2. Definition:
In molecular biology, DNA replication is the biological
process of producing two identical replicas of DNA from
one original DNA molecule.
this process occurs in all living organisms and is the basis
for biological inheritance.
DNA replication occurs during the S-phase in interphase.
3. DNA STRUCTURE:
double stranded
nucleotides in DNA
contain a deoxyribose
sugar, a phosphate,
and nucleobase.
purines – A, G
pyrimidines – T, C
4. Replication as a Process:
DNA replication, like biological polymerization
processes, proceed in three enzymatically
catalyzed and co-ordinated steps as follows
1. Initiation
2. Elongation
3. Termination
5. Step 1: Initiation
helicase unwinding DNA
forming a “replication fork”.
multiple replication forks
a long a DNA molecule
create replication bubbles.
6. Step 2: Elongation
DNA polymerase uses each strand a template in the 3prime
to 5prime direction to build a complementary strand in the
5prime to 3prime direction.
7. Step 3: Termination
A different type of DNA polymerase removes the RNA
primer and replaces it with DNA.
DNA ligase joins the two okazaki fragment with phospodiester
bonds to produce a continues chain, each new DNA molecule is
removed by helicase.
each molecule is identical.
