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I. Introduction
A. Evolution works through natural selection.
1. How does natural selection work?
a. Natural selection works through
genetics.
B. Genetics
1. How does genetics work? (How do you
get a phenotype from a genotype?)
a. Genetics works through gene
expression:
DNA --> RNA --> protein
C. Gene Expression
1. How does gene expression work?
a. DNA is used to make more DNA
and DNA is used to make RNA.
b. RNA is used to make proteins.
c. These processes depend on procedures
involving complementary base pairing.
II. RNA (Ribonucleic Acid)
A. Three Kinds of RNA
1. Messenger RNA [mRNA]
2. Transfer RNA [tRNA]
3. Ribosomal RNA [rRNA]
III. The Hereditary Code
A. The Code of Life
1. The sequence of bases on the DNA
molecule stores genetic information in a
coded form.
2. This information is transferred to a
mRNA molecule.
3. The coded information is then used to
make proteins.
a. Proteins are polymers (chains) of
amino acids (about 20 are used).
B. The process is similar to what happens in the
English language. (Letters make words
which make sentences that have some
meaning.)
1. The "Letters" (on DNA and RNA)
a. A, C, G, T and/or U
(signifying the nitrogen bases)
2. The "Words" making the "Sentence"
(on RNA)
a. Codons (Three-Letter "Words")
i. Triplet Code
a) Each codon consists of only 3
"letters" (bases).
ii. Each codon (base sequence "word")
on the mRNA molecule (the
"sentence") stores the information
for one of the 20 amino acids (the
"meaning of the word") making up
the amino acid sequence of a
protein (the "meaning of the
sentence").
iii. Degenerate Code
a) Since 4 letters (bases) taken
only 3 at a time can produce
64 different "words" (codons),
more than 1 codon can specify a
particular amino acid.
IV. Gene Expression
A. The "Central Dogma"
1. DNA is used to make RNA and RNA is
used to make proteins.
a. Transcription
i. DNA is used to make RNA.
b. Translation
i. RNA is used to make proteins.
B. Bad Dogma! Bad!
1. Reverse Transcription
a. RNA is used to make DNA and then
DNA is used to make RNA and
RNA is used to make proteins.
V. Transcription
A. Transcription of a Non-Segmented Gene
B. Transcription of a Segmented Gene
1. Exons
2. Introns ["Junk DNA"]
3. Primary Transcript
4. Editing and Splicing
VI. Translation
A. Each codon of the mRNA molecule is "read"
and the amino acid called for is put into place
in the forming polypeptide chain.
B. Process
1. Initiation
a. Ribosomes / Polyribosomes
b. tRNA
i. Anticodon
c. mRNA
i. Initiator Codon (AUG)
a) Methionine (met)
[in eukaryotes]
b) Formylated Methionine
(f-met) [in prokaryotes]
i) A formyl group is added to
methionine to produce
formylated methionine
(f-met)
2. Elongation
a. More amino acids of the chain are put
into place.
3. Termination
a. Termination Codon
(UAA, UAG, or UGA)
b. The last amino acid is put into place,
the protein chain is edited, and the
protein takes on its final shape.
VII. Regulation of Gene Expression
A. Structural Genes
B. Regulatory Genes
VIII. Summary
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