Question

During translation in eukaryotes the anticodon to be aligned with the initiation codon is

• A. 5' UAC 3'
• B. 3' UAC 5'
• C. 5' UCA 3'
• D. 3' CAU 5'

Answer 1

Answer: (B)

3' UAC 5'

As we know that "AUG" is the most common start/initiation codon and its complementary tRNA has anticodon “UAC” which makes options C and D wrong. The mRNA codon is read in 5’ to 3’ direction. Alignment of the mRNA and tRNA is antiparallel which means that 5’ end of mRNA faces 3’ end of tRNA. The first base of the codon in mRNA (read in the 5’ to 3’direction) pairs with the third base of the anticodon thus the initiation codon 5’ AUG 3’ pairs with 3’ UAC 5’ anticodon. Thus, option B is correct. If the two RNAs would align parallel to each other, the initiation codon 5’ AUG 3’ would pair with 5’ UAC 3’ anticodon. Option A is incorrect.