What term refers to the repetitive DNA at chromosome ends that protect genetic information during cell division?

What term refers to the repetitive DNA at chromosome ends that protect genetic information during cell division?

• A. DNA polymerase III
• B. Amino acid
• C. rRNA
• D. Telomere

Answer: (D)

The concept being tested is the protective cap at the ends of linear chromosomes that shields genetic information during replication. This cap is called a telomere, and in humans it consists of repetitive DNA sequences (such as TTAGGG) that buffer the ends from degradation and from being mistaken for breaks. Telomeres solve the end-replication problem: when DNA is copied, the very end cannot be fully replicated, so some sequence is lost with each division. Telomeres absorb this loss so essential genes remain intact. Over time, telomeres shorten in most somatic cells, acting like a cellular clock, while certain cells (and some cancers) maintain or lengthen them with the help of telomerase. Other options don’t fit because they refer to non-end structures or molecules: a DNA polymerase III is an enzyme that copies DNA, amino acids are protein building blocks, and rRNA is a component of ribosomes involved in protein synthesis. None of these describe the protective repetitive DNA at chromosome ends.

The concept being tested is the protective cap at the ends of linear chromosomes that shields genetic information during replication. This cap is called a telomere, and in humans it consists of repetitive DNA sequences (such as TTAGGG) that buffer the ends from degradation and from being mistaken for breaks.

Telomeres solve the end-replication problem: when DNA is copied, the very end cannot be fully replicated, so some sequence is lost with each division. Telomeres absorb this loss so essential genes remain intact. Over time, telomeres shorten in most somatic cells, acting like a cellular clock, while certain cells (and some cancers) maintain or lengthen them with the help of telomerase.

Other options don’t fit because they refer to non-end structures or molecules: a DNA polymerase III is an enzyme that copies DNA, amino acids are protein building blocks, and rRNA is a component of ribosomes involved in protein synthesis. None of these describe the protective repetitive DNA at chromosome ends.