Answer to Question #251759 in Microbiology for Pri

Question #251759

When looking at DNA replication what are the most important steps and enzymes used ?

Expert's answer

There are three process in DNA replication.

Initiation, elongation and termination.

1. First step in DNA replication is to separate the double helix of DNA. This is done by the enzyme helicase. Helicase breaks the hydrogen bond between opposite nitrogen bases.

2. The separation of the double helix of DNA will leads to the formatio of a replication fork which is 'Y' shaped. The separated strands act as a template for making complementary strands.

3. One strand in the replication fork have 3' to 5' polarity, is is called the leading strand. Other strand have 5' to 3' polarity which is the lagging strand. These two strands replicated differently.

4. A primer will come and attach to one end of the leading strand, primer is produced by primase enzyme. Primer is the starting point of DNA synthesis. DNA polymerase will add nucleotides complementary to the leading strand in 5' to 3' direction.

5. Numerous RNA primers will attach to different points in lagging strand. An okazaki fragment are added to the kagging strand in 5' to 3' direction. This kind of replication is discontinuous because the okazaki fragment should joined later.

6. Once the complementary bases are matched the exonuclease enzyme will remove the primer, these gaps are filled by other complementary nucleotides.

7. Finally the DNA ligase enzyme join the newly synthesized strands to the template and make a DNA double helix. As a result we will get two DNA having one new and one old strand.

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