulture

A

underground solid stem w scaly or fleshy leaves
crocus
dividing up corms, remove baby corms, known as cormels or cormlets, attached to the bottom

213
Q

what are leaves/plantlets
example
use in horticulture

A

immature plants grow on leaf margins, drop off and take root
Bryophyllum spider plants
remove immature plants and plant separately

214
Q

what is layering
example
use in horticulture

A

portion of an aerial stem grows roots while still attached to the parent plant and then detaches as an independent plant
honeysuckle peg stem below ground to encourage root formation

215
Q

describe how to take a cutting (4 marks)

A

cut a healthy shoot between 2 nodes at an angle
dip in rooting powder
plant in deep compost
remove lower leaves and cover with a transparent plastic bag

216
Q

why would you remove a shoot for a stem cutting in the early morning

A

contains most water bc stomata not open overnigth

217
Q

why a clean diagonal cut when taking a cutting

A

increased surface area for root growth and uptake of water and minerals

218
Q

why remove lower leaves when taking a cutting

A

most energy can be channelled into root growth and less water loss by transpiration

219
Q

why remove flowers and buds when taking a cutting

A

stop energy usage for flowers but increased energy for root growth

220
Q

what does rooting powder contain when taking plant cutting

A

synthetic auxin
cytokinins
to increase root growth

221
Q

why should compost for plant cutting be well watered and not too compressed

A

air spaces for O2
provides water for p/s

222
Q

why cover plant with transparent plastic bag or cut off lemonade bottle when doing plant cutting

A

light can reach it
increases humidity to decrease water loss

223
Q

why keep plant cutting warm but avoid direct sunlight

A

allows low levels of p/s
warm for enzymes
avoid damage to chloroplasrs

224
Q

why mist leaves of plant cutting regularly

A

maintains high humidity

225
Q

what is grafting

A

joining 2 plant stems together to produce hybrid variety w combined characteristics

226
Q

grafting use

A

select for particular colour
select for disease resistance, pesticide production, heat tolerance

227
Q

what is tissue culture

A

series of techniques used to grow cells or tissues or organs from a small sample of cells or tissue
carried out on a (agar) nutrient medium under sterile conditions
application of plant growth substances at the correct time can encourage the cells in growing tissue to differentiate

228
Q

what is micropropagation

A

making large numbers of genetically identical offspring from a single parent plant

229
Q

step by step micropropagation

A

suitable piece of plant taken and cut into small pieces (explant) e.g. leaf
meristematic tissue often used as this is usually free from virus infection e.g. apical bud
explants sterilised using dilute bleach/alcohol
explants placed in sterile growth medium. aseptic techniques used. sterile agar gel contains suitable nutrients e.g. amino acids, sucrose and a high conc of growth substances e.g. auxin, cytokinins to stim. mitosis for root/shoot growth
once a callus forms, split into many smaller calluses
clumps stimulated to grow, divide and differentiate into plant tissues by moving cells onto diff growth media (changing ratio at different times/stages of growth e.g. more auxins for root growth, less for shoot growth)
tiny platelets transferred to greenhouse to be grown in compost or damp soil and acclimatised to normal growing conditions (LI, temp, CO2 conc)

230
Q

why are explants sterilised in micropropagation

A

kills any bacteria/fungi which would otherwise thrive in these conditions

231
Q

examples of aseptic techniques used in micropropagation

A

wash hands
disinfect bench
windows closed
bunsen flame to create convection current

232
Q

what is a callus

A

mass of undifferentiated totipotent (can differentiate into any cell type) identical cells

233
Q

arguments in favour of micropropagation

A

allows rapid production of large number of plants w known genetic makeup and therefore display desirable characteristics
generally produces disease-free plants
can produce viable number of plants after GM or selective breeding
way of producing a large number of plants which are seedless (sterile) eg bananas and grapes
way of growing plants which are naturally relatively infertile or difficult to grow from seeds eg orchids
way of reliably increasing the no. of rare/ endangered plats
new plants are uniform in phenotype which makes them easier to grow and harvest
facilities can be set up anywhere in the world at any time so not dependent on climate

234
Q

arguments against micropropagation

A

produces a monoculture so all plants may be susceptible to same disease/ change in env.
if source material is infected by a virus, all clones will be infected (explants and platelets are vulnerable to infection by moulds)
large numbers of plants can be lost during the process
loss of variation and genetic diversity
labour intensive: relatively expensive to maintain sterile conditions and requires skilled workers

235
Q

why are plants more able to form natural reproductive clones than animals

A

have meristematic tissue and almost all stem cells are totipotent
plant specialised cells can undifferentiated and then re-differentiate
animals only have multipoint stem cells and tissue specific stem cells

236
Q

cloning in invertebrate animals name and brief description

A

parthenogenesis
in greenflies and water fleas
female produces a diploid egg without fertilisation

237
Q

describe parthenogenesis in aphids

A

summer growing season: female aphids produce diploid eggs by mitosis (genetically identical to each other and parent)
these eggs develop inside the body of the female, hatch and emerge as miniature adults (not fertilised by sperm to form zygotes)
some species produce winged females in summer months (probably triggered by low food quality or poor conditions for colony)
in autumn a change in photoperiod and temp (or lower food quality/quantity) causes females to produce females and males by parthenogenesis. sexual female and males mate, and females lay eggs that dev outisde of mother. eggs endure winter and emerge as winged or wingless females in following spring (genetic variation as a result of meiosis and random fertilisation)

238
Q

examples of natural clones in animal species

A

parthenogenesis
fragmentaiton in flatworms
budding in hydra
natural identical (monozygotic) twins in mammals

