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Biology > The control of gene expression 8 > Flashcards

The control of gene expression 8 Flashcards

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1
Q

what is a mutation

A

an abnormal change in the DNA base sequence

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2
Q

what are the potential impacts of a mutation

A

different amino acids are coded for, so a different base sequence is present, meaning a different protein structure when the polypeptide chain assembles
highlight it says potential, as the genetic code is degenerate.

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3
Q

what are the main types of gene mutations

A

point mutations and frame shifts

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4
Q

what are point mutations

A

a mutation that just affects one nucleotide/base

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5
Q

what is a chromosome mutation

A

changes in the structure or number of whole chromosomes

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6
Q

what are the two types of chromosome mutations

A

changes in whole sets of chromosomes
changes in individual chromosomes

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7
Q

A mutation can lead to the production of a non-functional enzyme. Explain how (6)

A

Change in base sequence of DNA
So a change in the primary structure/amino acid sequence of the enzyme
SO theres a change in hydrogen/ionic /disulfide bonds
So theres a change in the tertiary structure
Theres changes in the active site of the enzyme, meaning it is no longer complementry to its substrate, and no E-S complexes form

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8
Q

What does totipotent mean

A

when a cell has the potential to become any cell

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9
Q

What are stem cells

A

undifferentiated dividing cells

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10
Q

What are some sources of stem cells in mammals

A

inner cell mass of a blastocyst
fetal stem cells
bone marrow

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11
Q

what does pluripotent mean

A

cells that can become almost any kind of cell

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12
Q

what does multipotent mean

A

cells can differentiate into a limited number of specialised cells

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13
Q

what does unipotent mean

A

cells that can only differentiate into a single cell type

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14
Q

what is an induced pluripotent stem cell

A

a type of pluripotent cell that is developed from a unipotent cell

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15
Q

Recall the levels of protein structure

A

Primary structure - a specific sequence of amino acids joined together by peptide bonds to form a polypeptide chain
Secondary structure - hydrogen bonds form between different amino acids, forming either a beta pleated sheet or an alpha helix
Tertiary structure - Disulfide bridges, ionic bonds, hydrogen bonds and hydrophobic/hydrophilic interactions form between R groups of amino acids, pulling the structure together
Quaternary structure - two or more polypeptide chains join together through hydrogen bonds

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16
Q

Translation steps

A

Translation
mRNA leaves nucleus through a nuclear pore
mRNA arrives at ribosome and binds to it at the start codon
tRNA molecules brings a specific amino acid to the ribosome
The anticodon on the tRNA is complementary to the codon on the mRNA
Peptide bonds will form between adjacent amino acids
Two tRNA molecules can enter the ribosome at a time
Multiple peptide bonds between multiple amino acids lead to the formation of a polypeptide chain

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17
Q

Transcription steps

A

Transcription
DNA helicase unwinds and unzips the DNA double helix into two strands by breaking the hydrogen bonds between complementary organic base pairs, and only one called the coding strand is used
Free, activated RNA nucleotides form temporary hydrogen bonds to complementary base pairs (uracil to adenine, cytosine to guanine)
RNA polymerase catalyses phosphodiester bonds between RNA nucleotides that are adjacent to each other, forming a mRNA molecule
mRNA detaches from the coding strand, and the DNA double helix rewinds itself

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18
Q

what is the difference between cell specialisation and cell differentiation

A

specialisation is the cell being changed to only able to carry out specific functions, where are differentiation is the process of the cell changing

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19
Q

Is cell specialisation reversible or irreversible

A

irreversible

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20
Q

Explain how oestrogen affects gene transcription

A

Oestrogen is lipid soluble and so cross the cell membrane via simple diffusion
Oestrogen binds to receptor on transcription factor, changing the tertiary structure
This allows the polymerase enzyme to attach to the beginning of the DNA double helix strands (promoter region)
ADD MORE

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21
Q

Outline the effect of oestrogen on transcription factors

A

Oestrogen is non-polar and therefore lipid soluble. It diffuses simply across the phospholipid bilayer.
Oestrogen binds to the receptor on the transcription factor, causing it to change in tertiary structure
Due to this change in tertiary structure, the transcription factor is now complementary to the promoter region of the target gene.
The transcription factor then binds to the promoter region at the start of the gene, activating RNA polymerase to start transcribing the gene.

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22
Q

if DNA is more tightly wrapped around the histone proteins, is the gene turned on or off. Why?

