Regulation of Gene Expression

Question 1

Are mRNAs always translated into protein?

Answer 1

no!

Some of them are degraded before they are translated and some of them are translated into protein then modified and/or degraded after that

Depends on how quickly they are being made and destroyed - should be a balance

Question 2

Are mRNA only good once?

Answer 2

The same mRNA transcript can be used multiple times for minutes or hours before it is degraded

Question 3

Which factors can control gene expression in transcription?

Answer 3

regulatory elements

promotors

enhancers

chromatin changes

Methylation of cytosine

Question 4

Which factors control RNA processing?

Answer 4

removal of introns or exons

choice of poly A site

splice sites

transport rate

Question 5

Which factors regulate translation?

Answer 5

ribosome choice

initiation start codon placement

secondary structure of mRNA

RNA protein interactions

poly A tail length

Question 6

What affects mRNA degradation?

Answer 6

specific half-life

mRNA is less stable than rRNA or tRNA

Question 7

What regulates Protein modification and degredation?

Answer 7

modification - assembly of subunits

degradation - ubiquitin - targeted for destruction

N-rule

Question 8

What is the rate limiting step of transcription?

Answer 8

RNA polymerase binding and intitiation

Question 9

True or false

Control of gene expression as is relates to RNA polymerase binding and initiation is highly regulated

Answer 9

True!!!

Question 10

Are promotors Cis or Trans acting?

Answer 10

Cis Acting

Question 11

What do Promotors do?

Answer 11

They direct transcription of genes located on the same strand of DNA

They are bound by basal transcription factors

Question 12

What do Transcription Factors do?

Answer 12

They are free to move around the nucleus and regulate the expression of different genes

Question 13

Are transcription factors cis-acting or trans-acting?

Answer 13

Trans-acting

Question 14

How do you form the initiation complex for Transciption?

Answer 14

1) Transcription factor recognizes promotor regions (TATA box)
2) transcription factor binds to site
3) REcruits more transcription factor
4) RNA polymerase binds and
5) more transcription factors join in

Question 15

Which transcription factor is the most important and why?

Answer 15

TFIIH

It’s important because it functions as helicase - helping to unwind the DNA a this site and kinase because it’s an enzyme that phosphorylates - uses nucleotide to transfer a phosphate to another molecule

Question 16

What’s an enhancer?

Answer 16

DNA sequences that determine how frequently and when transcription occurs

Cis-acting

Can be far away from the promoter too!

Question 17

Does methylation increase or decrease the rate of transcription?

Answer 17

decrease

Question 18

What role do Hormones receptors play in gene expression?

Answer 18

hormones can cause different genes in the nucleus to be activated

Type 1 response - steroids activate it

Type 2 Vit A/D and Thyroid hormones turn it on

They alter the rate of transcription and translation in the cell

Question 19

How do Type 1 Hormone receptors effect Transcription and Translation?

Answer 19

A hormone from outside the cell diffuses accross the membrane into the cytoplasm

Attaches to the receptor in the CYTOPLASM

becomes activated

and inreases the rate of transcription

Question 20

How does a type II hormone receptor work?

Answer 20

1) A hormone from ouside of the cell inters the outer most layer of the cell
2) It enters the nucleus - diffuses
3) Binds to a receptor
4) Becomes activated
5) which increases the rate of transcription

Question 21

Which cells are needed for cell signalling?

Answer 21

cytokines

Question 22

What are cytokines?

Answer 22

small secreted proteins including chemokines and interferons which act to mediate regulate immunity, inflammation, hematopoiesis by cell signally

Question 23

How do cytokines work in cell signalling/

Answer 23

They bind to specific membrane receptors and singal the cell to alter expression