Which of the following statements is TRUE regarding DNA replication?

a) Only the lagging strand gets shortened during replication.

b) Both strands get shortened at the same end during replication.

c) Both strands get shortened at opposite ends during replication.

d) Only the leading strand gets shortened during replication.

e) Only the lagging strand gets shortened after every other round of replication.

Both strands get shortened at opposite ends during replication.

The answer is; B

During a replication round, the replication does not occur to the complete end of the chromosome. This is due to the physical challenge posed to the DNA polymerase in the replication of the lagging strand. Therefore, even the leading strand at the same end will not have complementary nucleotides to bind with. This overhang end is thus nicked. This is now the ends of chromosomes shorten with each round of replication. To avoid mutations, as a result, the end of chromosomes are extended with telomeres. These telomeres shorten with each replication round and protect the genes at the ends of chromosomes.

Ans.

During DNA replication, double stranded parent DNA converts into two template for synthesis of two new daughter strands, one leading strand and one lagging strand.

At the end of DNA replication, RNA primers are removed from the very ends of both the leading and lagging strand. Due to this, at 5' ends both daughter strands get shortened since there is no 3'-OH group to extend these stands.

Thus, the correct answer is option 'b). both strands get shortened at the same end during replication.'