A

Off
Transcription factors cannot access the gene

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23
Q

if DNA is less tightly wrapped around the histone proteins, is the gene turned on or off. Why?

A

On
Transcription factors can access the gene

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24
Q

what is acetylation

A

the addition of an acetyl group to histone proteins from coenzyme A

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25
what is deacetylation
the removal of an acetyl group off of a histone by coenzyme A
26
what is methylation
the addition of a methyl group
27
how does methylation work (theres two ways)
attracts proteins that cause deacetylation of histones blocks promoter regions, preveenting transcription factors
28
acetylation results in a gene being...
expressed
29
methylation results in a gene being
not expressed
30
what is epigenetics
heritable changes in gene function, without changes to the base sequence of DNA.
31
describe the structure of a nucleosome
DNA wrapped around histone proteins, either tightly or loosely
32
what are the two genes involved in mutations that lead to cancer
the proto oncogene and the tumor suppressor gene
33
what are the two types of tumor
benign and malignant
34
features of benign tumors
dont spread through the body as they don't undergo metastasis metastasis is the breaking off of the tumour and spread by the blood stream all the cells are undifferentiated
35
features of malignant tumors
36
how can mutations of the DNA base sequence lead to a non-functional enzyme
change in the DNA base sequence there's a change in the amino acid sequence so a different tertiary structure due to different positions of hydrogen/ionic/disulphide bonds so a change in the shape of the active site so substrate can no longer for E-S complexes
37
whats a way to remember what methylation and acetylation do for epigenetics
InT: IM DNA/DAH INhibit Transcription by Increased Methylation of the DNA or Decreased Acetylation of associated Histones
38
what is a tumour
a mass of cells created by uncontrolled cell division
39
what is metastasis
cells breaking off of a tumour and travelling elsewhere in the body via the blood stream
40
which tumours, benign or malignant, undergo metastasis
malignant
41
What is the protooncogene and what does it do
a normal genen that codes for a protein that stimulates cell division
42
what makes a protooncogene become an oncogene, and what does this mean
a mutation will cause the proto oncogene to become an oncogene the mutation will change the amino acid sequence of the protein it codes for this creation results in the protein speeding up cell division too much, leading to a tumour growing
43
what is the tumour supressing gene and what does it do
a gene that has the normal function of coding for a protein that slows down the rate of cell division
44
what makes a tumour suppressor gene become unworking, and what does this mean
a mutation in the gene, meaning the protein that it codes for may not be able to slow down the rate of cell division this increases the risk of uncontrolled cell division and a tumour growing
45
The amount of methylation of tumour suppressor genes and oncogenes has an impact on cancer risk and implications for the design of cancer treatments. Discuss how this might occur.
Increased methylation of an oncogene will inhibit transcription of this gene. This could prevent uncontrolled cell division and tumour formation. Increased acetylation of a normal tumour suppressor gene will inhibit transcription of this gene. This could lead to uncontrolled cell division and tumour formation.
46
Describe how alterations to tumour suppressor genes can lead to the development of tumours (3)
increased methylation of tumour suppressor genes or a mutation in the tumour suppressor gene means that the gene is not transcribed and the amino acid sequence is altered so the protein doesnt work so uncontrolled cell division occurs
47
A type of malignant cell divides every 8 hours. Starting with one of these cells, how many tumour cells will be present after 4 weeks? Assume none of these cells will die. Give your answers in standard form
1.93 x 10^25 672 hours 672/8 = 84 divisions 2^84 = 1.93 x 10^25
48
what does RNAi do
translation of the mRNA produced by target genes can be inhibited
49
how does RNAi work
the double stranded RNA is broken up by an enzyme into small interfering RNA (siRNA) via hydrolysis One of the strands on siRNA combines with the enzyme the siRNA strand on the enzyme pairs with complementary bases of a mRNA strand the enzyme cuts the mRNA that the siRNA has binded to into smaller sections so the mRNA strand is destroyed
50
what changes can occur during transcription to mRNA
mutations epigenetic changes -> is the gene accessible are transcription factors activated -> e.g. by oestrogen
51
what changes can occur during translation to mRNA
siRNA (small interferring RNA)
52
what does hypermethylation mean
adding more methyl groups, turning the gene off
53
what does hypomethylation mean
removing methyl groups, turning the gene on
54
what is a genome
all the DNA in a cell organism
55
what is the sequencing of a genome
sequencing a genome involves working out the entire DNA base sequence for a cell organism
56
what is a cellular proteome
