Question

In E. coli which containa temperature-sensitive mutant in the gene for dCTP deaminase, production of dTTP is decreased at restrictive temperature of 37 °C. Knowing what you do about replication in E. coli, what cellular outcomes do you expect when these bacteria are grown at 37 °C? (For the sake of this problem set assume that no alternative pathways for production of dTTP are utilized to circumvent the dCTP deaminase mutation.)

Answer 1

cCTP and dTTP play plays an essential role in DNA replication. dCTP deaminase hydrolyzes dCTP to dUTP.

At 37⁰C dCTP deaminase got mutated in temperature-sensitive mutant thus hydrolysis of dCTP decreases, due to which the effective concentration of dCTP increases in the cytosol.

Low dTTP and high dCTP causes following the physiological outcome=====

It decreases the genome stability as a mismatch in bases occurs due to the low or high concentration of dCTP and dTTP.

A decrease in the stability of genome increases the chance of higher mutation rates.

At high dCTP abnormal replication stop occurs in DNA replication fork that leads to increased S-Phase during replication that leads to increased generation time.