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