1. History and Shape of DNA
Notes for in-class objectives & chapter 11

2. History
For hundreds of years scientists have searched for a molecule that transmits inherited traits from one generation to another
1944- Avery found that DNA stored information

3. History
1950s-Rosalind Franklin discovered the twisted shape of the molecule

4. History
1953- Watson and Crick find the molecule has a double helix shape

5. What is DNA? DNA stands for Deoxyribonucleic Acid
DNA is the genetic content of a living cell; the instruction manual for a living organism.
DNA contains directions for assembling amino acids into proteins
The molecule is subdivided into thousands of genes that each code for a trait

6. Important definitions
Proteins: carry out all structures and functions of a cell. Ex: gene for eye color, nose shape or cystic fibrosis
Heredity: The transmission of characteristics from parent to offspring.
Genes: A sequence of DNA that codes for a protein and determines a trait

7. Central Dogma of Molecular Biology
DNA RNA Protein

8. Forms of DNA:
Chromatin-the DNA is one long continuous strand of information
Chromosomes- the DNA is broken up into tightly wound X-shaped structures and moves around while the cell divides.

9. Each Chromosome can hold thousands of genes
Each person has 46 chromosomes and about 23,000 genes total

10. Structure of DNA
The molecule has a double twist- called a double helix

11. Subunits of DNA
A DNA molecule consists of billions of nucleotides bonded together

12. Nucleotide Made of 3 parts: Sugar Nitrogen Base Phosphate
DNA: Deoxyribose
RNA: Ribose
Nitrogen Base
Purines- Adenine and Guanine
Pyrimidines- Thymine and Cytosine
Phosphate

13. DNA is a twisted ladder Outside- a sugar-phosphate backbone
Inside- nitrogen containing bases
The N-bases are held together by hydrogen bonds (2 nucleotides = base pair)

14. Chargaff’s Rule
Adenine always bonds to Thymine, Cytosine always bonds to Guanine
Number of A = Number of T
Number of C = Number of G

15. Function of DNA
Control of cellular activities: DNA carries the code for assembling enzymes and the other proteins that function in the cell’s metabolism.
Replication: DNA replicates itself so that its genetic information is passed on. The genetic information lies in the sequence of the base pairs.

16. Steps of Replication
Unwind
Unzip
Insert
Proofread

17. DNA Replication
DNA replication: the DNA strand “unzips” the weak hydrogen bond comes undone and the base pairs separate.

18. Insert
After the DNA molecule opens up, new nucleotides are brought in and match up to their complimentary base. (A-T, C-G)

19. Proofreading
The nucleus has enzymes that “read” through the molecule looking for mistakes.
If one is found, the molecule cuts out the incorrect nucleotide and replaces it.
Even with this molecule, sometimes a mistake is made, causing a change.

20. Something old something new
The process is semi-conservative; each new molecule has one of the old strands and one of the new strands.

21. Modern DNA Research
Dolly the sheep and cloning.
britannica.com

22. Modern DNA Research Can we clone a T-rex?