1. DNA REPLICATION
Dr. Sandhya
Associate Prof. Botany

2. CONTENT

3. The process by which a parent DNA
molecule gives rise to 2 exactly similar
daughter DNA molecules

4. CHARACTERISTICS
Semi-conservative
Semi-discontinuous
Uni-/ Bidirectional

8. MESELSON & STAHL'S EXPERIMENT
 Cultured E. coli in medium containing a "heavy" isotope of nitrogen 15N
 When grown on medium containing heavy 15N the bacteria took up the
nitrogen and used it to synthesize new biological molecules, including DNA
 After many generations growing in the 15N medium, the nitrogenous bases
of the bacteria's DNA were all labeled with heavy 15N
 Then, the bacteria were switched to medium containing a "light" 14N
isotope and allowed to grow for several generations
 DNA made after the switch would have to be made up of14N

9.  Collected small samples in each generation and
extracted and purified the DNA
 They then measured the density of the DNA (15N
and 14N content) using density gradient
centrifugation
 This method separates molecules such as DNA
into bands by spinning them at high speeds

11. RESULT

13. REQUIREMENTS FOR DNA
REPLICATION
dNTPs
• dATP, dGTP, dTTP,
dCTP
Enzymes
• DNA polymerase
• Helicase
• Topoisomerase
• SSBPs
Primer
• Small RNA
molecule

14. MECHANISM OF DNA REPLICATION