9:34 nccu.blackboard.com 30 Q. 1 What are aminoacyl -RNA synthetase and transcri

Question

9:34 nccu.blackboard.com 30 Q. 1 What are aminoacyl -RNA synthetase and transcription factors? (Mention their functions) Q. 2. What are the specific role (function) of A, P and E site on ribosomes for tRNA? Q. 3 How many ATP and GTP is required during translation to form a 6 amino acid long peptide ? Give steps (Hints look at the amino acid activation and peptide formation slides) Q. 4. If the DNA coding strand sequence is is the following ACAGTCGATGGGCTGC a. What is template strand sequence? b. What is pre-mRNA transcript sequence Q. 5. What are promoter and transcription factors? Q. 6. RNA Sequences remaining after splicing are A. Introns B. Exons C. Splice variant

Explanation / Answer

Question: 1

What are amino acyl tRNA synthetase and transcription factors?

Aminoacyl tRNA synthetase:

Aminoacyl tRNA synthetase is the enzyme that helps tRNA carry its aminoacid from the aminoacid pool. tRNA has a triplet codon in its anticodon arm based on which it carries the specific aminoacid. Anticodon arm is complementary to the mRNA.

There are about 20 different aminocyl tRNA synthetase each specific for one type of aminoacid.

Transcription factors:

Transcription factors are proteins that help to transcribe DNA to RNA.

Question: 2

What are specific role of A, P and E site on ribosomes for tRNA?

A, P and E site are present on the ribosomes that are attached with the mRNA.

Question: 3

How many ATP and GTP is required during translation to form a 6 amino acid long peptide? Give steps.

Energy cost of Translation:

Activation of aminoacyl tRNA – 2ATP

Initiation of translation – 1 GTP

Ribosomes to move along mRNA – 1 GTP

tRNA to Exit from E site – 1 GTP

Termination – 1 GTP

Energy cost for 6 aminoacids:

Activation of aminoacyl tRNA – 12 ATP

Initiation – 1 GTP

Ribosomes to move along mRNA – 5 GTP

tRNA to Exit from E site – 5 GTP

Termination – 1 GTP

For 6 aminoacids to be translated 12 ATPs and 12 GTPs are needed.

Question: 4

If the DNA coding strand sequence is the following:

ACAGTCGATGGGCTGC

a. What is template strand sequence?

Coding strand:

The strand which has the sequence that directly corresponds to mRNA is called the coding strand.

Template strand:

The strand whose sequence is copied to synthesise the mRNA is the template strand.

Answer:

Template strand sequence:

TGTCAGCTACCCGACG

b. What is pre mRNA transcript sequence?

The mRNA that is produced after transcription is called as the pre mRNA transcript or precursor mRNA because it has to undergo post transcription modification that is 5’ methylation, 3’ poly Adenylation and splicing. After these process the mature mRNA is generated.

Question: 5

What are promoter and transcription factors?

Promoter are the sequence present on the DNA that initiate the transcription. It is present near the transcription start site in the 5’ end.

The RNA pol.ymerase, transcription factors, activators and repressors bind to the promoter region to regulate the transcription.

Question: 6

RNA sequences remaining after splicing are

Splicing is the technique by which all introns – non coding regions are removed and Exons - coding regions are joined to form the mature mRNA that is translated into protein.

Answer: b. Exons

After splicing, the RNA sequences will only have Exons – coding region that is translated into protein.

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