Genetic Engineering

Think of the possibilities Video

Selective Breeding Selective Breeding Selective breeding allows only those organisms with desired characteristics to produce the next generation. Nearly all domestic animals and most crop plants have been produced by selective breeding. Example: Champion race horses, cows with tender meat, large oranges on a tree.

Selective Breeding Artificial selection- where individuals with desirable traits are mated to produce offspring with those traits. Hybridization  Hybridization is the crossing of dissimilar individuals to bring together the best of both organisms. Hybrids, the individuals produced by such crosses, are often hardier than either of the parents.

Inbreeding   Inbreeding is the continued breeding of individuals with similar characteristics. Inbreeding helps to ensure that the characteristics that make each breed unique will be preserved. Serious genetic problems can result from excessive inbreeding. WHY?

Inbreeding and Variation Recessive genetic disorders can be blindness, or joint deformities. Variation is a term used to identify the difference between individuals of a species. For example: Some humans have blond hair and some have brown. This is a variation among humans. Finches-

Increasing Variation Why might breeders try to induce mutations? Breeders increase the genetic variation in a population by inducing mutations. Producing New Kinds of Bacteria Introducing mutations has allowed scientists to develop hundreds of useful bacterial strains, including bacteria that can clean up oil spills.

Genetics Engineering In genetic engineering, biologists make changes in the DNA code of a living organism. How do scientists make changes to DNA? Scientists use different techniques to: extract DNA from cells cut DNA into smaller pieces identify the sequence of bases in a DNA molecule make unlimited copies of DNA

The Tools of Molecular Biology Each restriction enzyme cuts DNA at a specific sequence of nucleotides. Molecular biologists have developed different techniques that allow them to study and change DNA molecules. Restriction enzymes cut DNA at specific sequences. This drawing shows how restriction enzymes are used to edit DNA. The restriction enzyme EcoR I, for example, finds the sequence CTTAAG on DNA. Then, the enzyme cuts the molecule at each occurrence of CTTAAG. The cut ends are called sticky ends because they may “stick” to complementary base sequences by means of hydrogen bonds.

How do scientists manipulate DNA 1. DNA is removed from the cell of an organism 2. DNA is cut using restriction enzymes to identify the bases. 3. There are thousands of restriction enzymes, each cuts the DNA at a different starting place based in the nucleotide sequence.

4. DNA fragments are separated by gel electrophoresis. 5. Positive charged DNA moves to negative poles and negative DNA moves to positive poles. Smaller fragments move faster, larger move slower. 6. This is also how DNA is compared (ex at crime scenes) 7. Then, unlimited copies of fragments are made by scientist. Nova: who done it http://www.pbs.org/wgbh/nova/sheppard/analyze.html Video clip Video clip 2

http://www.dnalc.org/resources/animations/restriction.html

Cell Transformation

13-3 Cell Transformation Recombinant DNA Host Cell DNA Target gene Modified Host Cell DNA

Cell Transformation During transformation, a cell takes in DNA from outside the cell. The external DNA becomes a component of the cell's DNA. Foreign DNA is first joined to a small, circular DNA molecule known as a plasmid. Plasmids are found naturally in some bacteria and have been very useful for DNA transfer. The plasmid has 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.

Biotechnology and genetic engineering Genetic engineering is making changes in the DNA code of a living organism. A scientist can take genes from one organism and transfer them to another organism. This is called transformation. Genetic engineering has given rise to a new technological field called biotechnology (technology of life). The organisms that have DNA transferred to them are called transgenic. (trans: means different, genic: refers to genes)

Transgenic helpful? How are transgenic organisms useful to human beings? Transgenic bacteria produce important substances useful for health and industry. Transgenic bacteria have been used to produce: insulin growth hormone clotting factor

Gene for human growth hormone Recombinant DNA DNA recombination Human Cell Bacterial chromosome Sticky ends DNA insertion Bacteria cell During transformation, a cell incorporates DNA from outside the cell into its own DNA. One way to use bacteria to produce human growth hormone is to insert a human gene into bacterial DNA. The new combination of genes is then returned to a bacterial cell. The bacterial cell containing the gene replicates over and over. Bacteria cell containing gene for human growth hormone Plasmid Copyright Pearson Prentice Hall

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Animals and plants Transgenic animals: genes inserted into animals so they produce what humans need. A way to improve the food supply: livestock given genes that make them grow faster or resist bacteria that cause infections. Mice are given human genes that make their immune system work like ours. They can now be used for researching the human immune system

Transgenic Plants Transgenic plants: plants are given genes that make them produce a natural pesticide. Now they don’t have to be sprayed with cancer causing pesticides. 25% of all corn is like this. It called genetically modified or GM.

