Final answer:
Tandem repeat sequences at chromosome ends are known as telomeres. They are protected and maintained by the enzyme telomerase, which adds necessary repeats to preserve chromosome integrity during cell division. so, option 1 is the correct answer.
Step-by-step explanation:
Tandem repeat sequences found at the ends of chromosomes, such as TTAGGG as found in vertebrates, are known as telomeres. Telomeres consist of noncoding repetitive sequences that protect coding sequences from being lost as cells divide. In humans, the sequence TTAGGG is repeated 100 to 1000 times at the chromosome ends. The enzyme telomerase plays a crucial role in maintaining these telomere regions by adding the necessary repeats using its built-in RNA template, thereby ensuring the integrity of the chromosomes during cell division.
The ends of the linear chromosomes are known as telomeres, which have repetitive sequences that code for no particular gene. In humans, a six base pair sequence, TTAGGG, is repeated 100 to 1000 times. The discovery of the enzyme telomerase helped in the understanding of how chromosome ends are maintained. The telomerase enzyme contains a catalytic part and a built-in RNA template. It attaches to the end of the chromosome, and DNA nucleotides complementary to the RNA template are added on the 3' end of the DNA strand. Once the 3' end of the lagging strand template is sufficiently elongated, DNA polymerase can add the nucleotides complementary to the ends of the chromosomes. Thus, the ends of the chromosomes are replicated.