3.8.1 genes

Question 1

what are the different types of mutations?

Answer 1

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

Question 2

how do gene mutations occur

Answer 2

spontaneously

Question 3

what is a gene mutation

Answer 3

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

Question 4

what is a mutagenic agent?

Answer 4

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

Question 5

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

Answer 5

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

Question 6

explain what degenerate means

Answer 6

more than one codon can code for each amino acid

Question 7

explain a positive effect of mutations

Answer 7

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

Question 8

what is a substitution mutation

Answer 8

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

Question 9

what is a deletion mutation

Answer 9

one or more bases are removed causing a frameshift

Question 10

what is an addition mutation

Answer 10

one or more bases are added causing a frameshift

Question 11

what is a duplication mutation

Answer 11

one or more bases are repeated

Question 12

what is an inversion mutation

Answer 12

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

Question 13

what is a translocation mutation

Answer 13

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

Question 14

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

Answer 14

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

Question 15

explain what a frameshift mutation does

Answer 15

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

Question 16

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

Answer 16

introns

Question 17

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

Answer 17

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.

Question 18

what is a silent mutation

Answer 18

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

Question 19

explain the effect of a frameshift mutation

Answer 19

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.

Question 20

what is a stem cell

Answer 20

an undifferentiated cell that continually divides

Question 21

what is a totipotent cell

Answer 21

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

Question 22

what is a pluripotent cell

Answer 22

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

Question 23

how does a cell become specialised

Answer 23

only translates part of their DNA

Question 24

what is a multipotent cell

Answer 24

can differentiate into a limited number of cells

Question 25

whats a unipotent cell

Answer 25

can only differentiate into one type of cell

Question 26

where are adult stem cells found

Answer 26

bone marrow

Question 27

suggest why its better to use IPS cells than pluripotent cells

Answer 27

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.

Question 28

what is a genome

Answer 28

total number of genes in DNA in an organism

Question 29

explain why antibody binds to transcription factor

Answer 29

antibody is complimentary to specific tertiary strcuture

Question 30

what is a transcription factor

Answer 30

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

Question 31

why is oestrogen a transcription factor

Answer 31

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

Question 32

oestrogen only affects target cells. explain why

Answer 32

not all cells have specific oestrogen receptors

Question 33

what is oestrogen

Answer 33

lipid soluble steroid hormone

Question 34

define epigenetics

Answer 34

heritable changes in gene function that dont change DNA base sequence

Question 35

what is a epigenome

Answer 35

single layer of chemical tags on the DNA

Question 36

what is methylation of DNA

Answer 36

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

Question 37

what is acetylation

Answer 37

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

Question 38

what is siRNA

Answer 38

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

Question 39

how does sirna prevent transcription

Answer 39

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

Question 40

how can hypermethylation lead to cancer (epigenetics)

Answer 40

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.

Question 41

what does a tumour suppressor gene do

Answer 41

codes for a protein that slows cell division and regulates mitosis

Question 42

give an example of a TSG

Answer 42

BRCA-1

Question 43

what are proto-oncogenes

Answer 43

produce a protein that stimulates cells to divide

Question 44

what is hyperacetylation

Answer 44

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

Question 45

what are oncogenes

Answer 45

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

Question 46

how do oncogenes occur

Answer 46

random mutations or due to carcinogens such as exposure to UV

Question 47

what is cancer

Answer 47

uncontrollable cell division

Question 48

how can mutations cause cancer

Answer 48

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

Question 49

whats the difference between benign and malignant

Answer 49

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

Question 50

what is metastasis

Answer 50

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

Question 51

how can tumours cause harm to the body

Answer 51

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

Question 52

what is an activator

Answer 52

helps rna polymerase bind at the promoter region to allow transcription

Question 53

what is a repressor

Answer 53

binds to promoter region and prevents rna polymerase from binding

Question 54

wat is an inhibitor molecule

Answer 54

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

Question 55

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

Answer 55

degenerate code. mutation in intron

Question 56

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

Answer 56

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