2. Pages:
Evolution: The Role of DNA

3. Deoxyribonucleic Acid
DNA
Deoxyribonucleic Acid

4. Vocabulary DNA Nucleotide DNA strand Double helix
Sugar – phosphate backbone
Nitrogenous base
Complementary Base Pairing
A gene
A protein

5. The Structure of DNA

6. DNA – The Molecule of Life
DNA is the genetic blueprint of life

7. DNA – The Molecule of Life
DNA is the genetic blueprint of life.
In every living cell, chromosomes can be found that contain the DNA and genes that govern the cell.

8. Several people were important in discovering DNA and its structure

9. Martha Chase and Alfred Hershey

10. Demonstrated that DNA and not PROTEINS is the genetic material

11. Hershey-Chase Experiments

12. Erwin Chargaff Watson and Crick knew:
3. A chemist, Erwin Chargaff, had determined in the late 1940s that the number of purines (ADENINE + GUANINE) in DNA always equals the number of pyrimidines (TYROSINE + CYTOSINE).
Further, the amount of ADENINE equals the amount of THYMINE (A = T), and the amount of GUANINE equals the amount of CYTOSINE (G = C)

13. Erwin Chargaff 1. ADENINE + GUANINE = THYMINE + CYTOSINE
2. ADENINE = THYMINE
GUANINE = CYTOSINE

14. It showed that DNA is a double helix.
Rosalind Franklin
prepared an X-ray diffraction photograph of DNA
It showed that DNA is a double helix.

15. James Watson and Francis Crick
DNA Structure and Replication
James Watson and Francis Crick

16. DNA Structure and Replication
- Watson and Crick built an actual model of DNA out of wire
and tin.
- This model does indeed allow for differences in DNA structure between species because the base pairs
can be in any order.
Also, the model suggests that complementary base pairing plays a role in the replication of DNA.
“It has not escaped our notice that the specific pairing we have postulated immediately suggests a possible copying mechanism for the genetic material.”

18. Overview of DNA
James Watson and Francis Crick determined the structure of DNA in 1953
DNA is a long chain of nucleotides
The chain is called a DNA strand (How many strands are there?)
The two strands form a spiraling ladder, also known as a double helix.
Nucleotides bond to each other to hold the strands together

19. Long Chain of Nucleotides

20. Nucleotide Each nucleotide is a complex of three subunits
Phosphoric acid (phosphate group)
A pentose (5 carbon) sugar (deoxyribose)
A nitrogen-containing base (nitrogenous base)

21. DNA Structure and Replication
Nucleotide
DNA Structure and Replication
Phosphate
group
Nitrogenous
base
Sugar

22. 2 DNA strands form Double Helix
Phosphate + Sugar = the sides of the ladder = Sugar – Phosphate Backbone
Nitrogenous Base = the steps of the ladder

23. Nitrogenous Bases Adenine will only pair up with Thymine
There are four types of nitrogenous bases
which make up the center rungs of the DNA
double helix;
Adenine (A)
Guanine (G)
Cytosine (C)
Thymine (T)
Adenine will only pair up with Thymine
Guanine will only pair up with Cytosine

24. COMPLEMENTARY BASE PAIRING
There are four types of nitrogenous bases
which make up the center rungs of the DNA
double helix;
Adenine (A)
Guanine (G)
Cytosine (C)
Thymine (T)
Adenine will only pair up with Thymine
Guanine will only pair up with Cytosine

25. What is a gene and protein?
It is a section or a part of DNA which codes for a particular protein
Proteins are chains of amino acids and they perform most of the functions in your body!

26. What is a gene and protein?
GENE is a section or a part of DNA which codes for a particular protein
Proteins are chains of amino acids and they perform most of the functions in your body!

27. What is a gene and protein?
For example:
A gene can code (has
information) for a protein
which gives you different
traits (characteristics): an
eye color, short fingers, long
neck, blond hair…etc

28. Genes – DNA - Traits
Genes are determined by the DNA molecule, and traits (characteristics) are determined by genes. This means that DNA determines your traits

29. Examples of Traits
Long Neck

30. Examples of Traits
Long Neck
Blue Eyes

31. Examples of Traits
Long Neck
Blue Eyes
Dark Skin

32. Examples of Traits
Long Neck
Blue Eyes
Dark Skin
Short Tail

33. Examples of Traits Long Neck Blue Eyes Dark Skin Short Tail
5 fingers on a hand

34. HOMEWORK
Molecular Genetics (Section 1) – reading notes
Take Home Quiz