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biology > 3.8.1 genes > Flashcards

3.8.1 genes Flashcards

alteration of the sequences of bases in dna

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1
Q

what are the different types of mutations?

A

addition, deletion, substitution, inversion, duplication and translocation.

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2
Q

how do gene mutations occur

A

spontaneously

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3
Q

what is a gene mutation

A

a change in the sequence or structure of base pairs in DNA that can alter the structure of proteins

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4
Q

what is a mutagenic agent?

A

a physical or chemical factor that increases the mutation rate, eg radiation exposure, alcohol etc

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5
Q

why is it important that dna is proofread and when does it occur

A

to stop mistakes being made during the cell cycle and occurs during the s phase of dna replication

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6
Q

explain what degenerate means

A

more than one codon can code for each amino acid

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7
Q

explain a positive effect of mutations

A

they can increase survival and reproduction rate compared to others in their species

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8
Q

what is a substitution mutation

A

one or more bases are swapped for another (eg. CGG to GGG)

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9
Q

what is a deletion mutation

A

one or more bases are removed causing a frameshift

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10
Q

what is an addition mutation

A

one or more bases are added causing a frameshift

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11
Q

what is a duplication mutation

A

one or more bases are repeated

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12
Q

what is an inversion mutation

A

a sequence of bases is reversed (eg. 2315 to 5132)

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13
Q

what is a translocation mutation

A

a piece of one chromosome breaks of and reattaches to another chromosome

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14
Q

what types of mutation are most likely to have no amino acid change and why

A

inversion and substitution because they only change one base and due to degenerate nature it could code for the same amino acid

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15
Q

explain what a frameshift mutation does

A

they change the number of bases in dna code so all codons that follow shift and sre changed so dna is transcribed different

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16
Q

what name is used for the non coding sections of a gene

A

introns

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17
Q

explain how deletion/ addition mutations can lead to a non-functional protein/enzyme

A

mutation changes base sequence in dna which causes a frameshift in amino acid sequence so tertiary structure of protein can change and enzyme substrate complexes may not be able to form.

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18
Q

what is a silent mutation

A

a change in the nucleotide sequence that results in the same amino acid sequence.

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19
Q

explain the effect of a frameshift mutation

A

can cause a non-functioning polypeptide. change in the base sequence can change the tertiary structure of a protein. if its an enzyme, active site can change so ES complexes can no longer form.

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20
Q

what is a stem cell

A

an undifferentiated cell that continually divides

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21
Q

what is a totipotent cell

A

can differentiate into any type of body cell. available for a limited time in embryo cells

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22
Q

what is a pluripotent cell

A

can differentiate into any type of cell. found in embryos fromday 4-16

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23
Q

how does a cell become specialised

A

only translates part of their DNA

24
Q

what is a multipotent cell

A

can differentiate into a limited number of cells

25
Q

whats a unipotent cell

A

can only differentiate into one type of cell

26
Q

where are adult stem cells found

A

bone marrow

27
Q

suggest why its better to use IPS cells than pluripotent cells

A

they are adult somatic cells manipulated to express TF that are usually expressed by pluripotent cells without destroying the embryo. no cloning, no risk of rejection.

28
Q

what is a genome

A

total number of genes in DNA in an organism

29
Q

explain why antibody binds to transcription factor

A

antibody is complimentary to specific tertiary strcuture

30
Q

what is a transcription factor

A

a protein that binds to DNA at promoter region, preventing or allowing transcription

31
Q

why is oestrogen a transcription factor

A

diffuses through membrane to nucleus. attaches to oestrogen receptor to form a complex which changes tertiary structure. it then binds to promoter region to increase transcription and allow rna polymerase to bind

32
Q

oestrogen only affects target cells. explain why

A

not all cells have specific oestrogen receptors

33
Q

what is oestrogen

A

lipid soluble steroid hormone

34
Q

define epigenetics

A

heritable changes in gene function that dont change DNA base sequence

35
Q

what is a epigenome

A

single layer of chemical tags on the DNA

36
Q

what is methylation of DNA

A

addition of a methyl group to cytosine. causes coiling and prevents TF and enzymes from binding so genes are turned off

37
Q

what is acetylation

A

addition of an acetyl group on histones. DNA and acetyl are both negatively charged so repel so DNA loosens making DNA more accessible for TF to bind so transcription can occur

38
Q

what is siRNA

A

a small, double stranded molecule that binds to mrna. it has complimentary bases to mrna

39
Q

how does sirna prevent transcription

A

binds to mrna by complimentary base pairing and cuts mrna which stops translation

40
Q

how can hypermethylation lead to cancer (epigenetics)

A

causes DNA to coil so TF and rna polymerase cannot access dna so tumour suppressor cannot be transcribed to produce protein that slows cell division leading to tumour.

41
Q

what does a tumour suppressor gene do

A

codes for a protein that slows cell division and regulates mitosis

42
Q

give an example of a TSG

A

BRCA-1

43
Q

what are proto-oncogenes

A

produce a protein that stimulates cells to divide

44
Q

what is hyperacetylation

A

causes DNA to loosen which can lead to overexpression. they can mutate to become oncogenes or can lead to cancer due to uncontrllable cell division

45
Q

what are oncogenes

A

mutated genes that cause cancer by causing proteins that stimulate cell division to be constantly activated. cell cycle is sped up

46
Q

how do oncogenes occur

A

random mutations or due to carcinogens such as exposure to UV

47
Q

what is cancer

A

uncontrollable cell division

48
Q

how can mutations cause cancer

A

change base sequence of DNA causing a non functional protein which can lead to uncontrollable cell division

49
Q

whats the difference between benign and malignant

A

benign: non cancerous, slow growing, doesnt spread to other parts of the body
malignant: cancerous, fast growing, spread to other parts of the body

50
Q

what is metastasis

A

when tumours break off and spread to other parts of the body and can develop their own blood supply and oxygen.

51
Q

how can tumours cause harm to the body

A

put pressure on organs. could damage organs. can cause blockages

52
Q

what is an activator

A

helps rna polymerase bind at the promoter region to allow transcription

53
Q

what is a repressor

A

binds to promoter region and prevents rna polymerase from binding

54
Q

wat is an inhibitor molecule

A

can bind to TF, preventing it from binding to promoter region

55
Q

not all mutations result in a change in the amino acid of the encoded polypeptide. why

A

degenerate code. mutation in intron

56
Q

how can a mutation in the tumour suppressor gene result in a tumour

A

mutation causes gene to be inactivated so doesnt produce protein to slow down cell division which leads to uncontrollable cell division.

biology (8 decks)

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