Genetics

1. Genetics Karyotypes, Disorders, and Genetic Engineering

2. Essential Question • What are Chromosomes? • How do chromosomal abnormalities create disorders?

3. Karyotype • Karyotype picture of chromosomes arranged together in pairs. • To make a karyotype scientists take pictures of cells going through mitosis. They cut the photographs and group the chromosomes in pairs

4. Karyotype • 46 chromosomes in diploid human cell • 23 chromosomes in a haploid sperm or egg • Autosomes pairs 1-22 • Sex chromosomes pair 23 • Biologist will write 46XX female and 46XY male

6. Disorders • Cystic Fibrosis • Usually fatal found on chromosome 7 (recessive allele) • Serious digestive problems and heavy mucus that clogs their lungs and breathing passageways • Cause deletion of 3 bases in the middle of a sequence for a protein • About half of the children survive into their 20’s

7. Disorders • Sickle Cell Disease • Cells bent and twisted shape • Cells more rigid than normal • Get caught in the capillaries as a result blood flow stops moving through these vessels, damaging cells and tissues • Abnormal hemoglobin (protein carries oxygen)

8. Disorders • Because abnormal hemoglobin the cell carries less oxygen causing hemoglobin to stick together causing shape • African Americans carry the sickle cell b/c ancestry to West Africa heterozygous resistant to Malaria

9. Chromosomal Disorders • Nondisjunction error in meiosis when homologous chromosomes fail to separate • If nondisjunction occurs abnormal numbers of chromosomes may find their way into gametes

10. Chromosomal Disorders • Down Syndrome • Trisomy an individual will have three copies of a chromosome • Most common Trisomy 21 Down syndrome 1 in 800 babies are born with Down Syndrome produces mild to severe mental retardation

11. Sex Chromosome Disorders Turner’s syndrome nondisjunction in females inherit only one X chromosome Women usually sterile and sex organs do not develop at puberty Klinefelter’s syndrome nondisjunction in males inherit an extra X chromosome Usually prevents individual from reproducing No cases of NO X meaning it is essential for normal development

12. Testing • Genetic tests use labeled DNA probes to detect specific sequences found in disease-causing alleles. • Some tests look at changes in the lengths of normal and abnormal alleles

13. Testing • 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 • This works because the human genome ensures that no individual is exactly like any other

14. Genetic Testing • amniocentesis, can be used beginning at the 14th to 16th week of pregnancy to assess the presence of a specific disease. • Fetal cells extracted from amniotic fluid are cultured and karyotyped to identify some disorders.

15. chorionic villus sampling (CVS) can allow faster karyotyping and can be performed as early as the eighth to tenth week of pregnancy. • This technique extracts a sample of fetal tissue from the chorionic villi of the placenta.

16. Testing • Gene Therapy process of changing the gene that causes a genetic disorder

17. Can anyone remember when we didn’t have… • Video games • Personal computers • Cell phones • Microwaves

18. How about… • Antibiotics (1937) • Artificial insemination in cattle (1950’s) • Human-grade insulin (about 1980) • Herbicide resistant soybeans introduced (1995) • Dolly the sheep is cloned (1997) • Spinal cord repair (???)

19. Biotechnology has been around for a long time • People invented winemaking about 10,000 years ago. • Followed by ensiling (like composting). • Then meat preservation. • And genetic selection.

20. Selective Breeding • Breeding only those animals with desired characteristics to produce the next generation. • Ex: The many different breeds of dogs displayed at a dog show are produced by humans.

21. Increasing Variation • Breeders can increase variation in a population by inducing mutations, which are the ultimate source of genetic variability. • Mutation- Inheritable changes in DNA that occur spontaneously.

22. Breeders can increase the mutation rate with radiation and chemicals. • Many are harmful. • Once in a while can produce a few mutants (individuals with desirable characteristics that are not found in the original population.)

23. Can also be used to produce new kinds of bacteria that can be helpful. • Ex: The bacteria that clean up oil spills.

24. Genetic Engineering • Genetic Engineering making changes in the DNA code of living organism • Years ago scientists used chance to breed plants and animals • Today scientists use their knowledge of the DNA and its chemical properties to study and change DNA molecules

25. Genetic Engineering • In order for scientist to change DNA they must be able to extract DNA • The first step is to cut the DNA with a restriction enzyme • Second step is Separating the DNA through a process called gel electrophoresis • http://www.phschool.com/webcodes10/index.cfm?fuseaction=home.gotoWebCode&wcprefix=cbe&wcsuffix=4132

26. Gel Electrophoresis • DNA is a negatively charged molecule. • The smaller the DNA fragment, the faster and farther it moves across the gel toward the positive end. • Can be used to compare the DNA of different organisms or individuals.

