1. Genetic Material: DNA and RNA DNA and RNA = hereditary
material first discovered in the nuclei of cells nucleotide
building blocks
2. Nucleotides : building blocks of DNA and RNA 1) Phosphate
group 2) Sugar (deoxyribose or ribose) 3) Base Purines (A,G) two
rings Pyrimidines (T,C,U) one ring 3. DNA structure: the double
helix Watson & Crick: DNA structure Double stranded double
helix Backbone = alternating sugar and phosphate Bases form the
rungs of ladder Complementary base pairing 4. DNA structure: the
double helix Antiparallel strands (opposite orientation) 3 end =
end with the OH attached to the 3 carbon 5 end = end with the
phosphate attached to the 5 carbon Strands run 5---------3
3---------5 5. DNA replication DNA is replicated 5 3 DNA polymerase
6. RNA Structure Different from DNA in that it: Is usually
single-stranded Only double-stranded in some viruses A rio virus?
DNA is single stranded in some viruses Contains ribose instead of
deoxyribose Contains uracil instead of thymine Three types found in
cells: mRNA rRNA (ribosyl) 50S and 30S tRNA Bottom is H a 7.
Protein Synthesis Question: How is info from DNA used to dictate
the activities of the cell? Answer: expression of proteins through
transcription and translation Transcription = synthesis of
complementary RNA from DNA Translation = synthesis of proteins
through decoding of mRNA 8. Transcription: DNA to mRNA Single
stranded mRNA synthesized from DNA template Synthesized 5 to 3
Complementary to template DNA Remember, uracil instead of thymine
in RNA Steps: 1. RNA polymerase binds the promoter 2. Synthesis
continues until the terminator is reached 3. mRNA can now be used
in the translation process 4. Operator: 9. Helicase pulls strands
apart 10. Translation: mRNA to protein Translates the nucleic acid
sequence into an amino acid chain Codons = groups of 3 nucleotides
that code for a particular amino acid - Start codon = initiates
protein sythesis - Stop codons = terminate protein synthesis
Genetic code is degenerate because there are more codons than amino
acids, they are not unique Last letter is called a wobble because
it can change, but the chances the amino acid will change is low
AUG codes for 11. Translation: mRNA to protein The process of
reading mRNA codons and generating the amino acid chain takes place
in the ribosome tRNA molecules transport amino acids to the
ribosome Anticodon = 3 base sequence complementary to a codon -
pairs to the complementary codon on mRNA - carries the amino acid
of the codon it recognizes anticodon Bound amino acid 12.
Translation: mRNA to protein 1. Ribosomal subunits assemble on mRNA
strand 1. Starts at P (pairing) site 2. AUG of mRNA is matched to
tRNA with proper anticodon 3. Another tRNA carrying the 2nd amino
acid arrives 13. Translation: mRNA to protein 4. The second codon
pairs with the anticodon of 2nd tRNA 5. A peptide bond forms
between the amino acids 6. Ribosome moves, opening up space for
another tRNA 14. Translation: mRNA to protein 7. The ribosome
reaches a stop codon, releases polypeptide 9. Last tRNA is
released; ribosome subunits dissociate; new protein! Stop codons do
not have tRNA 15. Regulating Gene Expression Transcription and
translation are steps in gene expression (DNA functional protein)
Are all genes expressed all the time? No How does the cell decide
when to express proteins? Constitutive genes = not regulated so
have constantly expressed protein products (~60-80% of genes) Other
genes are regulated by control mechanisms Things like the
cytoskeleton are needed all the time, so the genes are always
turned on and expressed 16. Inducible genes Genes that are turned
on because it has been triggered to turn on 17. Repression inhibits
gene expression by action of a repressor - Blocks RNA polymerase
from initiating transcription Usually a response to buildup of a
product of a metabolic pathway decreases synthesis of the enzyme
producing the product Example: E. coli trp operon Requires a
corepressor (Tryptophan) 18. When tryptophan is NOT abundant
Operon: group of genes that are under control by a single promoter
19. When tryptophan is abundant RNA polymerase Corepressor has to
bind to repressor to change its shape to make it functional
Repressors are always there (constituent), but are not turned
on/off until something acts on it 20. Induction turns on
transcription of a gene by an inducer - Binds the repressor and
keeps it from blocking transcription ends repression on synthesis
of the enzyme needed for metabolism of a particular substrate Ex)
E. coli beta-galactosidase (Lac operon) Inducer = lactose or
allolactose (analog) 21. When lactose inducer is NOT present LAC
operon 22. When lactose (or analog) inducer is present 23. Mutation
Mutation = A change in the base sequence of DNA may be neutral,
beneficial, or harmful Provides genetic variation for natural
selection Mutagen = Agent that causes mutations Spontaneous
mutations: Occur in the absence of a mutagen 24. Types of Mutations
in DNA Base substitution (point mutation) - Change in one base,
replaced with a different base Missense - Result in change in amino
acid Nonsense A base substitution, which results in a stop codon
Frameshift - Insertion or deletion of one or more nucleotide pairs
25. Figure 8.30a, b Transposons Transposons = jumping jeans
segments of DNA that can move from one region of DNA to another -
Contain insertion sequences for cutting and resealing DNA - Complex
transposons carry other genes - Stuck between inverted repeats 26.
Bacterial Gene Transfer: Conjugation Conjugation = transfer of
genetic material from one bacterial cell to another in the form of
a plasmid Plasmid = circular piece of DNA that replicates
independently from the chromosomes Requires direct cell-to-cell
contact: Sex pilus = projection from surface of donor cell that
contacts surface of recipient cell to bring them into contact F for
fertility 27. Example: E. coli fertility (F) factor plasmid Donor
(F+) cell carrying the plasmid transfers the plasmid to a recipient
(F-), which becomes F+ Importance: acquired DNA by recipient adds a
new function, like antibiotic resistance, etc. Plasmid is
replicated through rolling circle replication 28. Antibiotic
Resistance Misuse of antibiotics selects for resistance mutants -
This can happen from: Using outdated or weakened antibiotics Using
antibiotics for the common cold and other inappropriate conditions
Using antibiotics in animal feed Failing to complete the prescribed
regimen Using someone else's leftover prescription
