DNA replication is the process by which DNA makes a copy of itself during cell division. There are three models of DNA replication: semiconservative, conservative, and dispersive. In semiconservative replication, the two parental DNA strands separate and each acts as a template to make a new complementary strand, resulting in two double-stranded daughter molecules each with one original and one new strand. The steps of replication involve unwinding the DNA double helix, forming a replication fork, and synthesizing new strands in the 5' to 3' direction along the leading and lagging strands through the use of primers, DNA polymerase, and DNA ligase.

1. DNA REPLICATION
BY
IQRA AYUB
MS BIOTECH

2. AIM
• To know how the DNA replicates

3. CONTENTS
• INTRODUCTION
• MODELS OF DNA REPLICATION
• STEPS OF DNA REPLICATION
• CONCLUSION

4. DNA
• Stands for: Deoxyribonucleic acid
• Long thin molecule made up of nucleotides
• Deoxyribose( a sugar)
• Phosphate group
• Nitrogen-containing base (ATGC)
Adenine
Guanine
Cytosine
Thymine

6. MODELS OF DNA REPLICATION
SEMI CONSERVATIVE
• Two parental strands separate
• Each makes a copy of itself
• After one round of replication, the two daughter molecules each
comprises one old and one new strand

8. CONSERVATIVE MODEL OF REPLICATION
• Two parental DNA strands are back together after replication has
occurred
• One daughter molecule contains both parental DNA strands
• Other daughter molecule contains DNA strands of all newly-
synthesized material.

10. DISPERSIVE MODEL OF REPLICATION
• Two parental strands is distributed more
or less randomly between two daughter molecules.

11. DNA REPLICATION
• Process by which DNA makes a copy of itself during cell division.
• Semiconservative
• each strand in the DNA double helix acts as a template for the
synthesis of a new, complementary strand

14. STEPS
• Unzip double helix structure
• Enzyme helicase breaks the hydrogen bond
• Separation of the two single strands of DNA creates a ‘Y’ shape called
a replication ‘fork’.
• The two separated strands will act as templates for making the new
strands of DNA.

15. • LEADING STRAND:
• 3’ to 5’ direction
• Towards the replication fork
• LAGGING STRAND:
• 5’ to 3’ direction
• Away from the replication fork

16. LEADING STRAND
LAGGING STRAND
REPLICATION FORK

17. LEADING STRAND
• Primer binds to the end of
leading strand
• Act as starting point of DNA
synthesis
• DNA polymerase binds to the
leading strand
• Adding
new complementary nucleotide
bases (A, C, G and T) to the
strand of DNA in the 5’ to 3’
direction.
• Called as continuous replication
LAGGING STRAND
• RNA primers binds at various
points along the lagging strand
• Chunks of DNA, called Okazaki
fragments, are then added to
the lagging strand also in the 5’
to 3’ direction
• Called discontinuous replication
• DNA ligase seals up the
sequence of DNA into two
continuous double strands.

19. CONCLUSION
The discoveries of DNA structure and function aid us in understanding
how cellular processes take place but also provide us with many tools
to exploit in the laboratory