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Wize University Biology Textbook > DNA Replication & Repair

Telomerase

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Telomerase

  • In the linear DNA of eukaryotic cells, RNA primers cannot be added to the 3' end of the DNA (lagging strand) in order to allow DNA polymerase to replicate the very end of the strand.
  • The enzyme telomerase extends the 3' end of the lagging strand by adding a DNA sequence to which a primer can attach. DNA polymerase III can now replicate the 3' end of the lagging strand.
  • Prokaryotic cells don't have this problem and therefore don't have telomerase because they have circular chromosomes and during replication both replication forks meet in the middle.

Photo by Fatma Uzbas / CC BY

Practice: Prokaryote Telomerase?

Why don't prokaryotic chromosomes require a telomerase during replication?

Practice: Absence of Telomerase

What would happen to a eukaryotic chromosome after repeated rounds of replication if the telomerase was not functioning properly?
Extra Practice
DNA Replication
Which of the following proteins can extend the 5' end of a DNA strand?
1. DNA polymerase III
2. Ligase
Practice: Meiosis (Telomeres)
A hedgehog has a diploid number of 48 chromosomes. How many telomeres would you find in a a hegdehog gamete at the beginning of telophase II?
Which of the following functions as an RNA-protein complex?
Ribosomes
snRNPs
DNA Replication
Which of the following proteins can extend the 5' end of a DNA strand?
1. DNA polymerase III
2. Ligase
Telomeres
A human cell as 23 pairs of chromosomes. What is the total number of telomeres found at prophase of mitosis?
If you block the activity of DNA polymerase III, which of the following would be affected?
The ends of chromosomes are elongated by telomerase. Which of the following proteins is also involved in ensuring the inheritance of sameness at the ends of chromosomes?
i. DNA polymerase III
ii. Primase
A cancer cell divides rapidly and never dies. Which of the following would explain the immortality of the cancer cell?
Which of the following would not be classified as a phosphodiesterase?
i. Primase
ii. Topoisomerase
A flowering plant has 20 pairs of chromosomes. How many telomeres would a gametophyte somatic cell have at prophase of mitosis?
From Term Test 2 Prep: What does the process of non-homologous end joining accomplish?
Which of the following statements is TRUE regarding telomeres?
They get shorter with each replication cycle in somatic cells
Their length is maintained in all cells by the enzyme telomerase