The mechanism of DNA replication gives rise to the “end-replication problem” for
ID: 151113 • Letter: T
Question
The mechanism of DNA replication gives rise to the “end-replication problem” for linear chromosomes. Over time, this problem leads to loss of DNA from the ends of chromosomes. In cells such as yeast, loss of nucleotides during replication is balanced by addition of nucleotides by telomerase. In humans, however, telomerase is turned off in most somatic cells early in development, so that chromosomes become shorter with increasing rounds of replication. Consider one round of replication in a human somatic cell. Which one of the following statements correctly describes the status of the two daughter chromosomes relative to the parent chromosome?
One daughter chromosome will be shorter at one end; the other daughter chromosome will be normal at both ends.
One daughter chromosome will be shorter at both ends; the other daughter chromosome will be normal at both ends.
One daughter chromosome will be shorter at both ends; the other daughter chromosome will be shorter at only one end.
Both daughter chromosomes will be shorter at one end, which is the same end in the two chromosomes.
Both daughter chromosomes will be shorter at one end, which is the opposite end in the two chromosomes.
Both daughter chromosomes will be shorter at both ends.
Explanation / Answer
Answer : Both daughter chromosomes will be shorter at one end, which is the opposite end in the two chromosomes. Here ends will be opposite in both the chromosomes but polarity will be same. And it will be 3' end. It means both the daughter chromosome strands will be shorter at 3' end but at opposite ends.