dna

1. DNA Structure & Replication
Patel krinal S
Environmental Science
Msc Sem.-I
Roll No.-313

2. Contents
 What is the DNA?
 DNA Structure
 DNA replication
 Types of replication

3. What is the DNA ?
 Found in almost all cells
 contained phosphorus in the form of
phosphate
 Double stranded molecule
 Double helix structure
 Made by nucleotide

4. DNA STRUCTURE

5. DNA STRUCTURE
• DNA has three main components:
1. Deoyribxose (a pentose sugar)
2. Nitrogen base
3. phosphate group

6. 1. Deoxyribose sugar
 Deoxyribose is a pentose monosacchride,
a pentose sugar has five carbon atoms.
• Deoxyribose found in DNA ,is a modified
sugar, lacking one oxygen atom .

7. 2. Nitrogen base
 They are divided into two groups
Pyrimidines and Purines
• Pyrimidines 1.Thymine
2. Cytosine
• Purines 1.Adenine
2.Guanine

8. 3.Phosphate group
 A deoxyribos-phosphate backbone joins
together nucleotides in a DNA sequence
 This backbone is composed of alternating
sugar and phosphate groups

9. Nucleosides & Nucleotide
 A nucleoside consist simply of a nitrogen
base and a five carbon sugar.
 A nucleotide is composed of a nitrogen
base ,a five carbon sugar and one or more
phosphate groups.

10. DNA Replication Steps
1. The separation of DNA strands
2. Replication fork formation
3. Binding of bases to each strand
4. The termination of replication process

12. DNA Replication
 Fundamental processes occurring in all cell for
transfer of genetic information to daughter cell.
 Each cell must replicate its DNA before division.
 DNA is copied during the S or synthesis phase of
interphase .
 New cells will need identical DNA strands.

13. Conti…
 Must carry the information.
 Cracking the genetic code.
 Extreme the DNA replication is necessary is order to
preserve the integrity of the genome in successive
generation.
 Start from ‘origin’.
 Can be uni or bidirectional.
 Involves DNA templating.
 RNA primers required.

14. 1.Conservative
2.Semi-conservative
3.Dispersive
There are three type of replication

15. Conservative
 The parental molecule
directs synthesis of an
entirely new double-
stranded molecule, such
that after one round
replication.
 Both parental strands stay
together after DNA

16. Semi-conservative
 It was proposed by Watson &
Crick.
 The parent DNA strand
separates into two
 Each strand serves as a
template for new
complementary strands.
 The new double helix is half
original.

17. Dispersive
 Parental & daughter DNA
are interspersed in both
strands following.
 Parental DNA breaks up into
small fragments which then
synthesize complementary
strands that is randomly.

18. • https:// www.google.co.in
• https:// www.slideshare.net/namrta chhabra
Guided By: Kajal Joshi
References