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DNA: History, Structure, & Function
Nucleic Acids
I. DNA (Deoxyribonucleic Acid)
A. Overview of Griffith’s 1928 Experiment
Two types of Streptococcus pneumoniae
a. rough (non-virulent)
b. smooth (virulent)
B. First experiment
1. Rough serum
2. Smooth serum
C. 2nd experiment
1. Rough serum heated
2. Smooth serum heated
D. 3rd experiment
1. Live rough + heated smooth
2. Conjugation caused “transformation”
dead
smooth
live
rough
Transformed
from rough
a. DNA = “transforming principle,”
changes what cells look like and do
b. Mendel’s “partikles” = genes = nucleic acids
II. Structure of DNA
A. DNA – Deoxyribonucleic Acid
B. Composed of :
1. Phosphate, which is connected to a …
2. Sugar (Deoxyribose), which is connected to…
3. One of four nitrogenous bases
a.
b.
c.
d.
Adenine
Thymine
Guanine
Cytosine
Complementary Bases
Complementary Bases
II. Structure of DNA
C. Nucleotide
1. One unit of phosphate, sugar, and
base
2. One nucelotide base is connected
to another, complementary one,
by hydrogen bonds
3. This is called a “base pair”
D. Codon
1. Group of 3 nucleotides in a row
2. Each codon codes for placement
of one amino acid in a protein
II. Structure of DNA
E. Genes
1.
Group of codons on a chromosome that generally cod
for the production of a protein.
2.
There are different kinds of genes
a.
b.
c.
d.
Promoters – Help other genes work better
Structural – Contain coding of proteins used outside
Regulatory – Turn others off and on (how many?)
Operational – Used in the cell to make “local” products
F. Chromosomes
1.
Long strands of DNA, each with many genes
2.
One chromosome has +/- 20,000 genes on it.
3.
A typical human cell has 46 chromosomes in it
II. Structure of DNA
G. The Nucleus
1. Location in the cell in which most DNA is
contained.
2. Some DNA is
also found in the
mitochondria, or
energy making
structures of the
cell.
III. Function and Properties of DNA
A. DNA Replication
A. DNA can copy itself, using
free-floating pieces of
nucleic acid as building
blocks
B. Occurs in mitosis and
meiosis
III. Function and Properties of DNA
B. Protein Synthesis Overview
1. Structural proteins are the big structural components
of tissue (e.g. muscle, epithelial, etc.)
2. Enzymes are proteins that serve as catalysts, aiding
chemical reactions in the body.
3. Amino acids are the building blocks of protein.
1. There are 20 important amino acids.
2. Proteins differ according to number of amino
acids and the sequence in which they are
arranged.
III. Function and Properties of DNA
B. Protein Synthesis Overview, continued
4. Two basic steps to Protein Synthesis
a. Transcription (copying the message)
1. DNA partially unwinds
2. Free-floating RNAs “click in”, copying
3. Completed strand of mRNA breaks off
b. Translation (transporting and interpreting)
1. mRNA travels to ribosome
2. mRNA attracts tRNA with amino acids on them
3. amino acid chains form proteins
4. tRNA and mRNA return to their jobs
III. Function and Properties of DNA
C. Understanding Protein Synthesis
1. DNA and RNA as a language
Grammar
Letters
Words
Sentences
Paragraphs
Example:
THEFATCATATETHEREDRATENDTHEFATRATSATANDSATEND
III. Function and Properties of DNA
C. Understanding Protein Synthesis
2. Protein Synthesis: a manufacturing business
Crazy Industrialist in his “compound”
Trusted Relative/Messenger
The Factory
The Factory Workers
The Raw Materials
The Finished Product
III. Function and Properties of DNA
D. Mutation – a change in the genetic code
1. Point mutations – individual base changes
a. Substitution
b. Insertion or Deletion
Examples:
THEFATCATATETHEREDRATENDTHEFATRATSATANDSATEND
THEFATCATATETHEREDBATENDTHEFATRATSATANDSATEND
THEFATCATATETHEREDBRATENDTHEFATRATSATANDSATEND
THEFATCATATETHEREDATENDTHEFATRATSATANDSATEND
2. Chromosomal mutation – major change
a. Translocation
III. Function and Properties of DNA
3. Effects of mutation
a. Nothing
b. Slight change in gene product
c. Change for the better or worse
d. Lethal
4. Some causes of mutations:
Radiation, chemicals, UV light, random error