Summary DNA replication using the Watson and Crick Model

DNA replication using the Wat
and Crick DNA model, includin
nucleotide composition, pairin
bonding
DNA Replication is the production of two identical double-stranded molecul
one original double-helix molecule.

DNA replicates during interphase prior to mitosis, and each cell receives on
the coded instructions

DNA polymerase binds to nucleotides to form a new strand

Helicase a type of enzyme that unwinds parental bonds
Primase a type of enzyme that adds a short primer to the template strand

Leading strand nucleotides that are added in the same direction as the replication fork
Lagging strand the other strand where nucleotides are added in chunks 'Okazaki frag

Ligase joins Okazaki fragments and seals in the sugar-phosphate backbone



Why is DNA replication a complex process?

DNA has to be unwound from its spiral configuration before the strands

Chemical and physical reactions take place simultaneously by enzymes

The two strands of DNA run in opposite directions (antiparallel) and the
only be added in one direction (onto the free 3' end)

DNA replication errors may occur and therefore may need to be correct



STEP 1 IN DNA REPLICATION - The DNA double helix unwin