What enzyme forms covalent bonds between restriction fragments?

When it comes to the functions of enzyme, what enzyme forms covalent bonds between restriction fragments? We colllected this biology as a MCAT practice test.

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What enzyme forms covalent bonds between restriction fragments?

DNA ligases

DNA ligases are important enzymes in living organisms, and the reactions they catalyze play an important role in the replication and repair of DNA.

There are two major groups of DNA ligases:

One group is the ATP-dependent DNA ligases that use the energy of ATP to catalyze the formation of phosphodiester bonds between two nucleotide chains.

The other group is the NAD*-dependent DNA ligases that use the energy of nicotinamide adenine dinucleotide (NAD+) to catalyze the formation of phosphodiester bonds between two nucleotide chains.

DNA ligases, also known as DNA binders, play a special and critical role in molecular biology by linking the 3′-OH end of one base of a DNA strand to the 5′-P end of its neighboring base. DNA Ligase causes the two to form a phosphodiester bond, thus linking the two adjacent bases. The catalytic action of ligase requires the consumption of ATP.

Whether double or single-stranded, DNA ligase can link the 3′ end of DNA to the 5′ end of DNA by forming a phosphate ester bond.

Although there are other proteins in the cell. For example, DNA polymerase, in which one strand of DNA is used as a template, binds DNA by forming a phosphodiester bond (DNA ligase sews DNA fragments together) through a polymerization reaction in which a single strand of DNA on the other side is broken off. The phosphodiester bond between the two nucleotides cut by the restriction enzyme is restored.

However, the DNA polymerase bonding process is only an incidental function of the polymerization reaction. The real work of the DNA adhesion reaction in the cell is performed by the DNA binders.

The function of DNA binders is to bind broken DNA. Only the DNA replication and DNA repair reactions in the cell involve the synthesis of broken DNA. Therefore, DNA mucolytic enzymes play an important role in both of these mechanisms.

In addition to intracellular adhesion reactions, almost all molecular biology laboratories use DNA binders to perform recombinant DNA experiments. Perhaps this can also be classified as another important function.

Dependent DNA polymerase

dependent DNA polymerase, DNA pol, is a class of enzymes that uses parental DNA as a template to catalyze the polymerization of substrate dNTP molecules to form daughter DNA.

The discovery of DNA polymerase I (pol I) is of great importance to the study of biology because it plays a central role in life processes and has enabled us to understand how DNA is formed.

Because it plays a central role in the life process, it has enabled us to understand how DNA is replicated and repaired. Before a cell divides, pol I copies all the components of the cell’s DNA. The mother cell then passes a copy of its DNA to each daughter cell, thus passing on genetic information from generation to generation.

What is the difference between DNA ligase and DNA polymerase?

1. Different formation methods

DNA ligases form phosphodiester bonds between two DNA fragments, not between a single nucleotide and a DNA fragment. And DNA ligases cannot catalyze the joining of two free DNA strands.

DNA polymerases can only add a single nucleotide to an existing DNA fragment to form a phosphodiester bond.

The DNA polymerase acts as a catalyst, catalyzing the replication of the original DNA. The original DNA and the replicated DNA are then paired with a template and joined together to form a new DNA strand.

2. Template is different

DNA ligase does not require a template. Because DNA ligase is to connect two gaps in the DNA double-strand at the same time. DNA ligase is used to join DNA fragments with complementary sticky ends or T4DNA ligase is used to join DNA fragments with flat ends directly.

The structure of DNA polymerase is adenosine triphosphate.

3. Different application areas

DNA ligase is mainly used for genetic engineering. It is also called “gene stitching” because it reassembles the sticky ends “cut” by restriction endonucleases.

For example, in genetic engineering, E. coli ligase connects sticky ends and T4 ligase connects both sticky ends and flat ends.

DNA polymerase plays a role in DNA replication, mainly by connecting DNA fragments to individual deoxyribonucleotides in the phosphodiester bond.

Correct Answer

Here is the correct answer to What enzyme forms covalent bonds between restriction fragments?

DNA ligase forms covalent bonds between restriction fragments.

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