DNA Repair Mechanisms and Processes

The video explains how cells repair double strand breaks in DNA using homology-dependent repair. It begins with the degradation of DNA to form single-stranded tails, followed by strand invasion and D-loop formation. DNA synthesis occurs, creating a replication bubble that translocates across the template strand. The process concludes with the formation of heteroduplex DNA and the filling of remaining gaps. An alternative repair method, non-homologous end joining, is briefly introduced.

What is the initial sequence of the parental DNA duplex in the repair process?

• XYZ ABC

• XYZ DEF

• CDE FG

• AB CDE

What happens to the DNA during the initial repair steps?

• It undergoes nuclea degradation to form single-stranded tails.

• It immediately forms a displacement loop.

• It is completely repaired without any degradation.

• It forms a bubble without any degradation.

What is the role of the single-stranded tail in the repair process?

• It invades a homologous duplex to form a heteroduplex.

• It forms a loop with the homologous duplex.

• It degrades further to form a bubble.

• It remains inactive during the repair process.

What is formed when the gray single strand invades the pink duplex?

• A replication fork

• A displacement loop

• A double helix

• A single-stranded loop

What initiates DNA synthesis in the repair process?

• The end of the pink duplex

• The 5' end of the invading strand

• The 3' end of the invading strand

• The middle of the invading strand

What is the role of the DNA synthesis bubble?

• It forms a permanent structure in the DNA.

• It translocates across the template strand.

• It remains stationary during the repair.

• It degrades the template strand.

What happens to the newly synthesized strand after the bubble dissociates?

• It is degraded.

• It remains inactive.

• It is captured by the single-stranded tail from the other side of the break.

• It forms a new bubble.

What serves as a primer for new DNA replication across the break?

• The end of the pink duplex

• The middle of the broken duplex

• The 3' hydroxy end of the broken duplex

• The 5' end of the broken duplex

What is the final outcome of the repair process?

• The DNA forms a new loop.

• The DNA is repaired with the original sequence.

• The DNA is repaired with a new sequence.

• The DNA remains broken.

What is the template for the new DNA synthesis in the repair process?

• A non-homologous duplex

• A homologous duplex

• A single-stranded DNA

• A random DNA sequence