unit 1 Flashcards
(124 cards)
1
Q
what does a nucleotide contain
A
phosphate group
deoxyribose sugar
base
2
Q
what can be found at each prime end
A
5’ = phosphate
3’ = deoxyribose sugar
3
Q
what makes the sugar phosphate backbone?
A
phosphate group
deoxyribose sugar
4
Q
what bonds are base pairs held together by?
A
weak hydrogen bonds
5
Q
what bonds hold together the sugar phosphate backbone?
A
sugar-phosphate bonds
6
Q
the structure of DNA
A
nucleotides join together in an antiparallel structure to form a double stranded helix
7
Q
what prime end can new nucleotides be added to?
A
3’ end
8
Q
how can DNA be found?
A
linear chromosomes
circular chromosomes
9
Q
prokaryotes DNA
A
No nucleus
Circular chromosomes (storied in cytoplasm)
Circular plasmids (carry non-essential genes)
10
Q
eukaryotes DNA
A
Contains nucleus
Plant + animal cells
Linear chromosomes (storied in nucleus)
Mitochondria and chloroplasts = circular chromosomes
Yeast
Linear chromosomes (storied in nucleus)
Circular plasmids
11
Q
what is DNA in eukaryotes tightly packaged around?
A
proteins called histones
12
Q
stages of DNA replication
A
formation of the leading strand
formation of the lagging strand
13
Q
leading strand stages
A
DNA unwinds and weak hydrogen bonds break
Primer attaches to the 3’ end of the template DNA strand
The enzyme DNA polymerase attaches free DNA nucleotides to the primer at the 3’ end
DNA polymerase then catalyses the sugar-phosphate bond between the nucleotides
Replication is continuous
14
Q
lagging strand steps
A
Each fragment is primed
DNA polymerase binds nucleotides together in fragments from the primers 3’ end
Primer is then replaced by DNA
The enzyme ligase joins these fragments together
Replication is discontinuous
15
Q
replication of DNA requirements
A
template DNA
primers
a supply of nucleotides
DNA polymerase
ligase
ATP supply
16
Q
what is a primer?
A
attaches to the 3’ end of the template DNA
shows the start point of DNA replication
17
Q
what does DNA polymerase do?
A
Attaches free DNA nucleotides to the primer at the 3’ end
Catalyses the sugar-phosphate bond between the nucleotides
18
Q
what does ligase do?
A
Joins the fragments of DNA together in the lagging strand
19
Q
what is the importance of DNA replication?
A
ensure an exact copy of DNA is passed onto each daughter cell
20
Q
steps of PCR
A
DNA heated to break H bonds
cooled allowing primers to bind to target sequence
heated for heat-tolerant DNA polymerase to add nucleotides to the primers at the 3’ end of the original strand
21
Q
temperatures in PCR
A
95 (92-98)
55 (50-65)
75 (70-80)
22
Q
why does DNA polymerase have to be heat-tolerant in PCR?
A
ensures the enzyme does not denature
23
Q
where does PCR take place?
A
thermocycler
24
Q
requirements for PCR
A
DNA template strand
primers
supply of nucleotides
DNA polymerase
25
uses of PCR
paternity suits
help solve crime scenes
diagnose genetic disorders
26
genotype
determined by the sequence of bases in its genes
27
phenotype
determined by the proteins that are synthesised when genes are expressed
(physically look like)
28
mRNA
carries a copy of the genetic code from the nucleus to the ribosome
29
tRNA
each tRNA molecule carries its specific amino acid to the ribosome
30
rRNA
forms the ribosome with proteins
31
codon
each triplet on the mRNA molecule and codes for a specific amino acid
32
introns
non-coding regions of DNA
33
exons
coding regions of DNA `
34
where does transcription occur?
nucleus
35
how is mRNA formed?
