DNA replication enzymes

Important enzymes of DNA replication

Stage	Enzyme	Function
Initiation	DNA Helicase SS binding protein DNA gyrase primase	Unwinds the DNA Protects the DNA single strand from binding by hydrogen bonds Relieves tensions Adds RNA primers to initiate elongation
Elongation	DNA polymerase Ⅲ	DNA polymerase Ⅲ adds complementary nucleotides in the 5’ to 3’ direction.
Termination	DNA polymerase Ⅰ DNA ligase	Removes RNA primers by deoxyribonucleotides. Joins the Okazaki fragments together creating phosphodiester bond.

Chromosome

Chromatid

1-       eukaryotic chromosome

2-       Centromere - the point where the two chromatids touch

3-       Short arm

4-       Long arm

Chromatin: is the combination of DNA and other proteins that make up the contents of the nucleus.

Centriole:

Centrosome: are composed of two orthogonally arranged centrioles surrounded by an amorphous mass of protein termed the pericentriolar material.