Genetics - Analysis and Principles 3rd Edition by Robert Brooker

Exercise 4

The compound known as nitrous acid is a reactive chemical that replaces amino groups ( NH 2 ) with keto groups (=O). When nitrous acid reacts with the bases in DNA, it can change cytosine to uracil and change adenine to hypoxanthine. A DNA double helix has the following sequence:
TTGGATGCTGG
AACCTACGACC
A. What would be the sequence of this double helix immediately after reaction with nitrous acid Let the letter H represent hypo-xanthine and U represent uracil.
B. Let's suppose this DNA was reacted with nitrous acid. The nitrous acid was then removed, and the DNA was replicated for two generations. What would be the sequences of the DNA products after the DNA had replicated twice Your answer should contain the sequences of four double helices. Note: During DNA replication, uracil hydrogen bonds with adenine, and hypoxanthine hydrogen bonds with cytosine.