What is the enzyme that attaches to the end of the template strand and extends the template strand?

• A. Telomerase
• B. DNA ligase
• C. Helicase
• D. Primase

Answer: (A)

Telomerase is the enzyme that attaches to the end of the template strand and extends it. It carries its own RNA template and uses reverse transcription to add telomeric repeats to the 3' end of the chromosome. This extension provides a new primer site for DNA polymerase to fill in the complementary strand, helping to prevent loss of genetic information at chromosome ends after each replication.

Other enzymes do different jobs: DNA ligase seals nicks after fragments are synthesized, helicase unwinds the double helix, and primase synthesizes RNA primers to start DNA synthesis. Telomerase specifically targets and lengthens chromosome ends, which is why it’s the correct answer here.