Gene Expression PT2

Question 1

Can transcription and translation happen at the same time in Pro vs Euk?

Answer 1

Can happen at same time in pro but not in euk

Question 2

When are intron sequences removed?

Answer 2

During splicing - introns are transcribed but not translated

Question 3

What is splicing?

Answer 3

The process that involves the removal of introns and linkage of extrons

Question 4

What is the splicesome?

Answer 4

The complex of snRNPs (small nuclear RNA and protein) that precisely removes introns from pre-RNA

Question 5

What does the intron RNA have to show its an intron?

Answer 5

Particular sequence within and at the intron-extron boundaries
5’ splice site (GU) , branch site and 3’ splice site (AG)

Question 6

Which is the donor site on in intron?

Answer 6

-GU site

Question 7

Which is the acceptor site on the intron?

Answer 7

-AG site

Question 8

What happens non-coding eukaryotic RNAs?

Answer 8

Non-coding eukaryotic RNAs are processed (trimmed, chemically modified) from larger precursor RNAs to mature, functional RNAs
-Trimmed not spliced

Question 9

What is RNA capping?

Answer 9

Involves the covalent attachment of a modified guanosine to the 5’ end of the mRNA

Question 10

When does RNA capping occur?

Answer 10

Occurs while transcription occurs after the first 20-25nt have been transcribed

Question 11

What is the function of RNA capping?

Answer 11

-Prevents degradation from 5’ end by nucleases
-Allows proper exiting of mRNA from nucleus to cytoplasm
-Cap structure enables ribosome binding to mRNA

Question 12

Where is the polyA tail attached?

Answer 12

At the 3’ end of most mature mRNA and consists of 100-300 adenine residues

Question 13

What is the prupose of the polyA tail?

Answer 13

Leads to mRNA stability in cytosol - gives mRNA longer in cell, would be broken down quite easily without
-may also occur in bacteria reason unknown