RNA polymerase moves along gene unwinding the double helix - breaking H bonds
RNA polymerase synthesises a primary transcript from RNA nucleotides by complementary base pairing
36
how does RNA polymerase know when to form a mRNA primary transcript?
starts when it reads the start codon
ends with it reads the stop codon
37
how is the mature transcript formed?
splicing
introns are removed from the primary transcript and exons are spliced together to form the mature transcript
order of exons is unchanged
38
what occurs after splicing?
mature mRNA transcript leaves the nucleus into the cytoplasm at the ribosome
39
how can multiple genes be expressed from the one protein?
alternative splicing
different mature mRNA transcripts are produced depending on which exons are retained
40
where is tRNA found?
cytoplasm
41
structure of a tRNA molecule
one triplet of bases called an anticodon which is complementary to an mRNA codon
this is specific to an aimco acid which is found on the amino acid attachment site at the other end
42
where does translation occur?
ribosome
43
how does protein synthesis begin?
when the start codon is read
44
describe tRNA in translation
complementary tRNA anticodons attach to the mRNA strand bringing a specific amino acid
45
how is a protein formed in translation?
the amino acids which are brought by tRNA are bonded together by peptide bonds
tRNA then leaves once they are attached
this forms a polypeptide
46
how does protein synthesis stopped?
when the stop codon is reached
47
describe the structure of a polypeptide
folds to form a 3D shape of a protein
held together by hydrogen bonds and other interactions
48
what forms the ribosome?
proteins
rRNA
49
what is differentiation?
the process by which a cell expresses certain genes to produce a characteristic for the cell type
50
what do stem cells have the ability to do
differentiate to carry out specialised functions
self-renew
51
embryonic stem cells differentiation abilities
Differentiate into all the cell types that make up the organism = pluripotent
All the genes in embryonic stem cells can be switched on
52
where are embryonic stem cells found?
from the early stages of an embryo
53
tissue stem cells differentiation abilities
They can differentiate into all cell types found in a particular tissue type = multipotent
Many genes are already switched off
54
example of tissue stem cell
blood stem cells in bone marrow can give rise to all types of blood cell
55
where are tissue stem cells found?
tissues throughout the body
56
what are tissue stem cells involved in?
growth, renewal, repair
57
therapeutic use of stem cells
involved in the repair of diseased or damaged organs
corneal repair
skin grafts
58
research use of stem cells
provides information on cell processes = cell growth, differentiation and gene regulation
how diseases develop
drug testing
59
ethical issues of embryonic stem cells
Can lead to effective treatments for disease and injury
Involves the destruction of the embryo
Reduces animal testing
60
what is an organisms genome?
its entire hereditary information encoded in its DNA
61
what is the genome made of?
DNA sequences that code for a protein (genes)
Non-coding DNA sequences
62
function of coding sequences in the genome?
Code for amino acid sequences in proteins
63
function of non-coding sequences in the genome?
regulate transcription by turning genes on/off
transcribed but not translated
64
example of non-coding sequences transcribed but not translated
tRNA
rRNA
65
what is a mutation?
changes in DNA that can result in no protein or an altered protein being synthesised
66
how can mutations occur?
spontaneous
random
rarely
67
how are mutations the driving factor of evolution?
normally have negative effects but occasionally mutation may be advantageous, increases variation
68
single gene mutations
substitution
insertion
deletion
69
substitution mutations
missense
nonsense
splice-site
70
missense mutation
one amino acid changed for another
produces a non-functional protein
71
nonsense mutation
premature stop codon produced
shorter protein
72
splice-site mutation
some introns being retained and/or some exons not being included in the mature transcript
73
type of insertion/deletion mutation
frameshift mutation
74
frameshift mutation
All of the codons and all of the amino acids after the mutation are changed
Major effect on the structure of the protein and it is almost certain to be non-functional
75
types of chromosome mutations
deletion
duplication
inversion
translocation
76
deletion chromosome mutation
A section of a chromosome is removed when it breaks in two places and a segment in between becomes detached
Chromosome is short and lacks certain genes
77
duplication mutation
A section of a chromosome is added from its homologous partner
78
inversion mutation
The chromosome breaks in two places and the segment in between is reversed
79
translocation mutation
One section of a chromosome breaks off and attaches to another chromosome that is not its homologous partner
80
importance of duplication mutation
allows potential beneficial mutation to occur in duplicated gene whilst original gene still expresses its own protein
produces a second copy that is free from selection pressures
81
what is evolution?
