Regulation of Eukaryotic Gene Expression

Question 1

What is the function of RNA polymerase I?

Answer 1

Transcribe genes encoding the production of ribosomal subunits

Question 2

What is the function of RNA polymerase II?

Answer 2

Transcribe all protein-coding genes and a few non protein-coding genes

Question 3

What are housekeeping genes?

Answer 3

Genes that are expressed in all cell types and encode proteins essential for universal cell function

Question 4

How is eukaryotic transcriptional control exerted?

Answer 4

Cis-acting DNA enhancer elements bind specific trans-acting transcription factors

Question 5

What does the binding of trans-acting factors to cis-acting DNA sequences next to a gene stabilise?

Answer 5

This stabilises interactions between general transcription factors and RNA polymerase II with the corresponding promoter

Question 6

What type of transcription factors do steroid hormones bind to that regulate specific gene regulation?

Answer 6

Nuclear hormone receptors

Question 7

Trans-acting transcription factors bind to cis-acting DNA sequences in…

Answer 7

Chromatin

Question 8

What is chromatin?

Answer 8

• Mixture of DNA and histones

- Building blocks of chromatin are nucleosomes

Question 9

How many base pairs per nucleosome?

Answer 9

146 base pairs

Question 10

How can nucleosome affect gene transcription?

Answer 10

Nucleosomes can be covalently modified

Question 11

Chromatin structure

Answer 11

DNA wrapped twice around histone permits efficient packaging but difficult for transcription factors to find target genes

Question 12

Chromatin structure makes it hard for transcription factors to find target genes, how is this resolved?

Answer 12

1. Chromatin remodelling factors

2. Covalent modification of DNA and histones

Question 13

What acts as a flag for remodelling?

Answer 13

Acetylation of lysine

Question 14

How do chromatin remodelling factors work?

Answer 14

Coil and uncoil chromatin fibres

Move histone along DNA

Question 15

Methylation in CpG dinucleotides…

Answer 15

Switches off genes

Question 16

What does the linker histone H1 do?

Answer 16

Fix nucleosomes into position for compaction

Question 17

What is the downside of the linker histone H1?

Answer 17

It limits accessibility of genes for transcription

Question 18

Example of epigenetic changes in an organism

Answer 18

Tortoiseshell cats

Question 19

Three regulatory steps of post-transcriptional controls on gene expression

Answer 19

1. Control of splicing
2. Control of 5’ capping and adenylation
3. mRNA translation

Question 20

What is RNA splicing?

Answer 20

Removal of introns then ligation of consecutive exons

Question 21

How is sex determined in Drosophila?

Answer 21

RNA splicing

Question 22

RNA splicing in Drosophila

Answer 22

Females have transformer protein –> activates spicing

Males, splice site inactive so intron remains unspliced

Question 23

Is splicing activated in male or female Drosophila?

Answer 23

Females

Question 24

What is the 5’ cap?

Answer 24

Methylated guanine residue that is added to the first nucleotide of every eukaryotic mRNA

Question 25

What is the 5’ cap required for?

Answer 25

Initiating translation and also limits degradation

Question 26

Regulation of translation of mRNA coding for ferritin

Answer 26

Regulated by [iron]
Low [iron]: hair pin formed in ferritin mRNA by H bonds and aconite binds –> inhibits translation
High [iron]: aconite dissociates and binds to excess iron –> translation of ferritin mRNA can occur

Question 27

What is ferritin?

Answer 27

Iron storage protein found in blood

Question 28

How does a low free iron concentration affect ferritin mRNA translation?

Answer 28

Hair pin formed in ferritin mRNA by H bonds and aconitase binds –> inhibits translation