Chapter 12

Genetic Engineering

12.1Modifying the Living World

Humans are always trying to improve their world

What are some desired traits that breeders might want to select for in these food sources?What would breeders need to know about each trait to produce the desired trait in the offspring?

Breeding StrategiesBy selecting the most productive organism to produce the next generation people have found that the productivity of domesticated species can be increased

Selective BreedingSelecting a few individuals to serve as parents for the next generationThe desired characteristic will become more common

InbreedingUsed once a “good” organism is producedCrossing of individuals with similar characteristics so that those characteristics will appear in the kidsOrganisms are usually closely related

Risks of InbreedingBecause organisms are genetically similar, the chances of recessive defects showing up are higher

HybridizationCross between similar individualsOften involves crossing members of different but related speciesHybrid vigor – hybrid individual are often hardierExample – corn – 10x more

Mutations – Producing new kinds of Organisms

Mutation – inheritable changes in the DNACan produce organisms with new characteristicsBreeders can wait for them to appear or cause them

MutagenSubstances that cause mutationsEx. Radiation, chemicalsWorks well with bacteria

BacteriaVery smallReproduce asexuallyMost abundant and diverse organisms in the worldSome are helpful (bacteria in your intestines, bacteria that decompose dead organisms)Some are harmful (food poisoning, colds, infections)

Structure of BacteriaNo membrane bound organellesCapsule – surround cell wall – bacteria with these are more likely to cause disease

Cell wall – maintains the cell’s shapePilli – help bacteria stick to surfacesFlagella – help bacteria moveChromosome – single DNA molecule – circular – contains most genes

Plasmid – one molecule of circular DNA

PlasmidSmall circular pieces of DNA found in bacteria in addition to their chromosomesCan be removed from bacteria and cut up using restriction enzymesA DNA sequence can be inserted into a plasmidPlasmids can be easily reinserted back into the bacteria

12-2 Genetic Engineering

Last three decadesPowerful new set of techniques that affect DNA directlyBiologists can engineer a set of genetic changes directly into an organisms DNA – Genetic Engineering

Tools for Genetic Engineering1.Way to cut a gene out of the DNA2.Combine DNA with DNA of recipient

organism3.Insert combined DNA into new

organisms4.Way to read the sequences in order

to analyze the genes you are manipulating

Restriction Enzymes (Endonucleases)Proteins that cut genes at specific DNA sequences75+ - each recognizes a specific spotEcoR1 – cuts at the AG siteBam1 – cuts at the GG siteHae111 – cuts between C and G

Action of a Restriction enzyme

DNA RecombinationDNA fragments are incorporated into part of the recipient cell’s genetic material

Plasmid – small circular DNA molecule in bacteria

Sticky Ends – single strands of DNA that allow a gene to be inserted into a plasmid

G G T T A T C G C T T A G C G A T C G A GENE

Recombinant DNA – combined DNA of two organisms

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DNA InsertionPut recombinant DNA in a mix of bacterial cellsSome bacteria will pick up the DNA

Clone – large numbers of cells grown from a single cell

Other ways – injection with a needle - shot into cells

Foreign DNA into Plasmid

Engineering New OrganismsTransgenic – organisms that contain foreign genes

Transgenic Bacteriaput genes in bacteria and they make things humans needEx. Growth hormone

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Transgenic PlantsProduce natural insecticidesProduce fertilizer

Transgenic AnimalsFor farming, ranchingGrow fasterDisease resistant

Cloned Animals“Dolly”Nucleus of an egg is removed and replaced with an adult nucleusEgg is then placed into a foster momThe newborn is a clone – a genetic copy

12-3 The New Human Genetics

Curing genetic diseases – 5% of babies in USA born with oneDecoding the human genome (determine the nucleotide sequence of about 3 billion nucleotides or about100,000 genes and to map their location on every chromosome)Completed in June 2000Personal IdDiagnosis of disease – 4,000 human genetic disorders

DNA FingerprintingTakes advantage of the fact that large portions of the human genome are made of repeat sequences Repeat sequences have varying lengths do not code for a protein

A DNA fingerprint – a pattern of bands made up of specific fragments from an individual’s DNAThe banding patterns of DNA fragments from two different individuals may be compared to establish whether they are relatedCan be used to match a criminal to a crime scene

Making a DNA FingerprintRFLP analysis (Restriction Fragment Length Polymorphism) – method for preparing a DNA fingerprintRFLP analysis – involved extracting DNA from a specimen of blood or other tissue and cutting it into fragments using restriction enzymesThe number of fragments and the length of the fragments varies from person to person

Gel Electrophoresis – used to separate the fragments of DNA An electric current is passed through a gel and the fragments sort out by size

The Electric Field

The Fragments Move

Who are the Soldier’s parents?

Polymerase Chain Reaction (PCR)

Can be used to quickly make many copies of selected segments of the available DNA

PCR requiresFragment of DNASupply of the four nucleotidesDNA polymerase (enzyme involved in DNA replication)Primers

Primer – an artificially made single-stranded sequence of DNA required for the initiation of replication

When all the ingredients are added together the fragment of DNA is quickly multiplied

Stem CellsStem cells can develop into many different cell types in the body during early life and growth.Serve as an internal repair system, dividing essentially without limit to replenish other cells When a stem cell divides, each new cell has the potential either to remain a stem cell or become another type of cell with a more specialized function, such as a muscle cell, a red blood cell, or a brain cell

Two important characteristics of stem Cells

Unspecialized cells capable of renewing themselves through cell division, sometimes after long periods of inactivity. Under certain physiologic or experimental conditions, they can be induced to become tissue- or organ-specific cells with special functions

Two Types of Stem Cellsembryonic stem cells non-embryonic "somatic" or "adult" stem cells.

In the 3- to 5-day-old embryo, called a blastocyst, the inner cells give rise to the entire body of the organism, including all of the many specialized cell types and organs such as the heart, lung, skin, sperm, eggs and other tissues.In some adult tissues, such as bone marrow, muscle, and brain, populations of adult stem cells generate replacements for cells that are lost through normal wear and tear, injury, or disease.

Given their unique regenerative abilities, stem cells offer new potentials for treating diseases such as diabetes, and heart disease. Much work remains to be done in the laboratory and the clinic to understand how to use these cells for cell-based therapies to treat disease, which is also referred to as regenerative or reparative medicine.