DNA polymerases are unable to replicate which areas of the chromosome?

• A. Introns
• B. Telomeres
• C. Centromeres
• D. Exons

Answer: (B)

Verified step by step guidance

1. Understand the structure of a chromosome: Chromosomes have specific regions such as telomeres, centromeres, exons, and introns. Each of these regions has distinct functions and characteristics.
2. Recognize the role of DNA polymerases: DNA polymerases are enzymes responsible for synthesizing new DNA strands by adding nucleotides to a pre-existing chain during DNA replication.
3. Identify the challenge with telomeres: Telomeres are repetitive nucleotide sequences at the ends of chromosomes. They protect the chromosome from deterioration but pose a challenge for DNA polymerases because these enzymes cannot fully replicate the very end of the linear DNA strand.
4. Understand the end-replication problem: During DNA replication, the lagging strand synthesis leaves a small portion of the telomere unreplicated. This is because DNA polymerases require a primer to initiate synthesis, and once the primer is removed, there is no upstream DNA to extend from.
5. Learn about the role of telomerase: To address the replication issue at telomeres, cells use an enzyme called telomerase, which extends the telomeres, allowing for complete replication of chromosome ends. This enzyme is not active in most somatic cells, leading to gradual telomere shortening with each cell division.