Base-pair substitutions involving the third base of a condon are unlikely to result in an error in the polypeptide. This is because: (pick one)
a. substitutions are corrected before transcription begins.
b. substitutions are restricted to introns.
c. The base-pairing rules are less strict for the third base of codons and anticodons.
d. a signal-recognition particle correct coding errors.
e. transcribed errors attract snRNP's, which then stimulate splicing and correction.
This is an AP Biology question. The answer is "c" - The base-pairing rules are less strict for the third base of codons and anticodons. This is because of "The Wobble Hypothesis". Francis Crick hypothesized that the first two bases of the codon and the last two bases of the anticodon form A:U or G:C base pairs but pairing between the third base of the codon and the first base of the anticodon follows less strict rules. The advantage of these less strict rules or "wobble" is that if all three base pairs of the codon/anticodon were of the strong Watson Crick type then tRNAs would dissociate less quickly from mRNA which would slow protein synthesis. "Wobble" allows translation to proceed more efficiently.