PreAP Application of Genetics 2015

Gene Therapyhttp://news.discovery.com/human/videos/how-does-gene-therapy-work-video.htm

Testing for Alleles

Genetic disorders have slightly different DNA sequences from their normal counterparts. A variety of genetic tests have been developed

that can spot those differences. Enables prospective parents to see if they are

carriers of a genetic disorder such as Tay-Sachs or cystic fibrosis.

Genetic Tests

Genetic tests are now available for hundreds of disorders.Makes it possible to determine

whether prospective parents risk passing such alleles to their children.

Can pinpoint the exact genetic basis of a disorder, and therefore make it possible to develop more effective treatment.

Gene TherapyGene Therapy - Process of

changing the gene that causes a genetic disorder in order to eliminate the cause of the disorderAn absent or faulty gene is

replaced by a normal, working gene.

Replacing a mutated gene: A gene called p53 normally prevents tumor growth in your body. If

doctors could replace the defective p53 gene, that might trigger the cancer cells to die.

Fixing a mutated gene: Mutated genes that cause disease could be turned off so that

they no longer promote disease, or healthy genes that help prevent disease could be turned on so that they can inhibit the disease.

Making diseased cells more evident to the immune system.  In some cases, your immune system doesn't attack diseased cells

because it doesn't recognize them as intruders. Doctors could use gene therapy to train your immune system to recognize the cells that are a threat.

History of Gene Therapy

1990 - First authorized attempt to cure a human genetic disorder by gene transfer.

1999 - A young French girl was cured of an inherited immune disorder when cells from her bone marrow were removed, modified in the laboratory, and then placed back in her body.

The patient above is 18 yrs. old and has been receiving monthly blood transfusions since the age of 3 because of a genetic disorder he has. An international team of scientists have managed to partially correct his genetic faults, granting him his independence from the blood transfusions. He hasn’t needed a transfusion at all during the last 21 months!

Gene Therapy: Using Viruses

Viruses are often used because of their ability to enter a cell's DNA.

1. The virus particles are modified so that they cannot cause disease.

2. Then, a DNA fragment containing a replacement gene is spliced to viral DNA.

3. The patient is then infected with the modified virus particles, which should carry the gene into cells to correct genetic defects.

Other Genetic Testing Methods: DNA Fingerprinting

DNA Fingerprinting - Analysis of sections of DNA that have little or no known function, but vary widely from one individual to another, in order to identify individuals. Does not analyze the cell's most important genes

because they are largely identical among most people.

Samples can be obtained from blood, sperm, and even hair strands with tissue at the base.

Used in Forensic Science: Has helped convict criminals as well as overturn many convictions

Used to determine paternity

Gene Therapy- A Promising Cure? Unfortunately, gene therapy experiments have not

always been successful. Attempts to treat cystic fibrosis by spraying genetically

engineered viruses into the breathing passages have not produced a lasting cure.

For all the promise it holds, in most cases gene therapy remains a high-risk, experimental procedure.

Genetic Engineering

Genetic Variation

You can compare dogs of every breed imaginable!

There is an enormous range of characteristics that are the result of genetic variation.

The differences among breeds of dogs are so great that someone might think that many of these breeds are different species.

They're not, of course, but where did such differences come from?

Selective Breeding The answer, of course, is that we did it.

Humans have kept and bred dogs for thousands of years, always looking to produce animals that might be better hunters, better retrievers, or better companions.

By selective breeding, allowing only those animals with desired characteristics to produce the next generation, humans have produced many different breeds of dogs.

Selective Breeding

Humans use selective breeding, which takes advantage of naturally occurring genetic variation in plants, animals, and other organisms, to pass desired traits on to the next generation of organisms. Nearly all domestic animals—including horses,

cats, and farm animals—and most crop plants have been produced by selective breeding.

Selective Breeding

The ancestor of modern corn had tiny kernels, each protected by a tough husk.

Domestication of maize, which began thousands of years ago, selected for large sheathed cobs containing large kernels without husks.

Hybridization

Hybridization - Breeding technique that involves crossing dissimilar individuals to bring together the best traits of both organisms.Hybrids, the individuals produced by such

crosses, are often hardier than either of the parents.

Zeedonk - Zebra and Donkey Liger – Lion and Tiger

Jaglion- Jaguar and Lion

Inbreeding To maintain the desired characteristics

of a line of organisms, breeders often use a technique known as inbreeding.

Inbreeding is the continued breeding of individuals with similar characteristics.

The many breeds of dogs—from beagles to poodles—are maintained by inbreeding. Inbreeding helps to ensure that the characteristics that make each breed unique will be preserved.

Risks of Inbreeding Although inbreeding is useful in retaining a certain set

of characteristics, it does have its risks. Most of the members of a breed are genetically similar. Because of this, there is always a chance that a cross

between two individuals will bring together two recessive alleles for a genetic defect.

