Chapter 12 Genetic Engineering

12.1 Modifying 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 Strategies By selecting the most productive organism to produce the next generation people have found that the productivity of domesticated species can be increased

Selective Breeding Selecting a few individuals to serve as parents for the next generation The desired characteristic will become more common

Inbreeding Used once a “good” organism is produced Crossing of individuals with similar characteristics so that those characteristics will appear in the kids Organisms are usually closely related

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

Hybridization Cross between similar individuals Often involves crossing members of different but related species Hybrid vigor – hybrid individual are often hardier Example – corn – 10x more

Mutations – Producing new kinds of Organisms

Mutation – inheritable changes in the DNA Can produce organisms with new characteristics Breeders can wait for them to appear or cause them

Mutagen Substances that cause mutations Ex. Radiation, chemicals Works well with bacteria

Bacteria Very small Reproduce asexually Most abundant and diverse organisms in the world Some are helpful (bacteria in your intestines, bacteria that decompose dead organisms) Some are harmful (food poisoning, colds, infections)

Structure of Bacteria No membrane bound organelles Capsule – surround cell wall – bacteria with these are more likely to cause disease Cell wall – maintains the cell’s shape Pilli – help bacteria stick to surfaces Flagella – help bacteria move Chromosome – single DNA molecule – circular – contains most genes Plasmid – one molecule of circular DNA

Plasmid Small circular pieces of DNA found in bacteria in addition to their chromosomes Can be removed from bacteria and cut up using restriction enzymes A DNA sequence can be inserted into a plasmid Plasmids can be easily reinserted back into the bacteria

12-2 Genetic Engineering

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

Tools for Genetic Engineering 1. Way to cut a gene out of the DNA 2. Combine DNA with DNA of recipient organism 3. Insert combined DNA into new organisms 4. Way to read the sequences in order to analyze the genes you are manipulating

Restriction Enzymes (Endonucleases) Proteins that cut genes at specific DNA sequences each recognizes a specific spot EcoR1 – cuts at the AG site Bam1 – cuts at the GG site Hae111 – cuts between C and G

Action of a Restriction enzyme

DNA Recombination DNA 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

DNA Insertion Put recombinant DNA in a mix of bacterial cells Some 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 Organisms Transgenic – organisms that contain foreign genes

Transgenic Bacteria put genes in bacteria and they make things humans need Ex. Growth hormone

Transgenic Plants Produce natural insecticides Produce fertilizer

Transgenic Animals For farming, ranching Grow faster Disease resistant

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

12-3 The New Human Genetics

Curing genetic diseases – 5% of babies in USA born with one Decoding 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 2000 Personal Id Diagnosis of disease – 4,000 human genetic disorders

DNA Fingerprinting Takes 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 DNA The banding patterns of DNA fragments from two different individuals may be compared to establish whether they are related Can be used to match a criminal to a crime scene

Making a DNA Fingerprint RFLP analysis (Restriction Fragment Length Polymorphism) – method for preparing a DNA fingerprint RFLP analysis – involved extracting DNA from a specimen of blood or other tissue and cutting it into fragments using restriction enzymes The 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 requires Fragment of DNA Supply of the four nucleotides DNA 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 Cells Stem 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 Cells embryonic 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.