all the proteins producing by the genome in a given cell type
57
what is a complete proteome
all the proteins produced by the genome in the whole organism
58
what is a proteome
all the proteins produced by the genome
59
what is the importance of recombinant DNA technology
a lot of human diseases are caused by an individual lacking/being unable to produce a particular themselves e.g. insulin
60
what does it mean if a gene is in VIVO
the gene is transferred into a host cell using a vector to be cloned
61
recombinant DNA technology meaning
taking DNA from two sources and combining them
62
what are the steps to IN VIVO cloning (a gene in VIVO)
1 - isolation -> isolating the gene of interest 2 - insertion -> inserting gene OI into a vector 3 - transformation -> the plasmid transforms the bacterium 4 & 5 - identification and growth/cloning
63
we can call a bacterium that uptook the plasmid that has the new DNA in it
transformed and transgenic
64
what is a way of isolating a desired gene
using restriction endonucleases to cut out the fragment of DNA containing the desired gene of interest from the DNA
65
what does it means if a gene is in VITRO
the gene is copied using a method called PCR and is performed in a lab
66
what do we call a bacteria that has taken up the plasmid but shows no sign of containing the desired gene
transformed, and NOT transgenic
67
what are the 3 ways to isolate a gene
using reverse transcriptase using restriction endonucleases using a gene machine to create the gene
68
outline how we isolate a gene using reverse transcriptase
desired gene on the mRNA strand acts as a template as single stranded complementary copies of DNA (cDNA) is formed using reverse transcriptase cDNA is isolated by the hydrolysis of the mRNA strand DNA polymerase then combines complementary DNA nucleotides to the cDNA to form a double stranded DNA molecule that contains the code for the gene
69
outline how we isolate a gene using restriction endonucleases
specific endonuclease cuts into a specific point on the DNA strand plasmid is removed form bacterium same endonuclease that was used to cut the DNA fragment cuts the plasmid open the ends of the DNA and the gene are joined together by DNA ligase via phosphodiester bonds, sometimes this is called annealing
70
why is it that each restriction endonuclease will cut DNA at a specific base sequence
has a specific tertiary structure, so a specific active site that is complementary to the shape of a specific DNA base sequence
71
describe how restriction endonuclease and DNA ligase are used to insert a gene into a plasmid
restriction endonuclease cuts plasmid ligase joins gene/DNA and plasmid together
72
outline how we isolate a gene using a gene machine
a protein is used and worked ut backwards to the mRNA code to the DNA code machine starts by using free nucleotides to make lots of short, single stranded DNA molecules called oligonucleotides
73
what are marker genes and what do they do
genes that are used to detect cells or organisms that have been successfully genetically modified
74
outline the PCR cycle
heat to 95°C, as this will break the hydrogen bonds between DNA strands so that the strands separate reduce temperature to 55°C, as this will allows DNA primers to hydrogen bond with their specific complementary DNA bases on the DNA strands heat back up to 72°C, as this will allow DNA nucleotides to be added to each primer via complementary base pairing with the template strand, joined together by DNA polymerase
75
what are the 'ingredients' for a PCR tube
DNA sample, DNA polymerase, free DNA nucleotides, DNA primers
76
how can we increase the permeability of a cell membrane
heat it, or increase concentration of Ca2+ ions
77
what is a DNA probe
short, single stranded DNA molecule that has bases complementary with a target DNA base sequence
78
what is the general method to using DNA probes
DNA sample is extracted and amplified using PCR and then broken down into smaller fragments using restriction endonucleases DNA fragments are put into wells in a gel and electric currents are passed through the separate the fragments (electrophoresis) Shorter fragments travel further than bigger fragments fragments are transferred to a nylon membrane an alkaline solution is added to make the DNA single stranded they get fixed onto the nylon using UV light DNA probes are added to hybridise to target complementary base sequence via hydrogen bonds any unbound DNA probe is washed off Hybridised DNA probes remian, and allow specific sequences of DNA to be detected The use of fluorescence or auto radiography is used
79
why do smaller fragments of DNA travel further than larger fragments in gel electrophoresis
DNA is negatively charged due to the phisphate groups and is attracted to the positive electrode Shorter travel quicker because they are more easily attracted
80
How would you use a DNA probe to identify a gene in a sample (4 marks)
Extract DNA and add restriction endonucleases Separate the fragments using gel electrophoresis Treat the DNA with alkali to form single strands and expose the bases Add the DNA probe, which will complementary bind to the gene Use auto radiography to identify the bound probe
81

Biology (8 decks)

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