1. DNA – The Molecule of Life
Hidden in all life is a unique code This code is in the form of a chemical, called DNA DeoxyriboNucleic Acid

2. WE STUDY DNA FOR MANY REASONS SUCH AS….
WHY DO WE STUDY DNA?
WHY IS IT IMPORTANT???????
WE STUDY DNA FOR MANY REASONS SUCH AS….
CENTRAL IMPORTANCE TO ALL LIFE ON EARTH
MEDICAL BENEFITS SUCH AS CURES FOR DISEASES OR RISKS FOR GENETIC DISEASES.

3. Where is DNA found in the cell?
One chromosomes
enlarged
Genes are pieces of DNA that code for a characteristic e.g. Eye colour
Chromosomes in the cell nucleus
Chromosome uncoiled to show DNA

4. DNA – The Molecule of Life A photo of DNA from an electron microscope
What does DNA look like?
A photo of DNA from an electron microscope

5. DNA – The Molecule of Life
What is DNA made up of ? What results if a DNA molecule like this is broken down?

6. DNA – The Molecule of Life
Watson and Crick discovered that DNA has 2 strands twisted together called a double helix. (like a twisted ladder)
DNA is found to be made of three types of molecules:

7. DNA – The Molecule of Life
Sugar
This is a special type of sugar called deoxyribose

8. DNA – The Molecule of Life
Phosphate

9. DNA – The Molecule of Life
Base
NITROGENOUS BASE

10. DNA – The Molecule of Life
SUMMARY: DNA is made of three types of molecules
1. Sugar
2. Phosphate
3. Nitrogenous Base

11. and a base joined to the side
A SINGLE NUCLEOTIDE
These three molecules are bonded in a special way to form the monomers of the DNA molecule called NUCLEOTIDES
Consists of a Sugar
and a base joined to the side
a Phosphate
joined to

12. In the DNA molecule, nucleotides link together to form long chains called polynucleotide chains. (poly=many)

13. There are four different bases. These make up the “steps of the ladder”
The sugar and phosphates are the same throughout the DNA molecule but …

14. The four bases are either single or doubled ringed
A single ringed base
A double ringed base

15. There are two types of single ringed bases (PYRIMIDINES)
Thymine C
Cytosine

16. There are two types of double ringed bases (PURINES)
Adenine G
Guanine

17. Four different nucleotides therefore occur in the DNA moleculeG

18. The polynucleotide chain now with the four different basesG

19. The DNA molecule consists of TWO chains
The sugar and phosphates form the backbone of DNA (the “side of the ladder”)
The DNA molecule consists of TWO chains

20. It is arranged in the opposite direction to the first chain
What do you notice about the second chain?
The 2 DNA strands are ANTIPARALLEL to each other

21. But how are the bases arranged to link the two chains?

22. always links to a one ringed base
When bases combine ..
A two ringed base
always links to a one ringed base

23. Adenine always joins to Thymine Guanine always joins to Cytosine
Chargaff’s Rule:
Adenine
Thymine
Adenine always joins to Thymine A T
Guanine
Cytosine
Guanine always joins to Cytosine G C

24. look at how the bases link with each other to join the two chains of the DNA molecule
Complimentary rule: DNA made of 2 strands of nucleotides bonded in a specific way C A G C T A T G

25. A The DNA molecule has many nucleotides To see this clearly we need to
simplify a nucleotide
Sugar
Base A
Phosphate

26. Which nucleotide will link to A ?
Try to determine which nucleotide will link to the form the second DNA chain G C A T C G T A T A A T G C
Which nucleotide will link to A ?
Remember
A joins to T and
G to C C G T A A T

27. Two Sugar-Phosphate backbones
As the bases link to each other, the DNA molecule is twisted into a double helix (looks like a twister ladder)
Inter-linking bases-
Two Sugar-Phosphate backbones

28. Genetic diversity
Different arrangements of NUCLEOTIDES in DNA provide the key to DIVERSITY among life: We all have different codes that make us unique!!!!

29. As soon as you walk in
5-10 minutes to finish DNA strand from Friday (supplies found on counter)
Make sure it is colored as instructed on whiteboard
Everyone needs their notebook – please get it

30. DNA
UNIT DNA Replication

31. DNA replication How DNA is copied

32. DNA Replication occurs during the S Phase of Interphase
DNA Replicates in the cell’s nucleus

33. DNA replication
When a cell divides, the DNA needs to be copied so that each new cell has the same DNA as the parent cell

34. DNA replication The two chains separate
Enzyme Helicase
Breaks the
Hydrogen
Bonds
New strands
form
complimentary
to parent strands
Called Semi-Conservative because each
New DNA has a strand from the parent
The two chains
separate

35. The 2 DNA strands open forming Replication Forks (Y-shaped area)
Parental DNA Molecule 3’ 5’

36. An enzyme (HELICASE) unzipsT A A T G C
A closer view of
DNA replication
looking at part
of a strand A T C G T A T A A T
An enzyme (HELICASE) unzips
the DNA molecule G C C G T A A T

37. T G C A T A
Single Strand binding proteins keep the two strands separated G
DNA
Strands
separate A C T T A G C T A

38. T A T A A T A T G C G C A T A T C G C G T A T A T A T A A T A T G C G
DNA POLYMERASE
ADDS NEW
NUCLEOTIDES
to form the new
side of the DNA
chain A T A T C G C G T A T A T A T A A T A T G C G C C G C G T A T A A T A T