Fundtest 3 Post-Transcriptional Regulation Of Gene Expression Ii

Front 1

What happens in constitutive splicing?

Back 1

Every intron is removed and every exon is incorporated into the mature RNA. This makes a single form of mature mRNA from the primary transcript.

Front 2

What are the 3 mechanisms that can give rise to multiple forms of mature RNA transcripts?

Back 2

1. Using different promoters

2. Selection of different polyadenylylation sites

3. Alternative splicing of primary transcript.

4. Or a combination of these 3.

Front 3

What is the difference between constitutive and combinatorial exons?

Back 3

constitutive exons must be incorporated into the final RNA transcript while the combinatorial may be included or excluded, allowing for a variety of isoforms

Front 4

Why do you need such a variety of RNA transcripts?

Back 4

So that you can expand the coding potential of a genome.

Front 5

What must be true for an RNA to be able to exit into the cytosol?

Back 5

It should contain a 5’ capped structure, a poly A tail, and all introns removed.

Front 6

How does the RNA exit the nucleus?

Back 6

It enters the cytosol 5’ first. Its 5’ end is recognized by a cap binding protein and its poly A tail is recognized by a poly A binding protein. Some of the proteins associated with it are exchanged.

Front 7

What are the possible fates of mRNA in the cytoplasm?

Back 7

Translation, degradation, localization->translation.

Front 8

Is mRNA more stable in prokaryotes or eukaryotes?

Back 8

Eukaryotes are more stable on average and therefore have a longer half-life.

Front 9

Why is it important for RNA to be relatively unstable?

Back 9

Because in order to have a quick response to an environmental change, you will need to change out the RNA quickly to adapt.

Front 10

True/False: The rates of mRNA translation do not have an effect on mRNA degradation.

Back 10

False: inhibited translation will increase degradation because they are in competition with each other.

Front 11

How does mRNA translation inhibit degradation?

Back 11

When mRNA is being translated, it is circularized and the poly-A end where it would be degraded is protected by the proteins.

Front 12

What are the 2 mechanisms of eukaryotic mRNA decay?

Back 12

General decay pathway (for moth mRNAs) and specific sequences (only for certain mRNAs)

Front 13

How does general decay pathway for mRNA work?

Back 13

The poly-A tail is removed first and exposes the 3’ end that is then quickly degraded from 3’ to 5’.

Front 14

How does specific sequence degradation of mRNA work?

Back 14

These mRNAs will contain a specific sequence somewhere in the middle of the RNA that will be the site for endonucleolytic cleavage. This site is usually protected, but once it is not, it will be cleaved in 2 and the 2 pieces will degrade the same way as in the general pathway.

Front 15

What is RNA editing?

Back 15

It is another way to increase diversity of genetic information and is the process that changes one or more nucleotides in an RNA transcript by deaminating a base, either A to I or C to U.

Front 16

What are the 3 ways RNA editing can increase protein diversity?

Back 16

1. Altering aa coding possibilities, 2. Introducing a premature stop codon. 3. Changing splice site in a transcript.

Front 17

How is RNA edited from A to I?

Back 17

The protein ADAR (adenosine deaminase acting on RNA) recoginezes a dsRNA region that occurs between an exon and an intron before they are cleaved.

Front 18

How is apolipoprotein B mRNA edited from C to U?

Back 18

An editosome acts on the single-stranded regions of the transcripts. This is often tissue specific (this is in the liver)

Front 19

What are the stages of gene expression?

Back 19

Transcription, transcript processing, mRNA export, and translation.

Front 20

True/False: Each of the steps of gene expression happen one at a time through to completion before the next one begins.

Back 20

False.

Front 21

Capping, RNA splicing, 3’ end formation and polyadenylation, and nuclear export are all coupled to what?

Back 21

Transcriptional machinery.

Front 22

Why is post-transcriptional regulation important?

Back 22

It is important for controlling the level of gene expression in addition to transcriptional control.

Front 23

Why is capping and methylation important?

Back 23

It is important for mRNA export, protection, and translation.

Front 24

Why is splicing important?

Back 24

It increases gene coding potential through alternative splicing.

Front 25

Why is 3’ polyadenylation important?

Back 25

It is important for mRNA protection and translation.

Front 26

Why is mRNA export important?

Back 26

It is for mRNA quality control. Incorrectly processed mRNAs are retained and degraded in the nucleus.

Front 27

Why is mRNA degradation important?

Back 27

It is important for controlling the level of gene expression.

Front 28

Why is RNA editing important?

Back 28

It can also increase gene coding potential by altering amino acid codon and splice site, introducing sometimes, a premature stop codon.

Front 29

Post-transcriptional regulation of gene expression acts on a pre-mRNA: 1. Before the pre-mRNA is synthesized. 2. After the synthesis of pre-mRNA is completed. 3. As soon as the synthesis of the pre-mRNA is initated.

Back 29

3. As soon as the synthesis of the pre-mRNA is initiated.

Front 30

True/False: Alternative splicing can serve as a useful mechanism for increasing the coding capacity of the genome.

Back 30

True.

Front 31

True/False: Messenger RNAs (mRNAs) constitute the majority of total cellular RNAs.

Back 31

False. rRNA comprises the majority of RNA.

Front 32

mRNAs are modified in: 1. Eukaryotic cells. 2. Prokaryotic cells.

Back 32

1. Eukaryotic cells.

Front 33

Which feature is not found in a mature mRNA? 1. Capped G, 2. Poly A tail. 3. Intron. 4. Exon.

Back 33

3. Intron.

Front 34

What are 3 ways to increase coding capacity?

Back 34

Alternative splicing, using different promoters, and using a different poly adenylation site.

Front 35

Are poly A tails found in DNA?

Back 35

No.

Front 36

Pre-mRNA splicing requires: 1. snRNAs. 2. Proteins. 3. snRNAs and proteins (splicesome)

Back 36

3. snRNAs and proteins (splicesome)

Front 37

Which of the following can result in multiple mRNAs (transcripts) from a single gene? 1. Use of different promoters. 2. Selection of different polyadenylylation sites. 3. Alternative splicing. 4. All of the above.

Back 37

4. All of these above.