1. DNA: Structure and Function
Chapter 12
Section 1

2. The Molecule of Heredity The Blueprint of Life
DNA
Deoxyribose Nucleic Acid The Architect of Life
The First three-dimensional xerox machine
The Molecule of Heredity
The Blueprint of Life
Life Instruction Manual

3. DNA

4. Why Study DNA?
To truly understand genetics, biologists first had to discover the chemical structure of the gene
This would then help them understand how genes control the inherited characteristics of living things
Gene expression is what enables cells of the same organism to take on so many different sizes, shapes and functions
(even though just about every cell in an individual contains the same DNA)

5. Review What organelle is known as the control center of the cell?
What structures are found in the nucleus?
What are short segments of chromosomes?
4. What are genes/chromosomes composed of?
5. How do genes/chromosomes control the activity of the cell?
nucleus
chromosomes
genes
DNA
produce proteins that regulate cell functions and become cell structures

6. Review
Review

7. History 1869 - Friedrich Miescher – “discovered” DNA in nucleus
Frederick Griffith
History
Rosalind Franklin
X-ray of double helix
James Watson
Francis Crick
Martha Chase
Alfred Hershey
Friedrich Miescher – “discovered” DNA in nucleus
Frederick Griffith – Identified DNA as source of genetic material using bacteria
1930’s - Oswald Avery, Colin MacLeod and Maclyn McCarty - Confirmed that genes made of DNA
Alfred Hershey and Martha Chase confirmed DNA is the biochemical of heredity using radioactive markers bacteriophages
1952- Maurice Wilkins and Rosalind Franklin X-rayed DNA to show repeating nucleotide structure
1953- James Watson and Francis Crick combined data to create a 3-D model of structure called the double helix
Oswald Avery
Maclyn McCarty

8. Watson-Crick Model

9. DNA Structure Is a polymer of 1000’s of nucleotide monomers
Is a double strand of covalently bonded nucleotides in twisted ladder shape
twisted ladder shape = double helix

10. DNA Shape Double helix: 2 spirals wound around each other
But joined in the middle

11. DNA Structure Is a polymer of 1000’s of nucleotide monomers
Is a double strand of covalently bonded nucleotides in twisted ladder shape twisted ladder shape = double helix
‘Rungs’ of ladder = nitrogen bases
‘Sides’ of ladder = sugar & phosphate groups (also called the DNA backbone)
Sugar Phosphate Backbone

12. Nucleotide Nucleotide- Individual unit of DNA. Made of three parts:
Deoxyribose (5-carbon sugar)
Phosphate group
A nitrogen-containing base

13. Bases
Four nitrogen-containing bases
Adenine
Guanine
Cytosine
Thymine

14. Bases Adenine double ringed = Guanine purines Thymine single ringed =
Cytosine
purines
pyrimidines

15. Nucleotide
Deoxyribose (like ribose) is a sugar with 5 carbon  atoms in a ring
Oxygen is one of the ring members
In Deoxyribose, one of the OH groups is missing and replaced with hydrogen
Thus deoxy =
- 1 oxygen P
base
sugar H OH

16. Nucleotide P - the Phosphate group
Is important because it links the sugar on one nucleotide with the phosphate of the next nucleotide to make a polynucleotide
Nucleotides are connected to each other
via a covalent bond P
base
sugar

17. ‘Base Pairing Rule’ Bases are paired together in specific manner
Because of chemical structure and shape
Adenine only pairs with Thymine
Guanine only pairs with Cytosine
Exactly enough room for only one purine and one pyramide base between the two strands of DNA

18. ‘Base Pairing Rule’
Bases held together in ‘rungs’ by weak hydrogen bonds
2 hydrogen bonds between A & T
3 hydrogen bonds between C & G

19. DNA

20. DNA Function Scientists wondered how DNA worked.
They knew genes do these critical things:
Carry information from one generation to another
Put information to work to determine an organism’s characteristics
Can be easily copied
Store and transmit genetic information needed for all cell functions
In order to do these things it had to be a special molecule!

21. Understanding DNA Our knowledge of DNA put to use:
Inheritance/ Genetic Counseling
Cell function/protein synthesis
Embryonic development/gene regulation
Evolution/ phylogenetic relationships
Medicine/genetic diseases
Genetic engineering/ recombinant DNA

22. Structure of DNA Review
Nucleotide
Hydrogen bonds
Sugar-phosphate backbone
Key
Adenine (A)
Thymine (T)
Cytosine (C)
Guanine (G)

23. Structure of DNA Review
Pyrimidines
Purines
Adenine
Guanine
Cytosine
Thymine
Bases
Phosphate group
Deoxyribose

24. DNA’s Size
To get an idea of the size of the human genome present in each of our cells, consider the following analogy: If the DNA sequence of the human genome were compiled in books, the equivalent of 200 volumes the size of a Manhattan telephone book (at 1,000 pages each) would be needed to hold it all. It would take about 9.5 years to read out loud (without stopping) the 3 billion bases in one person's genome sequence, calculated on a reading rate of 10 bases per second, equaling 600 bases/minute, 36,000 bases/hour, 864,000 bases/day, 315,360,000 bases/year.
Human Genome Project

26. DNA How Am I Packaged? Nitrogen bases 1. Are like letters in the code
2. Put them in different order make a different gene

27. DNA Package Genes 1. Are like words made up of letters
HAT A
DNA
CAT
DOG
Package C A
Genes
1. Are like words made up of letters
2. A group of nitrogen bases that makes sense
3. Tells the cell to do something T

28. DNA The cat sat. One dog ate. The big hat. Package DNA strand
1. Are like sentences made up of words
2. A long line of genes on each DNA strand

29. DNA Package Chromosomes 1. Are like books full of sentences
2. DNA strand twists around and around itself

30. DNA Package Nucleus 1. Is like a bookcase
2. Inside the cell, where all the chromosomes are stored

31. DNA
Package
So what would a library full of rows and rows of bookcases represent?
many cells together
which is a tissue