Which part of the strand still needs to be replicated after the information-carrying DNA is replicated?

Which part of the strand still needs to be replicated after the information-carrying DNA is replicated?

• A. Centromere
• B. Promoter
• C. Telomere
• D. Gene

Answer: (C)

The main idea here is the end replication problem in linear chromosomes. When DNA is copied, the machinery can duplicate the information-carrying regions, but the extreme ends of the chromosomes—the telomeres—pose a challenge. Telomeres are repetitive, noncoding sequences at the ends that protect important genes. Because DNA polymerase cannot fully replicate the very end of a linear strand after primer removal, a small portion at the end isn’t copied in each round of replication. Over time this would shorten the chromosome, unless telomerase extends the telomeres in certain cells. Other parts like the centromere, promoter, or a gene are replicated along with the rest of the genome and don’t constitute the unfinished end.

The main idea here is the end replication problem in linear chromosomes. When DNA is copied, the machinery can duplicate the information-carrying regions, but the extreme ends of the chromosomes—the telomeres—pose a challenge. Telomeres are repetitive, noncoding sequences at the ends that protect important genes. Because DNA polymerase cannot fully replicate the very end of a linear strand after primer removal, a small portion at the end isn’t copied in each round of replication. Over time this would shorten the chromosome, unless telomerase extends the telomeres in certain cells. Other parts like the centromere, promoter, or a gene are replicated along with the rest of the genome and don’t constitute the unfinished end.