CHAPTERS 15 & 16
Control & Manipulation of Genes
GENE CONTROLS Before Transcription
Access Acetylation loosens grip of histone, allowing
access of polymerase to DNA Methylation of an allele blocks that gene’s affect
How transcribed Gene sequences rearranged or multiplied,
generate large amounts of gene product
GENE CONTROLS Transcription Processing
mRNA cannot pass out of nucleus without transport protein
Some proteins can block translation from starting
Translation ControlAffect ribosome components (no rRNA, no
translation)Control speed of breaking down mRNA (how
many times it can be reused)
GENE CONTROLS X Chromosome
InactivationFemales XXOne X chromosome
is 75% “shut down”Barr body—
condensed X chromosome
Random
GENE CONTROLS—PROKARYOTES Operon—arrangement of promoter and
operators that control access to a gene Lac operon in E. coli cells
E. coli normally doesn’t use lactose (milk sugar)
Lac operon binds to gene that would allow use of lactose, prevents it’s transcription
When glucose is scarce but lactose present, activator is synthesized
Activator then prevents lac operon from functioning, allowing lactose to be used
Inhibition can be reversed
MANIPULATING DNA Recombinant DNA—any DNA molecule
consisting of base sequences from two or more organisms of the same or different species.
Able to combine genetic sequence of different species
Restriction enzymes Plasmids & cloning vectors
RESTRICTION ENZYMES A restriction enzyme is added to a
solution with DNA Enzyme “cuts” DNA at a specific place Can fuse with DNA molecule “cut” with
same enzyme
RESTRICTION ENZYMES
PLASMIDS Bacteria have two forms of DNA
One chromosome, a single circular DNA strand
Plasmids—small circles of “extra” DNA with only a few genes
Bacteria divide rapidly, providing many new organisms in a short period of time.
PLASMIDS In nature, bacteria can share
characteristics through plasmidsAntibiotic resistance
PLASMIDS With restriction
enzymes, can splice DNA into plasmid
Plasmid taken into bacteria cells
PLASMIDS “Donor” gene is
used by bacteria, produces product of gene
Is now part of bacteria’s genetic code, is passed on during division
PLASMIDS Uses
Laboratory studies of specific genesProduce products quickly & cheaply
Insluin Antibiotics
Vaccines Animal diseases HIV Ebola
PCR Polymerase Chain Reaction (PCR)—
method to reproduce fragments of DNA millions or billions of time
Primer—short stretch of synthetic, single-stranded DNA
PCR Primers are added to solution with DNA
fragments and polymerase Solution is heated, denaturing and
“opening” DNA Solution is cooled Primers attach to matching base pairs
during cooling Polymerase starts at primer, synthesizes
DNA chain Process is repeated
PCR Each “cycle” results in exponential
growth Quickly grow a segment of DNA
PCR Uses
ForensicsDiagnostics (viral & bacterial diseases)Paternity or relationship testingHistorical analysis
Mummies, mammoths, etc.
GEL ELECTROPHORESIS DNA is mixed with
certain compounds in a solution
The solution is placed into a gelatinous substance
Electrical charge is carried along the gel
The DNA separates along the gel in a pattern based on the structure and weight of the individual genes
DNA FINGERPRINTING Everyone’s DNA is
unique to them Base-pair patterns
different between people
PCR & electrophoresis to find & analyze DNA
1 in 3,000,000,000,000 chance of unrelated people having identical DNA
HUMAN GENOME PROJECT 1988—National Institutes of Health
combined previously begun research into one project
2003—Human genome officially completed
Almost 20,000 confirmed genes Over 2,000 possible genes Don’t know what all of these genes
do! Much of human genome DOESN’T
code for proteins Many might regulate expression of
other genes…. “Master Control” genes
HUMAN GENOME PROJECT Study diseases & disorders Be able to predict and detect disease Gene therapy—transfer one or more
normal or modified genes into a person’s body cellsCorrect genetic defectBoost resistance to disease Imperfect at this time
GENETIC ENGINEERING Bacteria
InsulinBlood-clotting factorsHemoglobinVaccinesEnvironmental clean-up
Oil spills Pollutants Radioactive waste
GENETIC ENGINEERING Plants
Drought resistanceDisease resistanceHerbicide resistanceSoil toleranceGreater yieldBetter nutrition
GENETIC ENGINEERING Animals
Medical research Mice susceptible to
human diseasesDisease resistanceEnvironmental
resistance Featherless chickens
Medical proteins Cattle—human collagen
(cartilage, bone, skin repair)
Better nutrition Low-fat pigs