2. T--A--C--A--A--G--T--A--C-- T--T--G--T--T--T--C--T--T--A--A—A
A- U –G U U C A –U – G A –A –C A A A – G U U U U U
Amino:
MET - ALA MET TYR LYS VAL PHE

3. G instead of C Missense AND NONSENSE
T--A--C--A--A--C--T--A--C-- T--T--C--T--T--T--C--T--T--A--A—A
A- U –G U U G A –U – G A –A –G A A A – G U U U U U
Amino:
MET - LEU MET STOP LYS VAL PHE

4. Deletion: FRAMSHIFT
T--A--C--A--A--G--T--A--C-- T--T--G--T--T--T--C--T--T--A--A—A
A- U –G U U C A –U – G A –A –C A A A – G U U U U U
Amino:
MET - ALA MET TYR LYS VAL PHE
MUTANT DNA:
T--A--C--A—A---T--A--C-- T—T---T--T--T--C--T—TAA – A
A U G U U A U C G AAA AGA AUU 
MET TYR SER LYS ARG PHE

5. Genetic Code

6. Gene Expression: Prokaryotes and Eukaryotes
AP Biology
Ch 18

7. s

8. x

9. c

10. Gene  Protein Control
Feedback inhibition – enough product is made the system shuts down
More product is made when needed
The product shuts down the process
Gene Expression – genes are only expressed when needed. Often regulated at transcription.
Figure 18.20a, b
(a) Regulation of enzyme activity
Enzyme 1
Enzyme 2
Enzyme 3
Enzyme 4
Enzyme 5
Regulation
of gene
expression
Feedback
inhibition
Tryptophan
Precursor
(b) Regulation of enzyme production
Gene 2
Gene 1
Gene 3
Gene 4
Gene 5 –

11. Gene Expression: Prokaryotes
Operon – grouped genes that are transcribed together – code for functionally similar proteins
Key Players
Promoter – section of DNA where RNA polymerase binds
Operator – Controls activation of transcription
on off switch
between promoter and genes for proteins – structural genes
Repressor protein – binds to operator to block RNA polymerase and shut down transcription
Turns off the operon
Corepressor – keeps the repressor protein on the operator
Trp operon
Inducer – pulls repressor off the operator
Turns on the operon – lactose on the lac operon
Regulatory gene – produces the repressor protein
Structural genes – code for proteins

12. Positive and Negative Gene Regulation
E. coli prefer to use glucose for energy, they will only use lactose when glucose is in short supply
glucose cAMP binds to regulatory protein “CAP” & stimulates gene transcription
Positive gene regulation!
The cAMP & CAP combination allow RNA polymerase to bind to the promoter sequence more efficiently.]
Remember cAMP is regulating the gene expression in the bacteria
Negative
Repressible: usually on but can be inhibited trp operon, allosteric inhibition, tryptophan present prevents its own production. (anabolic)
Inducible: usually off, but can be turned on, an inducer (a specific small molecule, allolactose in the lac operon) inactivates the repressor and allows transcription (catabolic)

14. Eukaryotic Chromosome

15. Eukaryotic Chromosome
Chromosomes – tightly coiled DNA around proteins during cell division
Chromatin – loosely packed DNA around proteins
Histones – protein which the DNA wraps around
Nucleosomes – grouped histones together
Heterochromatin – tighter packed chromatin
Not transcribing
Euchromatin – looser packed chromatin
Transcription occurring

16. Gene Expression: Eukaryotes
Cell Differentiation – cell specialization
All cells contain the same genes
The genes that are expressed determines the type of cell
Ex: Skin cell vs. a nerve cell

17. Chromatin Regulation
Histone acetylation – allows transcription factors to bind to DNA allowing transcription to occur
Creates loosely packed DNA - euchromatin
DNA Methylation – occurs after DNA synthesis has occurred
Lower transcription rates
One X in females is highly methylated (XX vs XY)

18. Epigenetic inheritance
Not controlled by base sequences.
DNA methylation (deactivates one homologous chromosome) may explain abnormal or unexpected DNA expression as is often seen in identical twins.

19. Regulation of Transcription
Transcription involves RNA Polymerase and transcription factors
RNA polymerase attaches to the promoter (TATA box) sequence to begin transcription
Control elements – non coding sequences of DNA where the transcription factors attach

20. Regulation of Transcription 18_Animations\18_09TranscripInitiation_A
Regulation of Transcription 18_Animations\18_09TranscripInitiation_A.swf
Enhancer – control element far from a gene or intron
Activator – bind to enhancers to turn on transcription of a gene
Transcription factors + enhancer + activator + RNA Polymerase = transcription initiation complex
Needed for transcription to begin
Repressors – inhibit gene expression
Turn off transcription
Block activators from binding to enhancers

21. brings the bound activators closer to the promoter.
Distal control
element
Activators
Enhancer
Promoter
Gene
TATA
box
General
transcription
factors
DNA-bending
protein
Group of
Mediator proteins
RNA
Polymerase II
RNA synthesis
Transcription
Initiation complex
Chromatin changes
RNA processing
degradation
mRNA
Translation
Protein processing
and degradation
A DNA-bending protein
brings the bound activators
closer to the promoter.
Other transcription factors,
mediator proteins, and RNA
polymerase are nearby. 2
Activator proteins bind
to distal control elements
grouped as an enhancer in
the DNA. This enhancer has
three binding sites. 1
The activators bind to
certain general transcription
factors and mediator
proteins, helping them form
an active transcription
initiation complex on the promoter. 3

22. RNA Processing Regulation 18_Animations\18_11RNAProcessing_A.swf
Alternative RNA Splicing – different regions of the pre-mRNA serve as introns or exons creating different mRNA strands depending on what is spliced out.

23. Protein Degradation 18_Animations\18_12ProteinDegradation_A.swf
Proteosomes – break apart proteins in to smaller peptide units
Chromatin changes
Transcription
RNA processing
mRNA
degradation
Translation
Protein processing
and degradation
Ubiquitin
Protein to
be degraded
Ubiquinated
protein
Proteasome
and ubiquitin
to be recycled
Protein
fragments
(peptides)
Protein entering a
proteasome

24. Constantly Active Genes
Oncogene – cancer causing gene
Proto-oncogene - normal gene that regulates cell division and growth
Proto-oncogene  oncogene = cancer
Certain viruses can be incorporated into DNA and increase cancer

25. G Protein & ras gene 18_Animations\18_15bbCellSignaling_A.swf
G protein: A protein that binds GTP ( a cellular energy source).
GTP transfers its phosphate groups to other molecules and releases energy in the process
Crucial in cell signaling a ras gene mutation triggers protein production of a protein that stimulates the cell cycle = cancer

26. Human Genome Exons (regions of genes coding
for protein, rRNA, tRNA) (1.5%)
Repetitive
DNA that
includes
transposable
elements
and related
sequences
(44%)
Introns and
regulatory
(24%)
Unique
noncoding
DNA (15%)
DNA
unrelated to
(about 15%)
Alu elements
(10%)
Simple sequence
DNA (3%)
Large-segment
duplications (5-6%)

27. Compare and Contrast Gene Regulation in Prokaryotes and Eukaryotes