7a.DNA Replication

DNA Replication

Replication of DNA is required in mitosis to pass on exactly the same genetic information to the daughter cell.

For replication to occur the nucleus requires: • DNA (to act as a template) • A supply of free DNA nucleotides • The appropriate enzymes • A supply of ATP for energy

Semi-conservative replication DNA replication results in the formation of two new DNA molecules, each containing one strand from the parent molecule:

Replication of DNA is, therefore, said to be semi-conservative

Animations http://ncc.gmu.edu/dna/repa nim.htm http://www.bioteach.ubc.ca/T eachingResources/Molecul arBiology/DNAReplication. swf

• 1. Original DNA molecule unwinds • Free nucleotides find their complementary nucleotide on the exposed chain • Strong sugar-phosphate bonds form between nucleotides, giving the new strand a “backbone” • Weak hydrogen bond between two bases breaks, causing the two strands to separate (“unzip”) and expose the bases • Weak hydrogen bonds form between the new and exposed bases

NB: The enzyme that joins the nucleotides together to form the sugar-phosphate backbone is called DNA polymerase