Molecular Genetics Practice Exam

Telomeres act as protective caps at chromosome ends and are shortened with each round of DNA replication due to the end-replication problem. Telomerase is a reverse transcriptase that carries its own RNA template and uses it to add telomeric repeats to the 3’ end of telomeres, effectively lengthening them. In most somatic cells, telomerase is not active, so each cell division leaves the telomeres a bit shorter. When telomeres become critically short, the cell detects DNA damage and halts division or undergoes programmed cell death, a process called replicative senescence. This limits the number of times somatic cells can divide and helps prevent genomic instability. The statement is correct because it accurately describes both the enzyme’s action—extending telomeres using its RNA template—and the typical somatic-cell situation—lack of telomerase leading to progressive telomere shortening and eventual senescence.