LABORATORY REVIEW
MOLECULAR BIOLOGY
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Question
[CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
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a sequence of RNA
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a protein
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an enzyme
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the last thing to be transcribed
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Detailed explanation-1: -What is a start codon? The start codon is the initial set of codons in an mRNA transcript that is translated by a ribosome. In eukaryotes, the most common start codon is AUG which codes for methionine. The non-AUG start codons are rare in eukaryotes.
Detailed explanation-2: -The start codon is the first codon of a messenger RNA (mRNA) transcript translated by a ribosome. The start codon always codes for methionine in eukaryotes and Archaea and a N-formylmethionine (fMet) in bacteria, mitochondria and plastids.
Detailed explanation-3: -Asn, Asp, Cys, Gln, Glu, His, Lys, Phe, and Tyr have two codons; Ile has three codons; Ala, Gly, Pro, Thr, and Val have four codons; and Arg, Leu, and Ser have six codons. Only two amino acids-Met and Trp – are encoded by a single codon each.
Detailed explanation-4: -Each three-letter sequence of mRNA nucleotides corresponds to a specific amino acid, or to a stop codon. UGA, UAA, and UAG are stop codons. AUG is the codon for methionine, and is also the start codon.