introduction to gene expression

Question 1

what is the genetic blueprint in humans?

Answer 1

genotype

Question 2

Differential gene expression is tightly regulated in time:

Answer 2

Development like embryos versus adults

In response to hormones, infection and other signals

Question 3

Differential gene expression is tightly regulated in space:

Answer 3

Different tissues or cell types express different genes

Question 4

Failure to regulate gene expression tightly may lead to:

Answer 4

Metabolic diseases

Metastasis 

Congenital disorders 

Cancers

Question 5

Drosophila homeotic mutants

Answer 5

Homeotic genes regulate the development of anatomical structure

The drosophila melanogaster gene is involved in the development of the head and thorax  

A mutation at this gene can cause the fruit fly to have a bithorax or antennapedia

Question 6

totipotent stem cells can differentiate into

Answer 6

any type of cell

Question 7

pluripotent stem cells can differentiate into

Answer 7

any type of cell apart from placental cells then differentiate into committed stem cells for example blood stem cells

Question 8

what can be reprogrammed back into pluripotent cells?

Answer 8

some stem cells such as skin cells can be reprogrammed back

Question 9

β-thalassaemia

Answer 9

Caused by insufficient expression of β-globin

In most cases of β-thalassaemia, the β-globin protein is structurally normal 

There are multiple independently arising forms of the disease 

Mutations causing β-thalassaemia map to multiple sites in the β-globin: 

These include base changes to the TATA box which will prevent the binding of RNA polymerase and therefore inhibit transcription 

Spliceosome is unable to recognize the intron exon boundary due to the alteration to bases

Question 10

Post transcriptional gene regulation (Translational control)

Answer 10

Early embryogenesis:

No gene expression in first 4-8 cell divisions 

Once the blastocyst is formed, the first genes to be expressed are due to up-regulation from maternally derived pre formed mRNAs 

Environmental stress 

Ferritin

Question 11

Post transcriptional gene regulation (mRNAs)

Answer 11

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

Globin – very effectively translated 

Ferritin – very ineffectively translated 

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

Globin 3’ UTRs confer stability 

Immune stress hormones are very unstable mRNAs

Question 12

Ferritin

Answer 12

Fe starvation:

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

Fe excess: 

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 13

miRNA

Answer 13

Short non-coding RNAs that regulate gene expression post transcription

Synthesis of miRNA: 

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 pairs with specific mRNAs at there 3 UTR region reducing there stability and their translation into proteins