Question

List the proteins that unwind DNA during in vivo DNA synthesis. How do they function?

Short answer

Question: List the proteins that unwind DNA during in vivo DNA synthesis and briefly describe their functions. Answer: The primary proteins involved in unwinding DNA during in vivo DNA synthesis are Helicase, Topoisomerase, and Single-strand binding proteins (SSB). Helicase unwinds the DNA by separating the two strands, Topoisomerase resolves issues caused by overwinding, and SSBs stabilize the single-stranded DNA, ensuring that the replication machinery can access and copy the genetic information.

Step-by-step solution

Identify the primary proteins involved in unwinding DNA

In in vivo DNA synthesis, the proteins that are primarily responsible for unwinding the DNA molecule are Helicase, Topoisomerase, and Single-strand binding proteins (SSB).

Understanding the function of Helicase

Helicase is an enzyme that plays a key role in DNA replication by separating the two strands of the double helix. Its primary function is to use ATP to break the hydrogen bonds between the two nucleotide strands, thereby leading to the unwinding of the DNA molecule. Helicase moves along the DNA in a 5' to 3' direction, creating a replication fork.

Understanding the function of Topoisomerase

Topoisomerase is an enzyme that helps to manage the supercoiling or overwinding that occurs during the DNA unwinding process. The DNA ahead of the replication fork tends to become overwound, or supercoiled, due to the activity of helicase. Topoisomerase resolves this problem by cutting one or both DNA strands and allowing them to rotate around each other, thereby relieving the tension caused by overwinding. After this, Topoisomerase reseals the DNA strands, allowing the unwinding process to continue smoothly.

Understanding the function of Single-strand binding proteins (SSB)

Single-strand binding proteins (SSBs) are small proteins that bind to the separated single-strands of DNA after they are unwound by helicase. They play an essential role in stabilizing the single-stranded DNA and preventing them from reforming the double helix structure, thus allowing the replication machinery to successfully access and copy the genetic information on each strand.

Summary

During in vivo DNA synthesis, the proteins responsible for unwinding the DNA molecule are Helicase, Topoisomerase, and Single-strand binding proteins (SSB). Helicase unwinds the DNA by separating the two strands, Topoisomerase resolves issues caused by overwinding, and SSBs stabilize the single-stranded DNA, ensuring that the replication machinery can access and copy the genetic information.