Chapter 10: DNA, RNA, and Protein Synthesis
Chapter 10: DNA, RNA, and Protein Synthesis
Objectives:
n Analyze and investigate emerging scientific issues (e.g., genetically modified food, stem cell research, genetic research and cloning).
n Describe advances in life sciences that have important long-lasting effects on science and society (e.g., biological evolution, germ theory, biotechnology and discovering germs).
I. DNA Structure
- Double helix
- Double twisted Ladder
- Watson and Crick
- Credited with discovering the structure of the DNA model
- 1953
II. DNA Nucleotides
A. Make up the long chains of the DNA Helix
a. Parts of the ladder
B. Consists of 3 parts:
a. Five carbon sugar (deoxyribose)
b. Phosphate group
c. Nitrogen base
III. Nitrogen bases
A. 4 Nitrogen bases make up DNA
a. T (thymine)
b. A (Adenine)
c. C (Cytosine)
d. G (Guanine)
B. Base pairing rules
a. Cytosine always pairs with Guanine
b. Guanine always pairs with Cytosine
c. Thymine always pairs with Adenine
d. Adenine always pairs with Thymine
IV. Example
n If you have the sequence
A
T
C
G
V. DNA Replication
A. Process by which DNA is copied before a cell divides
B. Steps:
C. Enzymes, called helicases, separate the DNA strand
D. Enzymes, called polymerase, add complimentary bases pairs (T’s to A’s etc.)
E. DNA polymerase fall off and there are 2 identical strands
A -
T -
C -
G -
A -
T -
C -
C -
VI. DNA errors in replication
A. Mutation
a. A change in the nucleotide sequence
b. Have serious effects on the function of cells
c. Mutations that are not repaired are called cancer
VII. Flow of Genetic Material
A. How does information from DNA get to cell?
a. DNA – RNA - protein
B. Transcription
a. DNA acts as a template for RNA synthesis
C. Translation
a. Directs assembly of proteins
D. Protein synthesis
a. Forming proteins bases on information
VIII. Protein Synthesis
- Steps:
- DNA double helix unwinds
- Messenger RNA comes and copies
- A (adenine) pairs with U (uracil)
- Other bases pairs combine with usual complimentary bases
- RNA codes for codons, (3 base pair) see chart
- Each codon is used to make an amino acids
- Each amino acid combination makes proteins
- Proteins control ALL functions of the cell!
n 10.4 Genetic Changes
n Mutation – any change in a gene or chromosome.
n *Leading cause of evolution.
n Mutations that occur in gametes can be inherited while mutations that occur in the body cells are not passed to offspring. You may have a genetic predisposition to the defect.
n Example Breast Cancer
n A. Types of mutations
n Point mutation – change in one base pair. AAT, AAC. ( the amino acids are leucine, still leucine) sometimes there is no effect on the protein
n Inversion – where two letters are switched. Instead of AAT you could get ATA. (leucine becomes tyrosine)
n Frameshift – when an entire sequence is altered.
u Deletion shifts the frame left – ATATTC, delete the A
You get TATTC
-Insertion shifts the frame to the right – ATATTC, add a T - you get TATATTC
n Insertion of a base or deletion of a base will cause frameshift mutations. Could affect the entire chromosome
n Translocation – piece of chromosome attaches to an entirely different chromosome.
n B. Causes of Mutations
n Spontaneous – just happen, no explanation
n Mutagens – things that can cause cancer. Such as: drugs, alcohol, smoke, pollution, radiation (sun & X-Ray, nuclear), chemicals (dioxins, asbestos, benzene, cyanide) and even high temperatures.
n Repairing DNA: Enzymes proof read and correct nucleotides, but the more mutations the more likely a mistake will be missed and not corrected. You need to limit your exposure to mutagens to reduce your risk of causing a mutation.