A 200 amino acid protein is encoded by a mature mRNA that is 800b long. Examination of this mRNA sequence and ORF analysis should reveal:
a. | Two major ORFs adding up to 600b |
b. | One major ORF 600b long |
c. | Many small ORFs corresponding to the exons |
d. | At least 4 ORFs adding up to 600b |
e. | One very large ORF nearly 800b long |
Answer: Option B is correct.
Explanation:
The genetic code is a triplet.
One amino acid is encoded by a three-nucleotide codon.
200 amino acids = 200 X 3 = 600 nucleotides.
But, the given mRNA is 800 nucleotides long. So, the remaining 200 nucleotides corresponding to 5'-UTR and 3'-UTR.
A single ORF codes for a single protein. It is given that the given mRNA codes for a single protein. So, it can not contain more than one ORF.
It is given that the size of mature mRNA is 800 ntd. Mature mRNA
contains all the exons joined together (introns are removed during
splicing).
It can not contain a single 800 ntd ORF as the protein is only 200 amino acids long.
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