Cloning

Cloning A clone is a member of a population of genetically identical cells produced from a single cell. In 1997, Ian Wilmut cloned a sheep called Dolly. Dolly and Bonnie The adult sheep is Dolly, the first mammal cloned from an adult cell. The lamb is Dolly’s first offspring, called Bonnie. The fact that Dolly was cloned did not affect her ability to produce a live offspring. Photo Credit: PA News

Cloning Donor Nucleus Fused cell Egg Cell Embryo Cloned Lamb In early 1997, Dolly made headlines as the first clone of an adult mammal.  Embryo Cloned Lamb Foster Mother

Cloning A single cell is removed from a parent organism. An entire individual is grown from that cell. Remember one cell has all the DNA it needs to make an entire organism. Each cell in the body has the same DNA, but cells vary because different genes are turned on in each cell.

Dolly Dolly was the first animal cloned. She had the same exact DNA as her mother and had no father. Cloning is a form of asexual reproduction. Since Dolly, cats and other organisms have been cloned. The cat that was cloned had the same exact DNA but different color fur than the mother. How can this be? Environment plays a huge part in the way organisms develop. http://content.tutorvista.com/biology_11/content/media/cloning.swf

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Cool cloning vids http://videos.howstuffworks.com/discovery/38036-discovery-news-tech-human-cloning-video.htm http://videos.howstuffworks.com/tlc/29324-understanding-cloning-a-cow-video.htm http://videos.howstuffworks.com/tlc/29134-understanding-saving-endangered-species-with-cloning-video.htm http://videos.howstuffworks.com/science-channel/39069-popscis-future-of-organ-factory-video.htm

Human Genome

Human Chromosomes Human Chromosomes Cell biologists analyze chromosomes by looking at karyotypes. Cells are photographed during mitosis. Scientists then cut out the chromosomes from the photographs and group them together in pairs. A picture of chromosomes arranged in this way is known as a karyotype.

Human Karyotype

Human Traits Pedigree Charts A pedigree chart shows the relationships within a famliy. Genetic counselors analyze pedigree charts to infer the genotypes of family members.

Human Traits A horizontal line connecting a male and a female represents a marriage. A square represents a male. A circle represents a female. A vertical line and a bracket connect the parents to their children. A circle or square that is not shaded indicates that a person does not express the trait. A shaded circle or square indicates that a person expresses the trait. This drawing shows what the symbols in a pedigree represent.

Human Genes Blood Group Genes Human blood comes in a variety of genetically determined blood groups. A number of genes are responsible for human blood groups.

Human Genes Recessive Alleles Many disorders are caused by autosomal recessive alleles.

Human Genes This table shows the major symptoms of some well-known genetic disorders. Copyright Pearson Prentice Hall

From Gene to Molecule Sickle Cell Disease Sickle cell disease is a common genetic disorder found in African Americans. It is characterized by the bent and twisted shape of the red blood cells. These red blood cells contain the abnormal hemoglobin characteristic of sickle cell disease. Photo credit: ©Omikron/Photo Researchers, Inc.

Sex-Linked Genes Sex-Linked Genes The X chromosome and the Y chromosomes determine sex. Genes located on these chromosomes are called sex-linked genes. More than 100 sex-linked genetic disorders have now been mapped to the X chromosome.

Sex-Linked Genes The Y chromosome is much smaller than the X chromosome and appears to contain only a few genes.

Sex-Linked Genes For a recessive allele to be expressed in females, there must be two copies of the allele, one on each of the two X chromosomes. Males have just one X chromosome. Thus, all X-linked alleles are expressed in males, even if they are recessive.

Chromosomal Disorders The most common error in meiosis occurs when homologous chromosomes fail to separate. This is known as nondisjunction, which means, “not coming apart.” If nondisjunction occurs, abnormal numbers of chromosomes may find their way into gametes, and a disorder of chromosome numbers may result.

Chromosomal Disorders Down syndrome produces mild to severe mental retardation. It is characterized by: increased susceptibility to many diseases higher frequency of some birth defects Down Syndrome Karyotype This karyotype is from a person with Down syndrome. Down syndrome causes mental retardation and various physical problems. People with Down syndrome can, however, lead active, happy lives. Photo credit: ©Dr. Dennis Kunkel/CNRI/Phototake

The Human Genome Project A genome is all the DNA in one cell of an organism. The main goal of the Human Genome Project was to identify the DNA sequence of every gene in the human genome. It was completed in May 2006. Scientists estimate that human DNA has around 25,000 genes.

Gene Therapy In gene therapy, an absent or faulty gene is replaced by a normal, working gene. The body can then make the correct protein or enzyme, eliminating the cause of the disorder.

Gene Therapy Viruses are often used because of their ability to enter a cell’s DNA. Virus particles are modified so that they cannot cause disease. Gene therapy is the process of changing the genes that cause a genetic disorder. This drawing shows how a virus might be used to deliver the gene for normal hemoglobin into a person’s bone marrow. Copyright Pearson Prentice Hall

Gene Therapy A DNA fragment containing a replacement gene is spliced to viral DNA. Gene therapy is the process of changing the genes that cause a genetic disorder. This drawing shows how a virus might be used to deliver the gene for normal hemoglobin into a person’s bone marrow. Copyright Pearson Prentice Hall