Question:
What is the enzyme by which cancer cells become immortalised?
What is the enzyme by which cancer cells become immortalised?
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Telomerase rebuilds shortened telomeres, letting cancer cells bypass the normal division limit.
Updated On: Jul 8, 2026
- DNA polymerase
- mRNA polymerase
- Telomerase
- Topoisomerase
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The Correct Option is C
Solution and Explanation
Step 1: Understand why normal cells cannot divide forever.
Each time a normal somatic cell divides, the DNA replication machinery cannot fully copy the very end of the chromosome. The telomere, a repetitive protective cap at the chromosome end, shortens with every division. Once telomeres become too short, the cell stops dividing and enters senescence.
Step 2: Learn what telomerase does.
Telomerase is a ribonucleoprotein enzyme that carries its own RNA template and adds fresh repeat sequences back onto the shortened telomere ends. This rebuilds the telomere after each division.
Step 3: Apply this to cancer cells.
Most cancer cells switch telomerase back on, a process that is normally silent in adult somatic cells. Active telomerase keeps telomeres from shortening, so the cancer cell escapes senescence and can divide an unlimited number of times. This unlimited replicative capacity is called immortalisation, and it is one of the hallmarks of cancer.
Step 4: Rule out the other enzymes.
DNA polymerase copies the DNA strand during replication but cannot solve the end replication problem on its own. mRNA polymerase (RNA polymerase) makes messenger RNA from a DNA template and has no role in telomere length. Topoisomerase relieves the twisting strain in DNA during replication and transcription but does not add telomeric repeats.
Final Answer:
The enzyme that lets cancer cells become immortal by maintaining telomere length is telomerase. \[ \boxed{\text{Telomerase}} \]
Each time a normal somatic cell divides, the DNA replication machinery cannot fully copy the very end of the chromosome. The telomere, a repetitive protective cap at the chromosome end, shortens with every division. Once telomeres become too short, the cell stops dividing and enters senescence.
Step 2: Learn what telomerase does.
Telomerase is a ribonucleoprotein enzyme that carries its own RNA template and adds fresh repeat sequences back onto the shortened telomere ends. This rebuilds the telomere after each division.
Step 3: Apply this to cancer cells.
Most cancer cells switch telomerase back on, a process that is normally silent in adult somatic cells. Active telomerase keeps telomeres from shortening, so the cancer cell escapes senescence and can divide an unlimited number of times. This unlimited replicative capacity is called immortalisation, and it is one of the hallmarks of cancer.
Step 4: Rule out the other enzymes.
DNA polymerase copies the DNA strand during replication but cannot solve the end replication problem on its own. mRNA polymerase (RNA polymerase) makes messenger RNA from a DNA template and has no role in telomere length. Topoisomerase relieves the twisting strain in DNA during replication and transcription but does not add telomeric repeats.
Final Answer:
The enzyme that lets cancer cells become immortal by maintaining telomere length is telomerase. \[ \boxed{\text{Telomerase}} \]
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