27. Bacteria Transformation • A cell takes in DNA from outside the cell. This external DNA becomes part of the cell’s DNA. • Plasmids, tiny circles of DNA in bacteria, are used to copy other DNA.

28. Genetic Engineering • Once the DNA is in manageable form its sequence can be read • Then scientist use recombinant DNA enzymes make it possible to take a gene from one organism and attach it to the DNA of another organism Video Clip • Then PCR or polymerase chain reaction is used to make copies of DNA

29. Genetic Engineering • The previous steps show how scientists get the genetic information and where changes can be made.

30. Genetic Engineering • Once scientist have the genetically modified DNA they use a process of transformation to get the DNA into the cell • Scientists use a bacterium that produces tumors in plants to introduce the new DNA • Scientist inactivate the tumor producing gene and insert the foreign DNA • The DNA is transformed into the plant cell

31. Genetic Engineering • In animal cells scientists will inject the cell with the DNA. Once inside the nucleus, enzymes normally responsible for DNA repair and recombination may help insert the foreign DNA • Or DNA might be “knocked out” of the way and the foreign DNA inserted in its place

32. Genetic Engineering • Transgenic Organisms • Transgenic an organism that contains genes from other organisms • Genetic engineering has brought about the growth of biotechnology • We now have Transgenic microorganisms, animals, plants

33. Genetic Engineering • Transgenic bacteria are used to produce insulin, growth hormone, and clotting factor • Transgenic animals are used to study genes and improve food supply • Livestock will be given extra copies of growth hormone which means faster growth, more meat and less fat

34. Genetic Engineering • Transgenic plants are important part of our food supply • Many plants have a natural insecticide so crops do not need to be sprayed and some resist weed killing chemicals.

35. Transgenic Organisms • Organisms that contain genes from other organisms. Example: • Bt Corn: contains a gene from bacteria that kills the Lepidoptera larvae AND resists weed killer.

36. Important Regulatory Issues • Regulatory policy • Ecological issues - genes can move to non-target species. Once the genes are out of the bottle, there is no bringing them back. • Ethical issues - what about using embryos for research? • Scientist will do the research - every one else must develop the guidelines. • Making regulations for biotechnology is brand new territory. We have to get it right.

37. What is Bt Corn? • This is a transgenic organism • Gene isolated from a bacterium Bacillus thuringiensis, (resists the European corn borer), and inserted into corn. • Bt corn produces a unique protein which is toxic to the corn borer. • This reduces to need to apply conventional pesticides.

38. Is Bt corn harmful to non-target insects? • Cornell study: Monarch larvae that eat Bt corn pollen get sick or die • National Academy of Sciences (2001): Yes, some effects even under field conditions. • Penn State scientists: There is an effect, but larvae develop before and after pollen shedding, so it’s not a huge deal. • Is this important?

39. What are Roundup Ready Corn and Soybeans? • Plant the seed. Wait for crop and weeds to germinate. • Then spray Roundup. It will kill the weeds but not the crop. • Reduces need for pre-emergence (and sometimes post-emergence) herbicides. • About 80% of soybeans used are Roundup Ready.

40. Genetic Engineering • Cloning • Clone is a member of a population of genetically identical cells produced from a single cell • Ian Wilmut in 1997 cloned a sheep called Dolly • The nucleus of an egg cell is removed, then a cell is fused with a cell taken from another adult. The egg begins to divide.

41. Another application - stem cell research • Stem cells found in the embryo (blastocyst). They’re waiting for a signal to develop into an organ or tissue. • Stem cells also found in liver, brain, and bone marrow. • Stem cell research: • Usually uses embryonic stem cells • In the US, not permitted to use surplus human embryos from in vitro fertilization - this destroys the embryo • When we unravel the signal process, we hope to generate organs or repair spinal cord injuries

42. Biotechnical advances in the 20th century • Antibiotics • Artificial insemination • Embryo transfer • Production of insulin and other products via recombinant techniques

43. Medical Advances a Few Years Away • Make new organ replacements for transplant patients. • Repair spinal cord injuries. • Gene therapy - knock out the bad gene and insert a good one in its place. • Diabetes - 16 million • Cystic fibrosis - 200,000? • Schizophrenia - 2 million