239
Q

describe fragmentation in flatworms

A

flatworm stretches itself to breaking point and each part forms a complete flatworm

240
Q

describe budding in hydra

A

small ‘buds’ produced on side of adult body
form tentacles and separate from adult

241
Q

describe natural identical (monozygotic) twins in mammals

A

fertilised egg (zygotę) or early embryo splits in 2
both the embryos that are formed implant in uterus and develop
3 per 1000 natural pregnancies in humans
rare in domestic cattle

242
Q

what does artificial embryo splitting/twinning/cloning produce

A

2 or more individuals that are clones of each other but not of either parent

243
Q

describe artificial embryo splitting/twinning/cloning in cow example

A

cows w desirable traits treated w hormones to super ovulate
treat female w hormones to ensure correct stage of menstrual cycle
ova may be fertilised naturally or by artificial insemination by a bull w good traits
early embryos fused out of uterus
around day 6 when cells of embryo are still totipotent (can still become cells of placenta/umbilical cord). embryos are split to produce several smaller embryos
each embryo grown in lab for few days and a single one implanted into each surrogate mother (female cows have single pregnancies)-> in pigs a number of cloned embryos are put into a surrogate mother (multiple piglets)
number of genetically identical cows born from different mothers (exact phenotype unknown until birth so no guarantee)
embryos may be frozen and transported around the world

244
Q

what is super ovulating

A

producing many eggs

245
Q

describe reproductive cloning by enucleation and somatic cell nuclear transfer (SCNT) using sheep as example

A

somatic cell taken from udder of female transgenic sheep and extract nucleus using micropipette
take an egg cells from a female of the same species and enucleate it
use electrofusion/electroporation/heat shock treatment to fuse somatic nucleus into empty egg cell:triggers cell division by mitosis
split embryo into many smaller embryos and implant each into a surrogate mother

246
Q

requirement of surrogate organism for SCNT

A

must be of same species
most be of good health, free from disease, treated w hormones so at correct stage of menstrual cycle

247
Q

offspring of SCNT DNA

A

mitochondrial DNA identical to that of egg donor (from enucleated egg cell)
nuclear DNA identical to that of nucleus donor

248
Q

what is non-reproductive/ therapeutic cloning?

A

follows same initial stages as reproductive cloning but once embryo has formed the cells are removed and subdivided
these stem cells can grow into any type of cell

249
Q

induced pluripotent stem cells formation and use in medicine

A

patients cells taken e.g. skin and treated w reprogramming factors and pluripotent stem cells formed that are genetically identical to patient so will not be rejected

250
Q

SCNT: longevity of animals?

A

dolly wasp put down when’s he was 6 years old bc she suffered form arthritis and lung disease
techniques have been improved ad mice now cloned that have normal life expectancies

251
Q

use of animal cloning in agriculture

A

producing many individuals that have same productive features
e.g. high milk yield

252
Q

uses of animal cloning in medicine: subcategories?

A
  1. pharming
  2. transplants
  3. scientific research
253
Q

uses of animal cloning in medicine: pharming

A

producing lots of genetically identical sheep that have been genetically engineered to produce human proteins
e.g. human factor VIII (blood clotting factor)
goats w spider silk genes (can produce silk in their milk, used for suturing)

254
Q

uses of animal cloning in medicine: transplants

A

producing GM pigs which grow organs that have the potenital to be used in human transplants
pigs used, HOWEVER their organs are coated in carbohydrate molecule that triggers reaction reaction in humans (autoimmune response) SO pigs are GM using gene editing technologies e.g. make antigens less harmful to reduce risk of rejection

255
Q

why are pigs used for transplants

A

pigs used bc anatomically similar to humans, large litters, reproduce rapidly

256
Q

uses of animal cloning in medicine: scientific research

A

share findings with other scientists on the effects of medicinal drugs

257
Q

argument for using embryo splitting as a type of animal cloning

A

produce max. number of offspring (many more than normal reproduction) from particularly good animals

258
Q

argument against using embryo splitting as a type of animal cloning

A

not possible to predict exactly how productive animals produced by embryo cloning will be as not genetically identical to either parent (phenotype unknown)

259
Q

arguments for using SCNT as type of animal cloning

A

produces genetically identical copies of v high value individuals (cloning successful racehorses)
allows specific animals to be cloned eg replacing specific pet
potenital to allow rare endangered or extinct animals to be reproduced (simlar to plants)

260
Q

arguments against using SCNT as type of animal cloning

A

very inefficient (Dolly took 277 cell fusions): many cloned animals fail to develop and miscarry/ produce malformed offspring
many SCNT cloned animals have short lifespans

261
Q

factors contributing to extra cost of micropropagation compared to traditional methods

A

maintaining sterile conditions is expensive
requires skilled workers/specialised training
labour intensive
high setup costs

262
Q

how is supply of cow egg cells obtained for cloning

A

egges flushed out of oviduct

263
Q

ways of setting up gene bank for animal

A

sperm banks
egg banks
embryo freezing
zoos/wildlife reserves

264
Q

how can cloning help save an endangered species of mammal

A

increase rate of reproduction so population size rapidly increased
doesn’t require a fertile female bc uses surrogate
embryo can be subdivided (embryo splitting)
van use adult cells from all existing members of species to maximise genetic diversity

265
Q

differences between Sanger sequencing and high throughput sequencing

A

high throughput sequences more DNA/bases per unit time
high throughput can sequence longer DNA sequences
Sanger uses terminator bases
Sanger=1 enzyme
Sanger involves electrophoresis

266
Q
A

biology (28 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions