GENETICS AND EVOLUTION
MOLECULAR BASIS OF INHERITANCE
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Question
[CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
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UAA, UAG and UGA
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GUA, GUG, GCA, GCG and GAA
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UUC, UUG, CCU, CAA and CUG
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UUA, UUG, CUU, CUC and CUG
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Detailed explanation-1: -UUA, UUG, CUU, CUC and CUG are degenerate codons as they all code for the same amino acid Leucine.
Detailed explanation-2: -The codons UAA, UAG, and UGA are the stop codons that signal the termination of translation. Figure 2 shows the 64 codon combinations and the amino acids or stop signals they specify.
Detailed explanation-3: -As well known, the genetic code is degenerate mainly at the third codon position, for example GGN, GCN and GUN, 4 codons each, code for Gly, Ala and Val, respectively (Figure 1).
Detailed explanation-4: -So the correct option is ‘UGG’.
Detailed explanation-5: -UAA, UAG and UGA are the stop codons, and do not code for amino acids. They are also known as termination codons or nonsense codons, and act as signals on the mRNA to stop protein synthesis.