Gene Regulation

Question 1

Cellular environment is dynamic

Answer 1

It is advantageous to use
available resources in most
efficient way Gene expression is dynamic
and changes with age, after
pharmacological treatment, and
during disease

Question 2

What are promotor sequences

Answer 2

DNA sequences that define where transcription of a gene y RNA polymerase begins
They define the direction of transcription and indicate which dna strand will be transcribed

Question 3

First stage in transcription?

Answer 3

Initiation stage : RNA polymerase recognised the promotor and starts to transcribe

Question 4

What is the second phase of transcription

Answer 4

Elongation stage : RNA strand is continuously growing

Question 5

What is the last stage of transcription

Answer 5

Termination phase : RNA polymerase stops synthesis and te nascent RNA is separated from DNA template

Question 6

What is a repressor

Answer 6

A protein that inhibits expression of a gene. It may act to prevent transcription by binding to an operator site inDNA or to prevent translation by binding to RNA

Question 7

What is an operator in gene regulation

Answer 7

The operator is the site on DNA at which a repressor protein binds to prevent transcription from initiating at the adjacent promoter

Question 8

Eukaryotic trasncription

Answer 8

In eukaryotes there are 3 RNA polymerases (Pol 1 pol 2 pol 3)
All proteins coding enes are transcribed by RNA pol 2
Pol 1 transcribes the ribosomal RNA genes
Pol 3 transcribes transfer RNA genes

Question 9

What is a promotor sequence

Answer 9

A promotor is a sequence of DNA needed to turn a gene on or off
Transcription is initiated at the promotor
Usually found near the beginning of a gene the rot has binding site from transcription factor

Question 10

What is a TATA box

Answer 10

A TATA box is a DNA sequence that indicates where a genetic sequence can be decoded

Question 11

What are enhancers in eukaryotic trancription

Answer 11

Enhancers affect transcription these sequences occur upstream, downstream and within introns
Enhancers dono act on the promotor region itself, but are bound by transcription factors

Question 12

What are silencers in eukaryotic transcription

Answer 12

They are enhancers that repress transcription instead of increasing it

Question 13

General and promotor specific transcription factors

Answer 13

• enteral TF are active in most cell types
• promotor specific TF can influence transcription positively or negatively
• promotor specific F may be expressed in a. Tissue specific manner

Question 14

General TF

Answer 14

General TF bind to a DNA promotor sequence near the transcription start se and help from the transcription initiation complex

Question 15

Activators

Answer 15

These proteins bind to genes at sites known as enhancers. Activators help determine which genes will be switched on and they seed the rate of transcription

Question 16

Basal transcription factors

Answer 16

In response to injunctions from activators, these factors position RNA polymerase a the start of the protein coding region of a gene and send the enzyme on its way

Question 17

Gene regulation at chromatin level

Answer 17

DNA tightly wrapped around the histones is inaccessible to RNA polymerase
Chromatin remodelling must occur to slide the nucleosomes along he DNA to expose the promotor region

Question 18

Chromatin remodelling

Answer 18

Chromatin must “open” in order for gene expression to take place. This process of “opening” is called chromatin remodelling

Question 19

What are the levels of gene regulation?

Answer 19

• alteration of gene structure
• transcriptional control ( whether RNA is created or not)
• mRNA processing ( post-transcriptional modifications
• stability of RNA
• translational control