jean exzprezion

Question 1

What are housekeeping genes

Answer 1

genes are expressed in all cells at constant levels

Question 2

What can expression of non housekeeping genes depend on

Answer 2

on tissue, developmental stage and intra/extracellular signals (e.g. hormones

Question 3

What does changing gene expression do to Polymerase

Answer 3

changes ability of RNA polymerase to bind promoter

Question 4

How is bacterial transcription initiated

Answer 4

nding of sigma factor to promoter, which enables RNA polymerase to bind to promoter to form preinitiation complex

Question 5

What determines is sigma factor binds promoter

Answer 5

• Complementarity to promoter region
• Type of sigma factor
• Repressor/activator protein (affect ability of RNA polymerase to bind to promoter, because prokaryotic DNA is naked.)

Question 6

How is bacterial DNA organised

Answer 6

organised into operons – sets of genes under control of one promoter (e.g. lac operon)

Question 7

Are there operons in eukaryotic DNA

Answer 7

No

Question 8

Describe structure of operon

Answer 8

contain regulatory DNA sequences (e.g. promoter) that control transcription of the operon, sequences are binding sites for regulatory proteins, which control how much the operon is transcribed

Question 9

Describe 2 regulatory proteins that control gene expression

Answer 9

Repressor

Activator

Question 10

What does repressor do

Answer 10

• Binds to DNA section called operator

- reduces transcription (e.g., by blocking RNA polymerase from moving forward on the DNA

Question 11

What does activator do in bacterior

Answer 11

bound to its DNA binding site, it increases transcription of the operon

Question 12

How does chromatin contribute to controlling gene expression of genes

Answer 12

Not all DNA readily accessible, some genes constitutively repressed.

Question 13

Effect of DNA methylation, give example

Answer 13

Chromatin more compact and less accessible. TSGs often silenced in cancer cells by hypermethylation.

Question 14

What happens in DNA methylation

Answer 14

: metyhtransferase converts cytosine to 5-cytosine, methyl group disrupts binding of proteins needed for transcription

Question 15

Describe structure of heterochromatin

Answer 15

more condensed due to methylation

Question 16

Describe structure of euchromatin, and its effect on DNA structure

Answer 16

. Lysine residues of histone tails acetylated . Acetylation can neutralise the positive charge of the histone tail ,so -ve charged DNA less tightly wrapped around histone/nucleosome and more accessible

Question 17

What can euchromatin recruit because of DNA being less tightly wound

Answer 17

chromatin remodelling complexes (shift nucleosomes and induce conformational changes in chromatin) and TATA box binding protein associated factors (which recruit other factors for transcription)

Question 18

What are core promoters

Answer 18

regions in front of genes allowing polymerase to recognise beginning of gene.

Question 19

What does RNA polymerase need to associate promoter sequence

Answer 19

General transcription factor

Question 20

How do GTFs work

Answer 20

• GTF recognises specific sequences – i.e. the promoters, binds promoter sequence creates scaffold then correct polymerase is recruited onto a protein scaffold

Question 21

Does polymerase recognise promoter itself

Answer 21

NO

Question 22

How can specific polymerase get recruited to promoter

Answer 22

Each promoter recognised by different subtype of GTF #

Question 23

What is combinatorial control

Answer 23

many TFs work together, recruit proteins to form transcriptional complex at promoter allowing RNA pol to bind

Question 24

Does RNA polymerase recognise DNA sequence itself in bacteria

Answer 24

Yes

Question 25

How can TF act in a trans manner

Answer 25

- recruit other regulatory proteins expressed by the cell. - These complexes bind to the gene and increase accessibility of initiating site to RNA polymerase. -can affect genes far away in genome.

Question 26

what is TATA sequence

Answer 26

- TATA box is a sequence of DNA found in the core promoter region - TATA binding protein binds, initiates formation of basal transcription complex.

Question 27

What do activators and coactivators ensure

Answer 27

correct and regulated expression of genes – in response to tissue specific and proliferation cues.

Question 28

Where do activators and coactivators bind

Answer 28

regions outside the core promoter elements.

Question 29

What are TFs

Answer 29

• Proteins that bind to promoters or other regulatory DNA regions to increase/decrease gene expression

Question 30

Describe distal regulatory elements position and role

Answer 30

- contribute to regulation of activation of gene - regions can be megabases away, trans acting TFs alter transcription of distant genes, by binding far away from core promoter (e.g. in distal regulatory elements) through DNA protein and protien protein interactions

Question 31

How can enhancers activate promoter region that is far away

Answer 31

associate with protein (same TF as promoter), protein can grab DNA, fold It by protein protein interactions forming loops – brings certain regions of DNA closer together, allows enhancer and promoter to interact - , activate transcription complex on promoter allows RNA polymerase to transcribe

Question 32

What does silencer do

Answer 32

Switch off promoter, negative effect on transcription

Question 33

What does insulator do

Answer 33

only activates promoter to right not left, limits how enhancer affects gene expression.

Question 34

What are the components of distal regulatory elements

Answer 34

Locus controlling region Insulator Silencer Enhancer

Question 35

Example of extracellular substance that controls gene expression

Answer 35

Hormone

Question 36

How can hormone regulate gene expression

Answer 36

- Lipid soluble hormone diffuses into cells binding to receptors inside cells, hormone receptor complex diffuse into nucleus binding to receptor elements in DNA

Question 37

How are some TFs cis acting

Answer 37

bind promoter regions: GC box, CAAT box, TATA box | acting on gene immediately following promoter region

Question 38

Describe eukaryotic promoter region

Answer 38

core promoter, proximal promoter and distal regulatory elements/distal promoter. The DNA has the capability to fold back on itself. This also explains the fact that, the effect of many regulatory sequences take place even though they are located many kilobases away from the site of transcription

Question 39

Why is TATA box important promoter element

Answer 39

binding of transcription factor proteins to the TATA box assists in the binding of RNA polymerase, which then results in the formation of transcription complex.

Question 40

How can TATA box be inhibited

Answer 40

This process will be inhibited when histone proteins get bound to the TATA box.

Question 41

How in transcription achieved in eukaryotes

Answer 41

- promoter that involves in transcription is identified by sigma factor. - Each single sigma factor would recognize a single core promoter sequence - Both RNA polymerase and the sigma factor collectively identify the correct promoter region and form the transcription complex.

Question 42

What is core promoter

Answer 42

minimal portion of the promoter required to properly initiate transcription

Question 43

What do core promoter, proximal and distal regulatory elements contain

Answer 43

transcription factor binding sites

Question 44

What is needed before RNA polymerase can work in eukaryotic cells

Answer 44

transcription factor and its associated transcription mediator complex must be attached to a DNA binding site called a promoter region