gene expression and regulation

Question 1

how are stem cells used to treat human disorders

Answer 1

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

Question 2

what’s a transcriptional factor

Answer 2

proteins that regulate transcription of specifc target genes in eukaryotes
by binding to specific dna base seq on promoter region

Question 3

how is transcription regulated using transcription factors

Answer 3

TF move from cyto to nuclues
bind to dna at specific dna base seq on promoter region
stimulates or inhibits transcriptionof target genes by helping or preventing rna polymerase binding

Question 4

oestrogen affect on transcription

Answer 4

lipid soluble hormone diffuses into cell across phospholipid bilayer
in cyto - oestrogen binds to its receptor an inactive TF forming oestrogen receptor complex
chances shape of inactive TF forming active TF
complex diffuses from cyto to nucleus
then binds to specific dna base seq on promoter region of target gene
stimulating transcription of target genes forming mrna by helping rna polymerase bind

Question 5

epigenetic

Answer 5

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

Question 6

epigenome

Answer 6

all chem modifications of dna and histone protiens
methyl groups on dna and acetyl on histones

Question 7

methylation

Answer 7

increased meth of dna
methyl groups added to cytosine bases in dna
nucleosomes pack together more tightly
preventing TF and rna polymerase binding to promoter

Question 8

acetylation

Answer 8

decreases acetylation of histones
increases positive charge of histones
bind to dna more tightly
preventing TF and rna polymerase binding to promoter

Question 9

what’s RNA interference

Answer 9

inhibition of translation of mrna produced from target genes by rna molecules
inhibits expression of target gene

Question 10

regulation of translation by rna interference

Answer 10

siRNA miRNA binds to a protein, forming an RNA-induced silencing complex (RISC)
siRNA synthesised as double-stranded RNA → 1 strand incorporated
miRNA synthesised as a double-stranded hairpin bend of RNA →both strands incorporated
miRNA / siRNA within RISC binds to target mRNA with a complementary base sequence
This leads to hydrolysis of mRNA into fragments which are then degraded OR prevents ribosomes binding
preventing translation of target mRNA into protein

Question 11

how does tumour form

Answer 11

mutation in dna or gene controlling mitosis
uncontrolled cell division
tumour if it results in mass of abnormal cells

Question 12

the function of tumour suppressor genes

Answer 12

code for protiens that
inhibit or slow cell cycle
or cause self destruction of potential tumour cells

Question 13

Explain the role of tumour suppressor genes in the development of tumours

Answer 13

Mutation in DNA base sequence production of non-functional protein
○ By leading to change in amino acid sequence which changes protein tertiary structure
● Decreased histone acetylation OR increased DNA methylation → prevents production of protein
○ By preventing binding of RNA polymerase to promoter region, inhibiting transcription
● Both lead to uncontrolled cell division (cell division cannot be slowed)

Question 14

prot ooncogene

Answer 14

code for protiens that stimulate cell division

Question 15

oncogene in development of tumour

Answer 15

mutation of proto oncogene
mutation in dna base sequence overproduction of protein or perm activated by leading to change in AA seq changing protein tertiary structure
decreased dna meth or increased acetylation
increased production of protein
stimulated rna polymerase to bind to promoter region so stim transcription
uncontrolled cell division

Question 16

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

Answer 16

Some breast cancers cells have oestrogen receptors, which are inactive transcription factors
oestrogen concentration is increased, more oestrogen binds to oestrogen receptors,
forming more oestrogen-receptor complexes which are active transcription factors
3. These bind to promoter regions of genes that code for proteins stimulating cell division
4. This increases transcription increasing the rate of cell division