Sometimes, chemical damage to DNA can occur just before DNA replication begins, not giving the repair system enough time to correct the error before the DNA is duplicated. This gives rise to mutation. If the cytosine in the sequence TCAT is deaminated and not repaired, which of the following is the point mutation you would observe after this segment has undergone two rounds of DNA replication?
a. TTAT
b. TUAT
c. TGAT
d. TAAT

TTAT

Explanation:

Deamination is a reaction that causes mutations in DNA, with the release of ammonia. Deamination may convert cytosines into uracils. These mutations caused by deamination of cytosine are recognized by specific endonucleases that repair these modifications by replacement with cytosine

many other transport proteins, often called pumps, move materials against a concentration gradient. active transport drives molecules across a membrane from a region of lower concentration to a region of higher concentration. this process, shown in figure 5.1, uses transport proteins powered by chemi- cal energy.