GEN BIO 2 | DNA Replication

DNA Replication

• Also known as the semi-conservative replication, it is the process of making an identical copy of a DNA molecule to pass the genetic trait,

• The new DNA has one parent strand and one daughter strand.

• DNA elongates and slants in the 5’ to 3’ manner only.

DNA Replication as Semi-discontinuous

• The leading strand is synthesized continuously (5’ to 3’).

• The lagging strand is produced discontinuously in short stretches called Okazaki fragments.

Process of DNA Replication

1. The parental molecule has two complementary strands of DNA. Each base is paired by hydrogen bonding.

2. The two DNA strands are separated by the helicase enzyme to form a replication fork. Each strand is a template for a new complementary strand.

3. Single-strand binding proteins prevent the unwound strands from rejoining.

4. Topoisomerase untwists the double helix.

5. Primase makes a short stretch of RNA on the DNA template, called a primer

6. DNA Polymerase will add nucleotides complementary to the bases of the parental strand to form the new backbone of the strand. This replaces the RNA primer

7. The leading strand synthesizes continuously.

8. The lagging strand will synthesize discontinuously.

9. Exonuclease removes the RNA primer as the DNA Polymerase replaces it with the DNA strand

10. Ligase seals the sugar phosphate backbone, forming the phosphodiester bonds.

Helicase

an enzyme that separate the strands using hydrogen bonds

Single-strand binding proteins

They prevent the unwound strands from rejoining with one another.

Topoisomerase

it untwists the double helix

Primase

makes a short RNA primers on the DNA template to serve as guides as nucleotides will only attach to an existing strands

DNA Polymerase

adds DNA nucleotides to the RNA primer; only adds from the 5’ end to the 3’ end

Ligase

seals the sugar-phosphate backbone

Exonuclease

removes the RNA primer

Synthesis of Lagging Strand

Primase and DNA Polymerase take turns creating the RNA primer for one strand and creating the new DNA for it