Describe the bonds that "un-zip" during the replication of dna.
During the replication of DNA, the bonds that "un-zip" are known as hydrogen bonds. These bonds are relatively weak and occur between the nitrogenous bases on the two DNA strands. The two types of nitrogenous bases involved in the hydrogen bonding are adenine (A) and thymine (T), which form two hydrogen bonds between them, and guanine (G) and cytosine (C), which form three hydrogen bonds between them.
To understand how these bonds "un-zip" during DNA replication, let's first look at the structure of DNA. DNA is made up of two complementary strands that are twisted together to form a double helix. Each strand consists of a sugar-phosphate backbone, with the nitrogenous bases attached to the sugar molecule.
During DNA replication, an enzyme called helicase unwinds and separates the two DNA strands, breaking the hydrogen bonds between the nitrogenous bases. Helicase moves along the DNA molecule, breaking the hydrogen bonds and separating the strands in a process known as strand separation or "unzipping."
Once the strands are separated, the exposed nitrogenous bases on each strand act as templates for the synthesis of new DNA strands. Free-floating nucleotides in the cell's nucleus are attracted to the exposed bases through a process called base pairing. Adenine (A) pairs with thymine (T) using two hydrogen bonds, while guanine (G) pairs with cytosine (C) using three hydrogen bonds.
DNA replication occurs simultaneously on both separated strands in opposite directions, a process known as semi-conservative replication. Enzymes called DNA polymerases then facilitate the formation of new phosphodiester bonds between the nucleotides, linking them together and creating new complementary strands.
In summary, the hydrogen bonds between the nitrogenous bases in DNA "un-zip" during replication, allowing the separation of the two DNA strands. This separation enables the new synthesis of complementary strands using base pairing and the formation of new phosphodiester bonds.