Final answer:
It is true that DNA repair enzymes preferentially recognize defects on newly synthesized DNA strands to correct errors such as those caused by deamination. Mechanisms like mismatch repair and base excision repair identify the new strand by markers such as the absence of methyl groups in bacteria, allowing specific repair of that strand.
Step-by-step explanation:
The statement in question is true: DNA repair enzymes do preferentially recognize defects on newly synthesized DNA strands. During DNA replication, the newly synthesized strand may contain incorrect nucleotides due to deamination or other sources of damage. The DNA repair mechanisms, such as mismatch repair and base excision repair, have evolved ways to discriminate the new strand from the old one in order to correct these errors.
For example, the mismatch repair system identifies the newly synthesized strand in bacteria such as E. coli by detecting the lack of methyl groups, which are only added to the parental strand after replication. This allows repair enzymes, like endonuclease, to excise and replace incorrect bases specifically on the new DNA strand, reducing the likelihood of permanent genetic mutations.
Additionally, damage like spontaneous deamination, where cytosine becomes uracil, is recognized by base excision repair mechanisms. DNA glycosylase enzymes identify and remove the incorrect uracil base, further ensuring genetic fidelity.