changes in organisms over generations as a result of genomic variation
82
natural selection
non-random increase in the frequency of DNA sequences that increase survival and the non-random reduction in the frequency of deleterious sequences
83
types of natural selection
stabilising
directional
disruptive
84
stabilizing selection
An average phenotype is selected for and extremes of the phenotype are selected against
This means there is a smaller range of values so less variation in the population
85
directional natural selection
One extreme of the phenotype range is selected for as it gives a selective advantage
86
disruptive natural selection
Two or more phenotypes are selected for (not the average)
The population is split into two or more distinct groups with different characteristics
87
types of gene transfer
vertical
horizontal
88
vertical gene transfer
Occurs in eukaryotes and prokaryotes and involved genes being passed from parents to offspring
89
how does vertical transfer occur?
through sexual or aesexual reproduction
90
horizontal gene transfer
Prokaryotes can transfer genes between individuals of the same generation
91
why do prokaryotes have faster evolutionary change?
they use vertical and horizontal transfer
92
what is speciation?
generation of a new biological species by evolution
93
types of speciation
allopatric
sympatric
94
difference between allopatric and sympatric?
allopatric = gene flow is prevented by a geographical barrier
Sympatric = gene flow is prevented by an ecological or behavioural barrier
95
speciation steps
population occupies the same environment
isolation barrier splits into sub-population
different mutations occur
natural selection occurs
barrier removed and they can no longer interbreed to product fertile offspring
96
what does an isolation barrier do?
prevent gene flow between sub-populations
97
isolation barriers
geographical
behavioural
ecological
98
what is genomics?
the study of genomes
99
what is genomic sequencing?
the sequence of nucleotide bases can be determined for individual genes are entire genomes
100
what genomes have been sequenced?
Disease-causing organisms
Pest species
Species that are important model organisms for research
101
reasons for genomic sequencing
accurate diagnosis
specific pest control
model organisms
102
accurate diagnosis for genomic sequencing
Disease causing organisms have been sequenced to help with accurate diagnoses
103
specific pest control for genomic sequencing
Pest species have been sequenced to develop more specific measures of control rather than using general pesticides
104
model organisms for genomic sequencing
Model organisms (fruit flies) have been sequenced so they can be used in medical research in place of mammals, reducing ethical concerns and cost
105
what is required for comparative genomics?
bioinformatics
106
what are bioinformatics?
computer and statistical analysis
107
what are special about computer programs?
can be used to identify base sequences by looking at sequences similar to known genes
108
what has comparative genomics revealed?
genes are highly conserved
109
what can highly conserved DNA be used for?
comparing the genomes of two species
- the greater number of conserved genes, the closer they are related
110
what is phylogenetics?
the study of evolutionary history and relationships
111
what is used to construct a phylogenetic tree?
comparative genomics
112
what are requirements for the main sequence of events in evolution?
DNA sequence data
fossil records
113
lineage
a sequence of species which have evolved from ancestry populations
114
a sequence divergence
Describes when lineages diverged from a common ancestor
115
main sequence of events on life list
Cells
Last universal ancestor
Prokaryotes
Photosynthetic organisms
Eukaryotes
Multicellularity
Animals
Vertebrates
Land plants
116
molecular clocks
used to estimate when species diverged
117
what is required for molecular clocks?
DNA sequence data
fossil records
mutation rate
118
what is a molecular clocks disadvantage?
assumes a constant mutation rate
119
how can you work out how long ago species diverged?
the number of nucleotide differences as nucleotide substitutions is regarded as being proportional to time
120
what is personalised medicine?
individuals personal genome can be used to select the most effective drugs and dosage to treat their disease
121
pros of personalised medicine
It can be used to predict a future disease diagnosis
There could be early intervention to take preventative measures
The ideal prescription and dosage of medication can be given
122
cons of personalised medicine
Who should be allowed to access this information?
Could employers, life insurers or offspring be allowed to demand this information?
123
what is pharmacogenetics?
the study of the genetic variation between individuals that affects their response to drugs/pharmaceuticals
124
how can the cause of inherited diseases be found?
by comparing the DNA of affected and unaffected individuals to reveal the precise mutation which caused the mutation
