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genetics Flashcards

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1
Q

what is a mutagenic agent?

A

substance that can induce mutation and increase their likelhihood

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2
Q

what is a chromosome mutation?

A

a change in the number or sequence of
genes on a chromosome

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3
Q

what are three types of mutagenic agent?

A
  • virus
  • chemicals
  • radiation
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4
Q

what is a somatic mutation?

A

body cell mutation that only affects one organism and cannot be inherited

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5
Q

what is a germ-line mutation?

A

sex cell mutation that can be passed to future generations

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6
Q

what are 4 methods of mutation?

A
  • insertion/deletion
  • translocation
  • substitution/inversion
  • duplication
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7
Q

what is a translocation chromosome mutation?

A

when a section of a chromosome breaks off and attaches to a different chromosome

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8
Q

what is an inversion chromosome mutation?

A

when a section of a chromosome breaks off and attaches to the same chromosome, but is inverted

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9
Q

why do most mutations not have an effect on us?

A
  • non coding genes aren’t involved in protein synthesis so nothing changes
  • degenerate codes means most mutations produce the same polypeptide
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10
Q

what is the effect of insertion or deletion of a nucleotide?

A
  • new triplet code is created as every nucleotide is shifted
  • now codes for a different polypeptide chain with a different function or no function
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11
Q

what are the 3 types of substitution mutation?

A
  • silent
  • missense
  • nonsense
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12
Q

what is a silent substitution?

A

mutation does not alter the amino acid sequence of the polypeptide due to degenerate code

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13
Q

what is a missense substitution?

A

mutation alters a single amino acid in the polypeptide chain eg. sickle cell anaemia

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14
Q

what is a nonsense substitution?

A

mutation creates a premature stop codon causing the polypeptide chain produced to be incomplete and therefore affecting the final protein structure and function

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15
Q

what is a beneficial mutation?

A

provides a selective advantage eg. sickle cell anaemia helped prevent death by malaria as the protist couldn’t live in the erythrocyte

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16
Q

what is a neutral mutation?

A

has no advantage or disadvantage

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17
Q

what is a harmful mutation?

A

provides a damaging disadvantage to an organism

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18
Q

what are the 3 types of regulatory mechanisms

A
  • transcriptional level
  • post transcriptional level
  • post translational level
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19
Q

what is a structural gene?

A

codes for a protein that has a function within a cell

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20
Q

what is a regulatory gene?

A

code for proteins that control the expression of structural genes

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21
Q

what is a promoter?

A

DNA sequence which sits between the regulatory gene and the first structural gene and is a binding site for RNA polymerase to carry out transcription

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22
Q

what is an operator?

A

segment of DNA to which a repressor binds to inhibit the transcription of a gene

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23
Q

what are the two types of transcription factors?

A

repressor and activator

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24
Q

how does an activator work?

