Question

Oxidative deamination of adenine produces hypoxanthine (the base of inosine), which can base pair with cytosine. (a) If no repair takes place, describe the makeup of the DNA in the two daughter cells following cell division. (b) Describe the makeup of the DNA in the four daughter cells following a second round of cell division.

Short answer

Answer

Step-by-step solution

DNA repair

In a typical mammalian cell, everyday DNA damage exceeds 100,000 molecular lesions. These metabolic and environmental-caused lesions must be repaired in order to maintain genomic integrity. These systems range from simple multienzyme ones that only reverse the chemical modification of nucleotide bases to more intricate ones that depend on the duplex DNA's inherent redundancy of information to repair the damaged molecule

Deamination of adenine

Adenine is converted into guanine-like hypoxanthine when it undergoes deamination in the presence of nitrous, where it forms two of guanine's three hydrogen bonds with cytosine.

(b) Makeup of DNA in the four daughter cells following a second round of cell division

Finally, cytosine is converted to uracil. As a result, DNA treated with nitrous acid undergoes conversions from A-T to G-C and vice versa. The base deamination reactions for nitrite, which is nitrous acid's conjugate base absent nitrous acid, also occur independently. Therefore, in the second round of cell division, have cells with transition mutation.