1. Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Memmler’s The Human Body in Health and Disease 11 th edition Chapter 25 Heredity and Hereditary Diseases

2. Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Methodical Investigation into Heredity How traits are transmitted from parents to offspring 19th century Gregor Mendel Genes (units of heredity)

3. Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Genes and Chromosomes Genes are DNA segments Thousands of genes per chromosome Gene carries code for specific trait Cell contains 46 chromosomes (except sex cell) –1 pair sex chromosomes –22 pairs autosomes Allele—Any form of gene on a specific cite on a chromosome Alleles for each trait exist in pairs

4. Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Checkpoint 25-1: What is a gene and what is a gene made of?

5. Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Dominant and Recessive Genes Dominant gene –Always expresses effect –Need from one parent only Recessive gene –No effect unless paired allele also recessive –Need from both parents Heterozygous alleles Homozygous alleles

6. Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Dominant and Recessive Genes (cont’d) Phenotype – and characteristic that can be observed. –Example: eye color, blood type Genotype – a person’s genetic makeup –Example: heterozygous dominant

7. Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Checkpoint 25-2: What is the difference between a dominant and a recessive gene?

8. Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Question: Paired genes for a given trait are called: a. chromosomes b. gametes c. alleles

9. Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Answer: c. alleles

10. Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Distribution of Chromosomes to Offspring Meiosis –Produces gametes with 23 chromosomes –Cells receive chromosomes at random from parents Punnett square

11. Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Checkpoint 25-3: What is the process of cell division that forms the gametes?

12. Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Question: True or False?: Genotype is all the characteristics of a person (or an organism) that can be seen or tested for.

13. Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Answer: False: Phenotype is all the characteristics of a person (or an organism) that can be seen or tested for.

14. Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Sex Determination Sex chromosomes not matched in size, appearance Female (X) chromosome larger Male (Y) chromosome smaller Females—two X chromosomes Males—X, Y chromosomes Sperm—X or Y chromosome, determines offspring sex

15. Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Sex determination. If an X chromosome from a male unites with an X chromosome from a female, the child is female (XX); if a Y chromosome from a male unites with an X chromosome from a female, the child is male (XY).

16. Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Sex-Linked Traits Traits carried on sex chromosomes Most are carried on X (X-linked) Appear almost exclusively in males

17. Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Checkpoint 25-4: What sex chromosome combination determines a female? A male? Checkpoint 25-5: What term is used to describe a trait carried on a sex chromosome?

18. Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Hereditary Traits Determined by single pair of genes –Less common Determined by gene pairs acting together –More common –Multifactorial inheritance

19. Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Gene Expression Gene effects on phenotype are influenced by many factors Sex Presence of other genes Environment

20. Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Genetic Mutation Genes or chromosomes that do not replicate exactly Changes in genes or chromosomes Chromosomal breakage or loss, gene fragment rearrangement May occur during cell division –Spontaneous –Induced by mutagen

21. Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Checkpoint 25-6: What is a mutation?

22. Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Genetic Diseases Gene disorders All are genetic Some are hereditary –Passed from parent to offspring –Genetic research can identify some causes

23. Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Congenital Versus Hereditary Diseases Congenital Present at birth Possible causes –Maternal infections –Environmental toxins –Maternal alcohol (fetal alcohol syndrome), smoking –Maternal nutrition Hereditary Genetically transmitted or transmissible Not always evident at birth

24. Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Checkpoint 25-7: Can a disorder be congenital but not hereditary? Explain.

25. Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Examples of Genetic Diseases Down syndrome (trisomy 21) Huntington disease Marfan syndrome Phenylketonuria (PKU) Sickle cell disease Cystic fibrosis Tay-Sachs disease Progressive muscular atrophies Albinism Osteogenesis imperfecta Neurofibromatosis Fragile X syndrome Some cancers

26. Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Checkpoint 25-8: What causes phenylketonuria?

27. Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Treatment and Prevention of Genetic Diseases More than 400 genetic diseases identified List is growing as science advances

28. Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Genetic Counseling Family history (pedigree) Laboratory studies –Amniocentesis –Chorionic villus sampling (CVS) –Karyotype analysis Counseling prospective parents

29. Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Amniocentesis. A sample of amniotic fluid is removed from the amniotic sac. Cells and fluid are tested for fetal abnormalities. (Reprinted with permission from Cohen BJ. Medical Terminology. 4th ed. Philadelphia: Lippincott Williams & Wilkins, 2004.)

30. Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Checkpoint 25-9: What is a pedigree and how is a pedigree used in genetic counseling? Checkpoint 25-10: What is a karyotype?

31. Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Question: Which of these is the noninvasive method for testing for genetic disease? a. amniocentesis b. chorionic villus sampling c. karyotype analysis

32. Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Answer: c. karyotype analysis

33. Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins Progress in Medical Treatment Some diseases respond to early diagnosis and treatment Dietary control –Maple syrup urine disease –Wilson disease (+ drug therapy) –PKU Drug therapy Hormone therapy –Klinefelter syndrome (+psychotherapy) Psychotherapy

34. Copyright © 2009 Wolters Kluwer Health | Lippincott Williams & Wilkins End of Presentation