A

binds to the promoter, and if RNA polymerase also binds, transcription occurs

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25
how does a repressor work?
produced by regulatory gene and binds to operator which means that when RNA polymerase binds to operator transcription of structural genes cannot occur
26
what is an operon?
a cluster of structural genes that is under the control of one promoter made of: - cluster of structural genes - promoter - operator
27
what is lac operon composed of?
- LacI (lactose inhibitory gene/regulatory gene) - promoter - LacO (operator) - LacZ,Y,A (structural genes)
28
what happens to gene when there is no lactose present?
lac operon is inactive and repressor successfully binds to operator
29
what happens to the gene when lactose is present?
lac operon is active and when repressor is produced, lactose binds to it and changes its tertiary structure so it cannot bind to the operator and transcription can occur
30
what does a DNA sequence in eukaryotes not contain?
operator
31
what do transcription factors in eukaryotes do differently to in prokaryotes?
stimulate gene expression instead of inhibiting it
32
how are transcription factors in eukaryotes activated?
- hormone diffuses into nucleus - bids to TF and changes the tertiary structure which activates it - can now bind to promoter - RNA polymerase can also bind and transcribe the structural genes
33
what is lac operon an example of?
control at the transcriptional level
34
how do glucose levels in e. coli affect lac operon?
low conc means not enough lactose has been broken down so encourages transcription and vice versa
35
what is upregulation?
enhancing transcription to increase lactose metabolism when glucose levels are low
36
what is the name of the compound used in cells to add a phosphate group to a protein?
cyclic AMP (cAMP)
37
how does upregulation occur?
- CAP binding site just before promoter - CAP (cAMP receptor protein) binds to cAMP to form CAP-cAMP - this binds to CAP binding site which helps RNA polymerase bind to promoter which cause upregulation
38
what is CAP-cAMP binding an example of?
control at the post translational level
39
what are three post-transcriptional events that must occur in order to form mature mRNA from primary mRNA?
- capping - polyadenylation - splicing
40
what is capping?
modified nucleotide (methyl group) "cap" is added to the 5’-end of the transcribed RNA
41
what does the methylated cap do?
- provides protection against degradation of mRNA by exonucleases in the cytoplasm​ - allows the transcribed mRNA to be recognised by the cell’s translational machinery i.e. it helps it to bind to ribosomes
42
what is polydenylation?
the addition of a long chain of adenine nucleotides (a poly-A tail) to the 3’-end of the transcript
43
what does polyadenylation do?
improves the stability of the RNA transcript and facilitates its export from the nucleus
44
what is splicing?
removal of non-coding sequences called introns which gives mature mRNA
45
what are introns and exons?
introns are non coding DNA sections and exons are coding DNA sections
46
how does splicing work?
RNA is cut at specific points to removes introns and leave exons which are then fused together to form a continuous sequence of coding DNA.​ Remember: Exons exit the nucleus
47
what is RNA editing?
addition, deletion or substitution of bases in RNA after it's been generated by RNA polymerase
48
why is RNA editing useful?
increases the range of proteins produced from a single mRNA molecule/gene
49
what are protein kinases?
- post translational control - regulators of cell activity which activated by second messengers such as cAMP - enzymes that catalyse the addition of phosphate groups to proteins. - causes a change in the tertiary structure and hence the protein functionality
50
why might mRNA still not be translated?
degradation: resistant mRNA molecules will last longer in the cytoplasm and thus more proteins will be synthesised binding of inhibitory proteins​: bind to mRNA which prevents it binding to ribosomes and the synthesis of proteins​ activation of initiation factors: factors aid binding of mRNA to ribosomes
51
what is epigenetics?
study of stable cellular and physiological traits that are heritable by daughter cells which results from changes in gene expression that are not due to an alteration in DNA nucleotide sequence
52
what is the structure of a nucleosome?
single nucleosome consists of a portion of double stranded DNA that is wrapped around histone cores(8 subunits)
53
what is a body plan?
observable, spatial arrangement of an organisms body parts
54
what is a homeobox gene?
DNA sequence of around 180 base pairs that regulate large scale anatomical features in early stages of embryonic development and acts as a regulatory gene
55
in which organisms are homeobox genes found?
plants, animals and fungi
56
what type of gene is a homeobox gene?
regulatory gene as it codes for transcription factors
57
what is a homeobox?
sequence within the homeobox gene that codes for the homeodomain in a transcription factor
58
what happens if an organism has a mutation in its homeobox gene/why are homeobox genes highly conserved between organisms?
it wont survive as its body plan wont be correct
59
what are hox genes?
type of homeobox gene that is only found in animals
60
what cellular processes control the development of a body plan?
mitosis and apoptosis
61
what is apoptosis?
programmed cell death to remove cells that are no longer needed
62
what are mitosis and apoptosis controlled by?
hox genes
63
what do hox genes respond to?
- internal stimuli eg. DNA damage - external stimuli eg. stress
64
what is meant by post-transcriptional control?
modification of pre-mRNA or primary mRNA to produce mature mRNA
65
what is meant by post-translational control?
modification of proteins after they have been synthesised.
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