Question

Telomeres are extremely repetitive. They consist of which sequence repeated over and over again?

(A) 5'GGTTAG3'
(B) 5'GTTTAA3'
(C) 5'GGGTTG3'
(D) 5'GCTAAG3'

Answer 1

Telomeres consist of the six-base-pair sequence TTAGGG, repeated extensively. The correct answer to the sequence that forms the telomere is (A) 5'GGTTAG3'. The enzyme telomerase maintains these sequences by adding nucleotides to the 3' end of the DNA strand.

Step-by-step explanation:

The telomeres are repetitive sequences at the ends of chromosomes that protect them during cell division. In humans, these sequences are comprised of the six-base-pair sequence TTAGGG, which is repeated between 100 to 1000 times. The correct answer to the student's question is (A) 5'GGTTAG3', which corresponds to one repeat of the human telomeric sequence, but written in the complementary and reverse orientation to reflect how it is read in terms of DNA synthesis.

The discovery of telomerase has provided insight into how telomeres are maintained to prevent the loss of genetic information. Telomerase, with its catalytic part and built-in RNA template, elongates the telomere by adding nucleotides to the 3' end of the DNA strand, compensating for the shortening that occurs during DNA replication.