Question

What enzymatic features of DNA polymerase prevent it from replicating one of the DNA strands at the ends of linear chromosomes? Compared with DNA polymerase, how is telomerase different in its ability to synthesize a DNA strand? What does telomerase use as its template for the synthesis of a DNA strand? What does telomerase use as its template for the synthesis of a DNA strand? How does the use of this template result in a telomere sequence that is tandemly repetitive?

Answer 1

DNA polymerase cannot replicate one of the DNA strands at the ends of linear chromosomes. Telomerase is different from DNA polymerase in its ability to synthesize a DNA strand because it uses an RNA template and attaches to the end of the chromosome. Telomerase uses its own RNA template for the synthesis of a DNA strand, resulting in a tandemly repetitive telomere sequence.

Step-by-step explanation:

The ends of linear chromosomes, known as telomeres, present a problem for DNA polymerase because it can only add nucleotides in one direction. The lagging strand at the ends of chromosomes does not have a place for a primer to be made, preventing replication. To solve this problem, the enzyme telomerase attaches to the end of the chromosome and adds complementary bases to an RNA template, elongating the DNA strand. Telomerase uses its own RNA template as a guide for synthesizing the DNA strand, resulting in a telomere sequence that is tandemly repetitive.