Serious problems in many breeds of dogs, including blindness and joint deformities in German shepherds and golden retrievers, have resulted from excessive inbreeding.

Increasing Variation

Selective breeding would be nearly impossible without the wide variation that is found in natural populations.

This is one of the reasons biologists are interested in preserving the diversity of plants and animals in the wild.

However, sometimes breeders want more variation than exists in nature.  

Breeders can increase the genetic variation in a population by inducing mutations, which are the ultimate source of genetic variability.

Increasing Variation As you may recall, mutations are inheritable changes in

DNA. Mutations occur spontaneously, but breeders can

increase the mutation rate by using radiation and chemicals.

Many mutations are harmful to the organism. With luck and perseverance, however, breeders can

produce a few mutants—individuals with mutations—with desirable characteristics that are not found in the original population.

Producing New Kinds of Plants

Drugs that prevent chromosomal separation during meiosis have been particularly useful in plant breeding.

Sometimes these drugs produce cells that have double or triple the normal number of chromosomes.

Plants grown from such cells are called polyploid because they have many sets of chromosomes.

Polyploidy: the condition of having three, four, or more sets of chromosomes instead of the two present in diploids.

Polyploidy

Polyploidy is usually fatal in animals. However, for reasons that are not clear, plants are

much better at tolerating extra sets of chromosomes. Polyploidy may instantly produce new species of plants

that are often larger and stronger than their diploid relatives.

Genetic Engineering

Genetic Engineering - Process of making changes in the DNA code of living organisms.

Recombinant DNA

Recombinant DNA - DNA produced by combining DNA from different sources. Can join “synthetic” sequences to

“natural” ones using enzymes that splice DNA together.

Is possible to take a gene from one organism and attach it to the DNA of another organism by using enzymes.

Bacteria Transformation Plasmid - Circular DNA molecule found in

bacteria. Plasmids are found naturally in some

bacteria and are useful for DNA transfer. Why?

1. It’s DNA sequence promote plasmid replication. Ensures the transformed bacteria will

be replicated.

2. Plasmids contain a genetic marker —a gene that makes it possible to distinguish bacteria that carry the plasmid and the foreign DNA from those that don't.

Bacteria Transformation

Is it Possible to Transfer Whole Genes From One Organism to Another?

In 1986, American researcher Steven Howell transferred the gene for luciferase into tobacco plant cells. Luciferase is an enzyme that

allows fireflies to glow. The plants glowed in the dark!

Transgenic Organisms

Transgenic - Term used to refer to an organism that contains genes from other organisms.

1. Transgenic BacteriaReproduce rapidly and are easy to grow.Produce a host of important substances such as insulin,

growth hormone, and clotting factor which are used to treat serious human diseases and conditions.

Oil eating bacteria help clean up oil spillsBacteria transformed with the genes for human

proteins now produce these important compounds cheaply and in great abundance.

Transgenic Organisms

2. Transgenic Animals Used to study genes and to improve the food supply.

Mice have been produced with human genes that make their immune systems act similarly to those of humans.

Allows scientists to study the effects of diseases on the human immune system.

Some transgenic livestock now have extra copies of growth hormone genes.

Grow faster and produce leaner meat

Transgenic Organisms

3. Transgenic Plants Are now an important part of our food supply.

In the year 2000, 52% of the soybeans and 25% of the corn grown in the US were transgenic, or genetically modified (GM).

Some GM plants contain genes that produce a natural insecticide. The crops do not have to be sprayed with synthetic

pesticides. Other crop plants have genes that enable them to resist weed-

killing chemicals. Allows crops to survive while weeds are still controlled.

Cloning

Clone - Member of a population of genetically identical organisms produced from a single cell.

Cloned colonies of bacteria and other microorganisms are easy to grow, but this is not always true of multicellular organisms, especially animals.

Cloning Animals

In 1997, Scottish scientist Ian Wilmut stunned biologists by announcing that he had cloned a sheep, which he later named Dolly.

How did he do it?

1. Take the nucleus of any female’s egg cell and remove it.

2. This cell is fused with a somatic body cell (this is the cell you want to make a clone of) taken from another adult.

3. The fused cell is tricked into thinking its fertilized and begins to divide.

4. The embryo is then placed in the reproductive system of a foster surrogate mother, where it develops normally.

Cloning Cloned cows, pigs, mice, and other mammals have been

produced by similar techniques. Researchers hope that cloning will enable them to make copies

of transgenic animals and even help save endangered species. On the other hand, the technology is controversial for many

reasons, including studies suggesting that cloned animals may suffer from a number of genetic defects and health problems.

The use of cloning technology on humans, while scientifically possible, raises serious ethical and moral issues that have caused many people to oppose such work. As techniques improve, these important issues will become even more pressing.

Clone

Member of a population of

genetically identical organisms produced

from a single cell.

CC with surrogate mom

Genetic mom

CC = Copy Cat (the clone)

CC gives birth to 3 healthy kittens

Online Cloning Lab Due Tuesday, 12/8