DNA replication is the process by which a parent DNA molecule makes two identical daughter DNA molecules. It is semi-conservative, meaning the parent DNA strands separate and each serves as a template for a new complementary daughter strand. Meselson and Stahl's experiment provided evidence for this semi-conservative model of replication. They grew E. coli in medium containing a heavy isotope of nitrogen, then switched to light nitrogen medium. After multiple generations, they found DNA bands corresponding to hybrid heavy-light DNA strands, supporting the semi-conservative model. DNA replication requires dNTPs, DNA polymerase and other enzymes, primers, and separation of the parental strands by helicase.

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