A mature mRNA has a total of 900 nucleotides (from the 5\' to the 3\' ends) righ

Question

A mature mRNA has a total of 900 nucleotides (from the 5' to the 3' ends) right before leaving the nucleus. The resulting polypeptide will have:

A. 900 amino acids

B. 300 amino acids

C. less than 300 amino acids

D. More than 300 but less than 900 amino acids

Initiation of translation:

A. is triggered by a TATA box

B. occurs when a 5' cap sequence at the 5' end of the template strand is identified.

C. occurs when the ribosome attaches to the 5' cap sequence at the 5' end of the mRNA

D. is triggered by one or more transcription factors

E. Occurs when the ribosome reaches the AUG next to the ribosomal binding site on the mRNA

F. is triggered by the attachment of a snRNP molecule to the start codon

Explanation / Answer

1. As the mRNA has 900 nucleotides then the number of amino acids it will produce will be less than 300.

Because one amino acid has 3 nucleotides hence total of 300 amino acids should be produced but remember that there will be a stop codon and will not produce any aminoacid and also in some species the start codon also not form any amino aicd . There fore total number of amino acids formed will be less than 300.

2. Initiation of translation

E. E. Occurs when the ribosome reaches the AUG next to the ribosonal binding site on the mRNA.

There is an initiation complex which contains

Ribosome

mRNA

tRNA

These three come together in just the right way and forms a complex and recognises the AUG on the mRNA sequence which is the start codon and codes for methionine and from there tranlation starts.

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