Question

A single-strand binding protein (SSB) is required to ___ the separated strands

___ ____ is the 3'-5'helicase.

The combination of helicase, SSB, and Protein A separates a ϕX174 duplex into:
a single-stranded ___ and
a single-stranded ___ ____

Answer 1

A single-strand binding protein (SSB) is essential to stabilize single-stranded DNA during replication, preventing the strands from re-annealing. Helicase unwinds the DNA, SSBs bind to the strands, and topoisomerase reduces supercoiling tension, enabling the replication of DNA, including the formation of Okazaki fragments on the lagging strand.

Step-by-step explanation:

A single-strand binding protein (SSB) is required to stabilize the separated strands of DNA during replication to prevent them from re-annealing or forming secondary structures. Helicase unwinds the DNA at the origin of replication, and then SSBs bind to the now-single-stranded DNA. When working together with the helicase and a hypothetical protein A, the complex separates a φX174 duplex into a single-stranded DNA and a single-stranded complementary DNA.

1. DNA unwinds at the origin of replication.
2. Helicase opens up the DNA, forming replication forks.
3. SSBs coat the single-stranded DNA around the replication fork to prevent rewinding.
4. Topoisomerase relieves tension ahead of the replication fork by breaking and reforming the phosphate backbone of the DNA.
5. Primase synthesizes an RNA primer for DNA polymerase to start synthesizing the daughter strands.

Overall, this coordinated action results in DNA replication where one strand is continuous (leading strand) and the other (lagging strand) is synthesized in short segments, known as Okazaki fragments, which are later joined to form a continuous strand.