Gene organisation and transcription II Flashcards Preview

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Flashcards in Gene organisation and transcription II Deck (7)
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1
Q

What is mRNA processing?

A

Splicing out introns before it exits the nucleus and enters the cytoplasm

2
Q

What bases do introns begin with and end with?

A

GU —-AG

3
Q

Describe how small ribonuclear proteins (snRNPs) bind to the mRNA.

A

U1 binds to the splice donor site, U5 binds to the splice acceptor site, U2, U4 and U6 bind in the middle of the intron

4
Q

Describe how the intron is removed from the mRNA strand.

A

The RNA cleaves at the splice donor site and the first G loops round and forms a phosphodiester bond with an adenine residue in the middle of the intron (branchpoint). The mRNA then cleaves at the splice acceptor site and the intron is removed as a lariat structure.

5
Q

What two structures are added during post-translational modification and why?

A

7-methylguanylate cap – protects the RNA from degradation – enhances translation
Poly-A-tail – occurs 11-30 bases downstream of an AAUAAA sequence in the mRNA – also acts as protection – added one base at a time

6
Q

Give an example of a disease that affects one of the structures added during post-translational modification.

A

Poliomyelitis affects 7-methylguanylate cap recognition during translation

7
Q

Give an example of a mutation in a splice site which features in human disease.

A

Beta Thalassemia – splice site mutation in the beta globin gene – caused by imbalances in the relative amounts of alpha and beta chains