Sex Chromosomes

How does DNA replicate itself and in what direction?

DNA replicates via semi-conservative replication, where each strand serves as a template. DNA is synthesized in the 5' → 3' direction.

What is the origin of replication?

A specific sequence where replication begins; proteins bind here to open the double helix.

What is the role of DNA polymerase?

DNA polymerase adds nucleotides to the 3' end, synthesizing DNA in the 5' → 3' direction and proofreading for errors.

What is the role of helicase?

Helicase unwinds and separates the DNA strands at the replication fork.

What does topoisomerase (gyrase) do?

It relieves twisting tension ahead of the replication fork by cutting and rejoining DNA strands.

What is the function of primase?

Primase synthesizes short RNA primers to provide starting points for DNA polymerase.

What do single-stranded binding proteins (SSBs) do?

SSBs stabilize separated DNA strands and prevent them from re-annealing or forming secondary structures.

What is the role of ligase?

Ligase joins Okazaki fragments on the lagging strand, creating a continuous DNA strand.

What is the step-by-step process of DNA replication and the role of each enzyme/protein?

1. Origin of replication: replication begins. 2. Helicase: unwinds DNA. 3. Topoisomerase: relieves supercoiling. 4. SSBs: stabilize strands. 5. Primase: makes RNA primers. 6. DNA polymerase: synthesizes DNA 5' → 3'. 7. Ligase: joins Okazaki fragments. Leading strand is continuous; lagging strand is fragmented.