MCAT Question A Day - 5/15/14 - Answer!

A tRNA molecule attaches to histidine. The anticodon on the tRNA is 5' -AUG-3 '. Which of the following nucleotide sequences in an mRNA molecule might contain the codon for histidine?

A. 3'-GCUAGGCCU-5'

B. 3'-GGTACCTAC-5'

C. 5'-CATTCTTAC-3'

D. 5'-UCAUGGAUC-3'

D is correct. The complementary sequence to 5'-AUG-3' is 5'-CAU-3'. Only D contains this sequence in any order. Remember, thymine is only found in DNA, not RNA so Band C must be wrong.

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