8.1

Question 1

gene mutation

Answer 1

change in base sequence of dna
arise spot during dna replication

Question 2

mutagenic agent

Answer 2

increase the rate of mutation
ultraviolet

Question 3

gene mutation leading to production of non functional enzyme

Answer 3

change in base sequence of dna
change in sequence of amino acids in encoded polypeptide
change in position of ionic hydrogen and disulphides
change in tertiary strcutre of protein
enzymes active site changes shape and substrate cant bind so not ESC form

Question 4

why do some gene mutations not affect order of amino acids

Answer 4

some mutation only change one triplet code so could still code for same amino acid
as genetic code degenerate
some occur in introns which don’t code for amino acids

Question 5

why is change in amino acid sequence not always harmful

Answer 5

may not change tertiary structure of protein if position of bonds don’t change
may positively change properties giving organism selective advantage

Question 6

frameshift

Answer 6

when gene mutation change the number of nucleotides by number not divisible by 3
so dna triplets downstream from mutation changes
The sequence of amino acids encoded changes accordingly and
the effects on the encoded polypeptide are significant

Question 7

stem cells

Answer 7

undifferentiated cells capable of
dividing by mitosis to replace themselves or differentiate into other types of cell

Question 8

how do stem cells become specialised during development

Answer 8

stimuli lead to activation of some genes
mana is transcribed from these genes only
these protiens modify the cell permanently and determine their cell structure and function

Question 9

totipotent

Answer 9

limited time in early mammalian embryo
can divide and differentiate into any type of cell

Question 10

pluripotent

Answer 10

found in mammalian embryos
can divide and differentiate into most types of cell not placenta

Question 11

multipoint cells

Answer 11

in mature mammals
can divide and differentiate into a limited number of cells

Question 12

unipotent

Answer 12

found in mature mammals
divide and differentiate into one type of cell cardiomyocytes

Question 13

stem cells in treatment of human disorder

Answer 13

transplanted into patient
divide in unlimited numbers
then differentiate into required healthy cells

Question 14

example of using stem cells

Answer 14

treating type 1 diabetes by creating healthy islet cells that produce insulin
bone marrow stem cell transplant for blood cancers
destroy patients bone marrow before treatment so no faulty cells produced
transplant cells from healthy person which divide and differentiate into healthy cells

Question 15

how are IPS produced

Answer 15

obtain adult somatic cells from patient
add specific tf associated with pluripotency to cells so they express genes associated with pluripotency
TF attach to promoter region of dna stimulates or inhibits transcription
culture cells to allow them. to divide by mitosis

Question 16

for use of stem cells

Answer 16

can divide and differentiate into required healthy cells
relieve human suffering by saving life and improving quality of life
embryos left after IVF and would otherwise be destroyed
IPS unlikely to be rejected since made from patients own cells

Question 17

against the use of stem cells

Answer 17

obtaining requires destruction of embryo and potential life
immune system could reject cells
immuno depressant drugs required
cells could divide out of control leading to formation of cancer

Question 18

TF

Answer 18

proteins which regulate transcription of specific target genes in euk
bind to specific dna base sequence on promoter region

Question 19

how can transcription be regulated using TF

Answer 19

TF move from cytoplasm to nucleus
bind to dna at specific dna base sequence on promoter region
stimulating or inhibiting transcription of target genes by helping or preventing dna polymerase binding

Question 20

how oestrogen affects transcription

Answer 20

oestrogen - lipid soluble steroid hormone so diffuse into cell across phospholipid bilayer
in cytoplasm oestrogen binds to its receptor - an inactive TF forming an oestrogen receptor complex
changes shape of inactive TF forming an active TF
complex diffuses from cytoplasm to nucleus and binds to a specific dna base sequence on promoter region of target gene
stimulating transcription of target genes forming mRNA by helping RNA polymerase binding

Question 21

why does oestrogen only affect target cells

Answer 21

other cells dont have oesteogen receptors

Question 22

epigenome

Answer 22

all chemical modifications of DNA and histone protiens
methyl groups on DNA
acetyl groups on histone

Question 22

what does increased methylation do to dna

Answer 22

inhibits transcription

Question 22

epigenetics

Answer 22

heritable changes in gene function without change in dna base sequence
caused by changes in the environment

