Question

You design a circular ssDNA with a labeled RNA primer (alpha-P^32 labeling). You add polymerase epsilon and required enzymes for replication to the fragment. What will you expect to see on autoradiography after gel electrophoresis?

(a) Single labeled band with some labeling at the bottom region

(b) Two labeled band one much lower than the other with labeling at the bottom region

(c) No band but labeling at the bottom

(d) Two labeled band one much lower than the other with no labeling at the bottom

This question was posed to me during an interview for a job.

The query is from DNA Replication Eukaryotes topic in division DNA Replication of Cytogenetics

Answer 1

Correct answer is (d) Two labeled band one much lower than the other with no labeling at the bottom

To explain: Alpha-P^32 incorporated the label in the entire RNA primer fragment. As polymerization will take place the 5’->3’ exonuclease activity of pol eta will produce labeled oligomers of that RNA. One band will correspond to unreplicated DNA, the lower one to oligomer. No labeled monomer is produced.