Introduction to control of gene expression

Question 1

What do all humans cell have the same?

Answer 1

Human cells have the same genetic blueprint which is known as the genotype

Question 2

How is differential gene expression tightly regulated in terms of time?

Answer 2

Development like embryos versus adults

In response to hormones, infection and other signals

Question 3

How is differential gene expression tightly regulated in terms of space?

Answer 3

Different tissues or cell types express different genes

Question 4

What can the failure to regulate gene expression tightly lead to?

Answer 4

○ Metabolic diseases
○ Metastasis
○ Congenital disorders

Cancers

Question 5

What genes regulate development of anatomical structure?

Answer 5

Homeotic genes

Question 6

What gene is involved in the development of the head and thorax?

Answer 6

Drosophila melanogaster gene

Question 7

What can a mutation in the drosophila melanogaster gene cause?

Answer 7

Mutation in this gene can cause the fruit fly to have a bithorax or antennapedia

Question 8

What can totipotent stem cells do?

Answer 8

Differentiate into any type of cell

Question 9

What can pluripotent stem calls do?

Answer 9

Differentiate into any type of cell including committed stem cells like blood stem cells apart from placental cells

Question 10

What can skin cells for example do?

Answer 10

Can be reprogrammed back to pluripotent cells

Question 11

What is B-thalassaemia caused by?

Answer 11

Caused by insufficient expression of b-globin

Question 12

What is common in most cases of b-thalassaemia?

Answer 12

The b-globin protein is structurally normal

Question 13

What sites are included in the b-globin gene mutations?

Answer 13

Base change to TATA box which results in the prevention of the binding of RNA polymerase

Alteration of bases at intron-exon boundary prevents spliceosome from recognising the boundary

Question 14

Translational control in early embryogenesis:

What genes are expressed?

Answer 14

No genes expressed in first 4-8 cell divisions

Question 15

Translational control in early embryogenesis:

What happens once blastocyst is formed?

Answer 15

First genes to be expressed are die to up-regulation from maternally derived pre formed mRNA’s

Question 16

What other factors contribute to translational control?

Answer 16

Environmental stress

Question 17

What role does the 5’UTR play?

Answer 17

The 5’ UTR plays a major role in determining how effectively the ribosomes initiate translation

Question 18

How effectively does globin and ferritin translate?

Answer 18

Globin - v effectively

Ferritin - v ineffectively

Question 19

What role does the 3’UTR play?

Answer 19

The 3’ UTR plays a role in determining the stability of the mRNA

Question 20

What does the 3’UTR confer?

Answer 20

Confers stability of mRNA

Question 21

Why is 3’UTR in immune stress hormones important?

Answer 21

For stability as the mRNAs of immune stress hormones are very unstable

Question 22

Where does translation in eukaryotes start?

Answer 22

Starts from first AUG next to a Kozak sequence

Question 23

What does Ferritin do?

Answer 23

Binds Iron and retains in the cytoplasm as a store of excess

Question 24

When is Ferritin needed?

Answer 24

Needed at times of Iron excess

Question 25

What happens when there is a starvation of Fe?

Answer 25

Fe starvation inhibitor binds to the Ferritin mRNA preventing the ribosome from translating therefore prevents the formation of Ferritin

Question 26

What happens when there is an excess of Fe?

Answer 26

○ Fe binds to the Fe starvation inhibitor, preventing the inhibitor from binding to the Ferritin mRNA

This allows the ribosome to translate the Ferritin mRNA and allows the formation of the Ferritin.

Question 27

What are miRNA’s?

Answer 27

Short non-coding RNAs that regulate gene expression post transcription.

Question 28

How are miRNA’s synthesised?

Answer 28

○ Produced from precursor miRNA which is processed and exported to the cytoplasm.
○ The double stranded fragments are incorporated into RISCs
○ One strand is discarded leaving a single stranded miRNA
miRNAs base pair with specific mRNAs at there 3 UTR region reducing there stability and their translation into proteins.