Question

• Telomerase –

o Describe how a telomere (DNA double helix) is synthesized during replication. Be sure to mention all of the enzymes involved in this process.

o What role do telomere duplex DNA-binding proteins and telomere repeat binding factors (TRF proteins) in the formation of the final structure of the telomere? o What type of DNA polymerase is telomerase?

Answer 1

Telomere is the protective structure at each end of a eukaryotic chromosome and telomerase is an enzyme that catalyzes the lengthening of telomeres.The ends of the linear chromosomes are known as telomeres: repetitive sequences that code for no particular gene. These telomeres protect the important genes from being deleted as cells divide and as DNA strands shorten during replication.

In humans, a six base pair sequence, TTAGGG, is repeated 100 to 1000 times. After each round of DNA replication, some telomeric sequences are lost at the 5′ end of the newly synthesized strand on each daughter DNA, but because these are noncoding sequences, their loss does not adversely affect the cell. However, even these sequences are not unlimited. After sufficient rounds of replication, all the telomeric repeats are lost, and the DNA risks losing coding sequences with subsequent rounds.