1. DNA
The molecule of life

2. Look around the room….
List 5 differences between yourself and others in the room. 1. 2. 3. 4. 5.

3. What type of molecule is responsible for these differences?
PROTEIN
Skin and eye color pigment are due to the protein melanin.
Nose shape is due to the protein cartilage; strength due to protein of muscle
Lactase enzyme is a protein.
Growth hormone is a protein.
You are able to make 30,000 different proteins.

4. What are proteins made of?
Long chains of amino acids:

5. Where do these amino acids come from?
Your protein foods contain amino acids.
Cheese
Egg white
isoleucine
trypt
valine
alanine

6. There are 20 different amino acids found in your food.
Milk is a ‘complete protein’ - it has all the essential amino acids.
Rice and beans together make a ‘complete protein’.
The amino acids are absorbed from your gut into your bloodstream then enter your cells’ cytoplasm by diffusion. There they wait to be incorporated into a needed protein.
Without a complete set of amino acids in your cell at any given time, your cells can not make a required protein and you will suffer a deficiency = protein malnutrition.

7. WHERE are the recipes (genes) that tell a cell how to put together the amino acids that are waiting in the cytoplasm of each cell, into the correct order to make a specific protein?
Options:
Cytoplasm?
Nucleus?

8. How do your cells know how to build each specific kind of protein?
Insulin amino acid sequence:
meth
Asp.
acid
valine

9. Griffith Experiment conducted in 1928
Virulent (infectious) and avirulent (non-infectious) strains of bacteria
What can we conclude from his results?

10. Avery, MacLeod and McCarty
Continued Griffith’s experiment in 1944
Isolated components of S (virulent) strain
What conclusions can be made from their results?

11. Hershey and Chase Alfred Hershey and Martha Chase - 1952
Studied bacteriophage; a virus that invades bacteria
Labeled protein with radioactive sulfur
Labeled DNA with radioactive phosphorus
What can we conclude from their results?

12. Watson, Crick and Franklin
Rosalind Franklin worked on x-ray crystallography pictures of DNA to determine its structure
James Watson and Francis Crick took these photographs and used them to determine the structure of the DNA molecule

13. Questions?

14. DNA = Deoxyribnucleic Acid
So the molecule that holds the ‘recipes’ on how to build proteins is the double helix
DNA = Deoxyribnucleic Acid
DNA is a nucleic acid

15. DNA is made of subunits called nucleotides
Each nucleotide is made up of:
1.) a nitrogenous base (single or double ringed)
2.) a 5 carbon sugar (deoxyribose)
3.) a phosphate group

16. There are 4 different types of nucleotides in DNA
The 4 types of nucleotides are the same except each has a different nitrogenous base
Pyrimidine = 1 carbon ring
Purine = 2 carbon rings
The 4 nitrogenous bases in DNA are:
Adenine
Thymine
Guanine
Cytosine P
Base S

17. Nucleotides bond together to form a chain
Nucleotides bond together between their sugar and phosphate groups to form a polynucleotide chain

18. 2 chains of nucleotides bind to form a DNA molecule
Hydrogen bonds form between the nitrogenous bases to join the 2 chains together
The sugar and phosphate group together is known as the sugar-phosphate backbone

19. Chargaff’s Discovery
He found that the amount of adenine always equaled thymine and that the amount of guanine always equaled cytosine
However the amount of A+T often did not equal the amount of C+G
What do you think that he was able to conclude from this?

20. Complimentary base pairing
Adenine always pairs with Thymine
Cytosine always pairs with Guanine
The 2 strands are joined by weak hydrogen bonds.

21. Interesting facts….
There are 46 pieces of DNA in each nucleus (23 from mom, 23 from dad).
One cell contains enough DNA to wrap around the circumference of the earth.
One cell’s DNA contains 3 billion base pairs.

22. What is the complementary base sequence on the other strand of the DNA?
A T T G C C C T A A

23. Test questions:
So, If a section of DNA consisted of 30 nucleotides, and 10 of them were adenine nucleotides, how many thymine, guanine, and cytosine nucleotides are there?
If the insulin gene consists of 40 base pairs, and 32 adenine nucleotides were present, how many guanine, cytosine, and thymine nucleotides are present.
Answer: 10 thymine, 5 guanine and 5 cytosine
Answer: 32 thymine, 8 cytosine, and 8 guanine

24. The classic picture of a DNA strand
The classic picture of a DNA strand. You should now be able to recognize:
Sugar-phosphate backbone
Nitrogenous bases
the 4 types
Purines and Pyrimidines
2 chains of nucleotides
Base-pairing rules