Over on the thread The Chemical Structure of Double-Stranded DNA we're having a little discussion about exam questions related to the structure of DNA and reading frames.
I thought it might be fun to post some multiple choice questions from old exams to see if the Sandwalk readers are as smart as my third year molecular biology students. Here's a question from 1999.
Examples of overlapping genes that are transcribed in opposite directions (i.e., opposite strands serve as templates) are very rare in biology. Part of the coding region from the middle of two such overlapping genes is shown below. In one of these genes a mutation results in the substitution of valine for methionine in the polypeptide (i.e., the normal protein has methionine). What effect would this have on the polypeptide sequence encoded by the other gene? (the sequence of the normal or wild-type gene is shown)
a) no change
b) substitution of methionine for arginine
c) premature termination (shorter protein)
d) substitution of threonine for isoleucine
e) substitution of serine for phenylalanine