Gene expression

Question 1

What is gene expression

Answer 1

The process where information from DNA is used in the synthesis of a functional gene product

Question 2

Why is gene expression important

Answer 2

As all somatic cells contain all DNA so different cell types need to express different genes to perform their functions, respond to their environment and conserve energy so that genes are only expressed where and when they are needed

Question 3

What is the promoter in a gene

Answer 3

The region that regulates gene expression

Question 4

What is the RNA coding sequence of a gene

Answer 4

Region which is used to synthesise mRNA

Question 5

What is meant by ‘position 1+’ on a gene

Answer 5

The transcription start site

Question 6

How are positions on the gene labelled upstream and downstream from the +1 site

Answer 6

Upstream= - (Position before 1+ start site)
Downstream= + (position after 1+ start site)

Question 7

What is a consensus sequence

Answer 7

Known sequence in promoter region that will be recognised by specific transcription factors

Question 8

What is the regulatory promoter

Answer 8

Combination of consensus sequences in the promoter region that affects the level of transcription e.g.number of RNA molecules produced, by affecting the stability of basal transcription machinery

Question 9

What is the core promoter

Answer 9

The site in the promoter region immediately upstream the transcription start site (1+) that is recognised by basal transcription machinery

Question 10

What are the ‘core machinery’

Answer 10

RNA polymerases and proteins that form initiation complexes

Question 11

What are the specific factors

Answer 11

proteins that induce or repress expression of selective genes

Question 12

What is constitutive gene expression

Answer 12

Gene expression transcribed in all cells continually

Question 13

What is regulated gene expression

Answer 13

Expression induced or repressed by specific factors

Question 14

What are constitutive (unregulated) genes

Answer 14

‘Housekeeping’ genes that are always expressed within a cell at all times in the absence of a repressor or activator and are transcribed at a fixed rate at all times

Question 15

What are inducible (regulated) genes

Answer 15

Genes that only need to be expressed at certain times in specific cells so their expression is induced by specific TFs

Question 16

What are repressible (regulated) genes

Answer 16

Genes that only need to be turned off as needed, their expression is repressed by specific transcription repressors

Question 17

What three levels is gene expression regulated at in eukaryotes

Answer 17

DNA structure, RNA level and protein level and activity

Question 18

What is the function of regulatory mechanisms

Answer 18

Selective gene expression

Question 19

How is gene expression regulated at DNA structure level

Answer 19

Changes in chromatin structure/ how condensed chromatin is

Question 20

How is gene expression regulated at RNA level

Answer 20

Transcription factors, mRNA processing e.g. splicing and alternative splicing and RNA stability

Question 21

How is gene expression regulated at protein level

Answer 21

Translation and post-translational modifications

Question 22

How does chromatin regulate gene expression

Answer 22

Epigenetic mechanisms modify the way DNA is wrapped around histones in chromatin, genes are silenced in regions where chromatin is condensed p/ compact (heterochromatin) as RNA polymerase cannot access the gene, enzymes can modify histones or DNA to alter RNA pol access

Question 23

How do transcription factors regulate gene expression

Answer 23

Turn on or off gene expression at certain times/ in certain cells by binding to the specific consensus sequence, which can impact RNA level/number by stabilising or recruiting RNA pol to promoter or modifying the interaction between DNA and histones

Question 24

What are enhancer sequences

Answer 24

DNA sequences located in the gene promoter that are recognised by activators and further control transcription by triggering the bending of DNA

Question 25

What are activator proteins

Answer 25

Proteins that recognise and bind to enhancer sequences and further influence transcription/RNA level by triggering the bending of DNA

Question 26

How does the bending of DNA due to activators and enhancers influence RNA level/transcription

Answer 26

The bending brings the activator closer to the promoter where the TF and transcription initiation complex is to induce RNA polymerase the transcribe the RNA

Question 27

How does nutrition influence gene expression

Answer 27

Nutrients can play a key role in regulation of gene expression such as by epigenetic regulation e.g folate and TF regulations e.g. vitamin D

Question 28

How does vitamin D stimulate gene expression

Answer 28

• enters target cell and binds to VDR receptor (vitD receptor)
• VDR-vitD complex binds to retinoid X receptor (RXR)
• VDR/RXR complex binds to vitD response element (VDRE) which is a consensus sequence in promoter of vit D responsive genes
• this binding attracts coactivator proteins that bridge with RNA pol II and other proteins in the initiation complex around the TATA box
• transcription is initiated

Question 29

What is the effect of vitamin D on gene expression on the body

Answer 29

Cellular response of increased calcium absorption in the gut, calcium deposition in the bone and calcium reabsorption in the kidney

Question 30

What are epigenetic regulations of gene expression

Answer 30

Changes to gene that are not carried out by DNA (not genetic)