1. Deoxyribonucleic Acid
DNA
Deoxyribonucleic Acid

2. Lesson Objectives At the end of this lesson you should be able to
Outline the simple structure of DNA
Name the four bases and the base pairs in DNA
Distinguish between coding and non coding structures
Define triplet base code
Outline the structure of RNA
Name the bases in RNA
Discuss the replication of DNA

3. What is DNA Hereditary material
Carries and passes on genetic information
It is a nucleic acid
Made up of nucleotides

4. The DNA Double Helix Two parallel strands
Each with a series of bases to the inside
The bases are directly opposite each other
The bases link each other in pairs
These links form the steps of the ladder

5. The DNA Double Helix Hydrogen bond- link Parallel Strand
Base
Base

6. The Bases
Adenine (A)
Thymine (T)
Cytosine (C)
Guanine (G)

7. The Base Pair Rule
The bases can occur in any sequence along a strand of DNA
But the sequence must be complimentary to the sequence on the other strand

8. The Base Pair Rule Adenine can only join to Thymine A T
Guanine can only join to Cytosine
G C

9. Building DNA

10. Building DNA

11. Learning Check What does DNA stand for? Name the four bases in DNA
Which base complements Adenine?
Which base compliments Guanine?

12. Non Coding DNA Only about 3% of DNA is composed of genes
97% of DNA is non coding DNA or junk DNA

13. Coding DNA
The parts of DNA that contain information to make RNA or protein
Coding DNA in genes are called exons

14. Non Coding DNA
Do not contain critical information for the production of protein
They are now thought to play a role in gene expression
Non coding DNA within genes is called introns

15. Learning Check
Label a gene and a piece of non coding DNA in the following picture

16. RNA
Ribonucleic Acid Operates with DNA to make proteins Has Uracil instead of Thymine

17. Differences between DNA and RNA
Double strand
Sugar is deoxyribose
Has Thymine
Much longer
Self replicating
Only in the nucleus
RNA
Single strand
Sugar is ribose
Has Uracil
Short molecule
Not self replicating
Found in nucleus and cytoplasm

18. Similarities between DNA and RNA
Both are nucleic acids
Both contain
adenine, guanine and cytosine nucleotides
Operate together to produce specific proteins

19. Learning Check What does RNA stand for?
What three bases do DNA and RNA have in common?
What base does RNA have instead of Thymine?
Where do you find both DNA and RNA?
Where else will you find RNA?

20. Nucleic Acid Structure
Higher Level
Nucleic Acid Structure

21. Nucleotides
Nucleotides are carbon ring structures containing nitrogen linked to a 5-carbon sugar (a ribose)
5-carbon sugar is either a ribose or a deoxy-ribose
In eukaryotic cells nucleic acids are either:
Deoxyribose nucleic acids (DNA
Ribose nucleic acids (RNA)

22. Base H+ Sugar A Nucleotide P O OH HO NH2 N - OH O CH2 H OH Phosphate2’ 3’ 4’ 5’ 1’ OH

23. Coding and Non Coding Parts
Non coding Structures
Sugar – Phosphate
Coding Structures
Base Sequences

24. Purine Bases Adenine and Guanine Double ringed molecular structures
Known as Purine Bases

25. Pyramidine Bases Thymine and Cytosine single ringed structures
Known as Pyramidine bases

26. Purines Pyrimidines Uracil CH3 N O NH Thymine N Adenine NH2 NH2 O N NH
(RNA)
CH3 N O NH
Thymine
(DNA) N
Adenine
NH2
NH2 O N NH
Guanine N O
NH2
Cytosine

27. Base Numbers
Number of Purine Bases = Number of Pyramidine Bases This led to the discovery of Base Pairing

28. Base Pairing Guanine And CytosineH O N
Guanine - N O H
Cytosine + + - - +
Three Hydrogen Bonds

29. Base Pairing Adenine And Thymine- +
Adenine
CH3 N O H + -
Thymine
Two Hydrogen Bonds

30. Base Pairing Guanine And Thymine
CH3 N O H + -
Thymine H O N
Guanine + -

31. D N A B A S E S SUGAR-PHOSPHATE BACKBONE 3’Hydroxyl group
5’Phosphate group
SUGAR-PHOSPHATE BACKBONE H P O HO
CH2 OH
NH2 N NH
B A S E S O H P HO
CH2
H2N N HN H OH P O HO
CH2
CH3 HN N
H2O
D N A H P HO O
CH2 N
H2N
H2O
3’Hydroxyl group
5’Phosphate
group

32. The Watson - Crick Model Of DNA
T A
G C
C G
G C
T A
3.4 nm
1 nm
Minor
groove
The Watson - Crick Model Of DNA
Major
groove
0.34 nm

33. What have you learned Can you ………………
Outline the simple structure of DNA
Name the four bases and the base pairs in DNA
Distinguish between coding and non coding structures
Define triplet base code
Outline the structure of RNA
Name the bases in RNA
Discuss the replication of DNA

34. End