Question 23

what does increased acetylation of histones do to transcription

Answer 23

allows transcription

Question 24

how does methylation inhibit transcription

Answer 24

increased methylation of DNA
methyl groups added to cytosine bases in dna
so nuleosomes pack more tightly together
preventing transcription factors and rna polymerase binding to promoter

Question 25

how does decreased acetylation can inhibit transcription

Answer 25

decreased acetylation of histones increasing the positive charge on histones
so histones bind to dna more tightly
prevent TF and RNA polymerase binding to promoter

Question 26

epigenetic relevance on disease development and treatment

Answer 26

environmental factors = epigenetic changes
stimulate or inhibit transcription of certain genes leading to disease development
increased methylation or decreased acetylation inhibit transcription
diagnostic test detect epigenetic change before symptoms develop
drugs to reverse epigenetic changes

Question 27

rna interference

Answer 27

inhibition of translation of MRNA produced from target genes by RNA molecules
inhibiting expression of target gene

Question 28

regulation of translation by RNA interference

Answer 28

siRNA or miRNA bind to protein
= RNA induced silencing complex
siRNA synth as double stranded RNA so 1 strand incorporated
miRNA synthesised as double stranded hairpin loop of dna so both strands incorporated
single stranded miRNA\siRNA within RISC bind to target mRNA with comp base sequence
leads to hydrolysis of mrna = fragments - degraded or prevent ribosomes binding
reducing translation of target mRNA to protein

Question 29

how do tumours and cancers form

Answer 29

mutation in gene controlling mitosis
uncontrolled cell division

Question 30

benign

Answer 30

slow growth
well differentiated
normal nuclei
don’t spread by metastasis
normally removed by surgery and rarely return

Question 31

malignant

Answer 31

grow faster
poorly differentiated
irregular dark nuclei
spread by metastasis
removed by surgery combined with chemo but often return

Question 32

function of tumour suppressor gene

Answer 32

code for protiens that inhibit and slow cell cycle
cause send destruction of potential tumour cells

Question 33

role of tumour supressor genes in development of tumour

Answer 33

mutation in dna base sequence
= non functional protein
by leading to change in AA sequence changing protein tertiary structure
decreased histone acetylation or increased dna methylation prevent production of protein by preventing rna polymerase binding Inhibit transcription
both lead to uncontrolled cell division

Question 34

proto oncogene function

Answer 34

code for proteins stimulating cell division

Question 35

oncogene in development of tumour

Answer 35

mutated form of corresponding protooncogene
mutation in dna base sequence = overproduction of protein or permanently activated protein
by leading to change in aa sequence which changes protein tertiary structure
decreased dna methylation or increased histone acetylation increase production of protein by stimulating rna polymerase binding stimulating transcription
leads to uncontrolled cell division

Question 36

Suggest why tumours require mutations in both alleles of a tumour
suppressor gene but only one allele of an oncogene

Answer 36

one functional allele of TSG produce enough protein to slow cell cycle so cell division controlled
one mutated oncogene alelle produce enough protein to lead to rapid uncontrolled cell division

Question 37

epigenetic relevance in cancer treatment

Answer 37

increased dna methylation or decreased histone acetylation of oncogene
inhibit transcription
vice versa

Question 38

Explain the role of increased oestrogen concentrations in the development
of some (oestrogen receptor-positive) breast cancers

Answer 38

some great cancer have oestrogen receptors
these are inactive TF
oestrogen conc increase more oestrogen binds to oestrogen receptors
more oestrogen receptor complex which are active TF
these bind to promoter region of genes that code for protiens stimulating cell division
increases transcription of these genes and cell division

Question 39

Suggest how drugs that have a similar structure to oestrogen help treat
oestrogen receptor-positive breast cancers

Answer 39

Drugs bind to oestrogen receptors (inactive transcription factors), preventing binding of oestrogen
fewer transcription factors bind to promoter regions of genes that stimulate the cell cycle

Question 40

structure of dna to its functions

Answer 40

sugar phosphate backbone and double stranded providing strength
long and large molecule so it can store lots of info
helical so its compact
base sequence allows info to be stored
double stranded so replication can occur semi conservatively
weak hydrogen bonds so it can be unzipped
in replications
lots of hydrogen bonds - strength in numbers

Question 41

suggest why a drug that can kill cancer cells isn’t given more frequently

Answer 41

it binds to healthy cells too
so too many healthy cells killed
person will have side effects and they may die