22)The closest eukaryotic equivalent of the Shine Delgarno sequence is the a) 60

Question

22)The closest eukaryotic equivalent of the Shine Delgarno sequence is the a) 60S large ribosomal subunit b) 40S small ribosomal subunit c) 5' cap region d) polyA tail e) introns 23) In which stage of translation is GTP not used a) initiation b) elongation c) translocation d) termination e) none of the above 24) Specificity in translation is achieved by all of the following except a) using specific tRNA synthetases for each amino acid b) using an anticodon c) using a degenerate triplet code having codons for each amino acid d) using different RNA polymerases

Explanation / Answer

22)The closest eukaryotic equivalent of the Shine Dalgarno sequence is the

ANSWER IS:

c) 5' cap region

EXPLANATION:
Shine-Dalgarno sequence in prokaryotes is sequence where ribosome lands. In Eukaryotes, ribosome bind at 5'cap at the end of the mRNA.

Cap complements the function of shine-dalgarno sequence in the eukaryotes which is ribosome recruitment.

23) In which stage of translation is GTP not used

ANSWER IS:

e) none of the above

EXPLANATION:

Steps of initiation.

- GTP-eIF2 + Met-tRNA complex bind with 40s and form 43s preinitiation complex.

- GTP bound to eIF2 will be hydrolized to GDP-eIF2 + P. and release of eIF3 & eIF1A

For initiation phase we use : 1 GTP

For elongation: 2 GTP is used

For termination: 1 GTP is used


24) Specificity in translation is achieved by all of the following except

ANSWER IS:
c) using a degenerate triplet code having codons for each amino acid

EXPLANATION:

Specificity in the translation depends on bonding of the anticodon to the codon and attachment of amino acids to tRNAs.

The genetic code is degenerate as different codons specify the same amino acid which means amino acids may each be encoded by more than one codon.


25) In an unprocessed newly synthesized eukaryotic protein which is true:

ANSWER IS :

e) a and c

EXPLANATION :

mRNA codons are read from 5' to 3' , and they specify the order of amino acids in a protein from N-terminus (methionine) to C-terminus. The last amino acid is always encoded stop codon.

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