Mendelian Inheritance Part 2

1. Mendelian InheritancePart 2 BIO 2215 Oklahoma City Community College Dennis Anderson

2. Multiple Alleles • More than two forms of an allele exist in a population • An individual only has two of the alleles

3. Multiple Blood Alleles A allele for making the A antigen on red blood cells B allele for making the B antigen on red blood cells O allele for NOT making the A or B antigen on red blood cells

4. Three alleles give four blood types AA or AO = Type A blood BB or BO = Type B blood AB = Type AB blood OO = Type O blood

5. California Court Case • 1946 the California supreme court ruled that Charlie Chaplin was the biological father of a child he claimed was not his. • His defense was that the baby had type B blood. He had type A and the woman who sued him had type O (These may not be the actual blood types, but it illustrates the point) • Was the court correct?

6. AA, AO = Type A BB, BO = Type B AB = Type AB OO = Type O AO AO OO OO O O A O The judge should take a course in zoology!

7. Mutation • Change in a gene • nucleotide sequence is often altered • Produce abnormal protein • Cause a disease (sickle cell anemia) • Resistance to a disease (AIDS)

8. Levels of Mutation • Molecular level • Deletion of nucleotides • Addition of nucleotides • Substitution of nucleotides • Chromosomal level • Change in structure • Change in number of chromosomes

9. Mutant Has different phenotype because of a change in his DNA Normal Mutant • Unusual phenotype • Mutations cause mutants

10. Hemoglobin • Protein molecule made of 4 globin chains • 2 alpha chains with 141 amino acids • 2 beta chains with 146 amino acids

11. Sickle Cell Anemia • Gene for making hemoglobin is changed from normal

12. Valine Valine Histidine Histidine Glutamic acid Valine Leucine Proline Proline Leucine Thre.. Thre.. CAC One nucleotide has changed Normal Hemoglobin Beta ChainFirst six amino acids CTC Hemoglobin S Beta ChainFirst six amino acids

13. Hemoglobin S • Forms long rod like molecules that stretch RBC into a sickle shape • Sickled cells obstruct circulation of blood • Allele for hemoglobin S is recessive • SS = Normal • Ss = Carrier • ss = Sickle cell anemia

14. Why is the s allele more common in Blacks than Whites? • Ancestors of Blacks lived in areas where malaria was present • Malaria parasite cannot survive on hemoglobin S • Even Ss are immune to malaria • The s allele is beneficial in an environment where malaria is present

15. Beta Globin Mutations • Over 300 different mutations!

16. Causes of Mutations • Spontaneous • Random • About 1/100,000 chance of a gene mutating • Induced • Caused by mutagens • X-rays…break DNA • UV radiation….Thymine dimers • LSD…Break chromosomes • Cigarette smoke…damages tumor suppressor genes

17. Spontaneous Mutation • Two people of normal height have a child with dwarfism • Bacteria become resistant to antibiotics • Cold virus mutates every year • Immunity for this years cold will not protect you from next years cold • AIDS virus mutates too fast to make a conventional vaccine

18. A C A T T G T C A C A G T C T T Ultraviolet LightCauses adjacent Thymines to bond together

19. A C A G T C T T Excision Repair EnzymeRemoves small section of DNA

20. DNA Polymerase fills in missing nucleotides A C A T T G T C Excision RepairRemoves small section of DNA A C T C

21. Xeroderma Pigmentosum • Skin blisters from sun exposure • Develop skin cancer as children • Recessive gene does not produce DNA repair enzyme

22. Sunlight Exposure Increases the Risk of Skin Cancer • DNA repair enzymes do not always fix the damage that sunlight inflicts on DNA of skin cells. • The more a person is exposed to sunlight, the greater the risk of skin cancer

23. Homologous chromosomes line up in a double file in metaphase I of meiosis

24. Homologous Pairs Separate

25. Four Gametes With Single Chromosomes

26. Fertilization

27. Nondisjunction One pair of chromosomes fails to separate during meiosis

28. Trisomy Zygote ends up with 3 chromosomes instead of 2 for a given chromosome pair.

29. Karyotype • Picture of chromosomes • Often arranged with autosomes in descending order and sex chromosomes separate

30. Normal Male

31. Normal Female

32. Trisomy 21Down Syndrome

33. Down Syndrome • Large tongue • Flat face • Single crease across palm • Slanted eyes • Mental retardation • Some are not

34. Maternal Age & Down Syndrome

35. Trisomy 18Edward Syndrome

36. Edward Syndrome • Heart defects • Displaced liver • Abnormal hands • Low-set ears • Severe retardation • 98% abort • Lifespan < 1 year

37. Trisomy 13Patau Syndrome

38. Patau Syndrome • Cleft lip and palate • Extra fingers & toes • polydactylism • Defects • Heart • Brain • Kidney • Most abort • Live span < 1 month

39. Klinefelter Syndrome

40. Klinefelter Syndrome • Breast development • Small testes • Sterile • Low intelligence • Not retarded Klinefelter Website

41. Turner Syndrome

42. Turner Syndrome • Short • Not go through pruberty • Produce little estrogen • Sterile • Extra skin on neck

43. Abnormal Chromosome Numbers • Aneuploidy • Missing or extra chromosome • Polyploidy • Extra set of chromosomes • Usually lethal • Common in cancer • Common in plants

44. Fetal testing can determine abnormal karyotypes

45. The End