1. Chapter 12
DNA & Proteins

2. Components & Structure of DNA
DNA is a long molecule made up of nucleotides which contains:
Deoxyribose – 5 Carbon sugars
Phosphate
1 of four
Adenine – purine = double ring of C & N
Thymine – pyrimidine = single ring of C & N
Guanine – purine
Cytosine - pyrimidine

3. Chargraff – Amt. of A = Amt. of T
Important research that contributed to the discovery of the structure of DNA
Chargraff – Amt. of A = Amt. of T
Amt. of C = Amt. of G
Amt. of A, T, C, G varies between different organisms
Wilkins & Franklin- Studied X-ray diffraction
Studied the structure of DNA fibers
Revealed a tightly coiled helix w. 2 or 3 strands
(one of the first illustrations of DNA)

4. Watson & Crick Model was made of cardboard & wire
Used Chargraff’s & Franklin’s findings

5. Structure of DNA
Double helix – 2 strands twisted around a central axis
Each strand made of nucleotides
Held together by Hydrogen bases
Base pairing
A = T linked w/ 2 hydrogen bonds
G= C linked w/ 3 hydrogen bonds
This keeps the 2 strands together
Strands are complementary – sequence of bases on 1 strand determines the sequence of bases on the other

6. 12-2 Chromosomes & DNA Replication
Prokaryote DNA
single circular DNA = cell’s chromosome
Eukaryote DNA
1000x more than prokaryotes
Is in the form of chromosomes
Chromosome = chromatin=DNA +proteins
One DNA molecule = single chromosome

7. 12-3 RNA & Protein Synthesis
DNA carries the messages for protein synthesis
Genes – coded DNA instructions that control the production of proteins in all cells
Proteins carry out all the functions of the cell
To get this done:
DNA must be decoded → RNA

8. Ribonucleic acid Structure (RNA) (Compares/Contrast)
Single strand of nucleotides
Ribose is sugar that alternates w/ phosphate
Nitrogen bases – adenine, cytosine, guanine, uracil
No thymine
Can leave the nucleus
Has 3 Forms
mRNA – messenger RNA – carries instructions for making proteins
tRNA – transfer RNA – carries an amino acid to the ribosome
rRNA – ribosomal RNA – make up the ribosome

9. Protein synthesis – entire process by which proteins are made based on DNA info
Stage 1 – transcription
Stage 2 – translation
Transcription
Using DNA info to make mRNA
Occurs in nucleus
Translation
mRNA info is used to make a protein
Occurs in cytoplasm at the ribosome

10. 12-4 Mutations Mutation – any change in DNA Occurs in Gene mutations
Somatic cells – affect the individual
Gametes – affect the offspring
Gene mutations
Point mutation – changes 1 or more nucleotides in a gene
Substitution – one nucleotide is replaced by another
Can result in no protein or nonfunctioning protein
Some result in little or no effect
Frame shift mutation
Insertion – one or more nucleotides are added
Deletion – 1 or more are deleted
Results in message being read out of order

11. HECTHEERCATATERRAHCTHEACEACRARAT=gene
THE CAT ATE THE RAT normal sequence
THE CAT ATE THE HAT Substitution
THE CCA TAT ETH EHA Insertion
THC ATA THE HER AT Deletion

12. Chromosomal Mutation – change in the number or structure of chromosomes:
Deletion – loss of all or part of chromosome
Duplication – extra copies of parts of chromosomes
Inversion – reverse direction of parts of chromosomes
Translocation – one part breaks off & reattaches to a different chromosomes

13. Importance of Mutations
Most are neutral – have little or no effect
Some are harmful – make defective proteins that disrupt normal biological activity
Ex. Sickle cell anemia, cystic fibrosis, cancer
Some are beneficial – are the source of genetic variation
Ex. *resistance to HIV
*Polyploidy – an organism w/ an extra set of chromosomes
- often larger and stronger than diploid plants = bananas