DNA Replication Challenges and Mechanisms

The video explains the challenges of replicating linear chromosomes, focusing on the lagging strand's synthesis and the end replication problem. DNA polymerases require a free 3' hydroxyl group, which RNA primers provide at intervals. However, the lagging strand cannot be fully replicated, leading to chromosome shortening. Telomerase, an enzyme with an RNA template, extends the parental strand, allowing complete replication by DNA polymerase Alpha.

What unique problem do linear chromosomes face during DNA replication?

• They replicate faster than circular chromosomes.

• They require a free three prime hydroxy group for elongation.

• They cannot replicate at all.

• They do not need any enzymes for replication.

How does the replication machinery build the lagging strand?

• By a back stitching mechanism using RNA primers.

• By starting from the end of the chromosome.

• By continuous elongation in the five prime to three prime direction.

• By using only DNA polymerase.

Why does the lagging strand stop short of the chromosome end?

• Because the leading strand blocks it.

• Because there is no three prime hydroxy group available.

• Because the final RNA primer cannot be removed.

• Because it runs out of nucleotides.

What happens to chromosomes if the end replication problem is not solved?

• They become longer with each replication cycle.

• They remain unchanged.

• They progressively shorten during each replication cycle.

• They duplicate uncontrollably.

What enzyme solves the end replication problem?

• DNA polymerase

• RNA primase

• Telomerase

• Helicase

What type of sequence do the ends of chromosomes contain?

• C-rich sequences

• Random sequences

• A-T rich sequences

• G-rich series of repeats

How does telomerase function in elongating the parental strand?

• By cutting the DNA strand.

• By using an RNA template within the enzyme.

• By binding to the leading strand.

• By removing RNA primers.

Which enzyme completes the lagging strand after telomerase action?

• DNA polymerase Alpha

• Ligase

• RNA polymerase

• Helicase

What is the role of DNA polymerase Alpha in lagging strand completion?

• It cuts the DNA strand.

• It binds to the leading strand.

• It carries a DNA primase as one of its subunits.

• It removes RNA primers.

What ensures the complete copying of chromosome ends in new DNA?

• Continuous elongation of the leading strand.

• The action of telomerase and DNA polymerase Alpha.

• The presence of multiple RNA primers.

• The absence of any enzymes.