Chapter 2 Heredity and Conception

1. Chapter 2Heredity and Conception

2. Heredity and Conception: Truth or Fiction? • Your father determined whether you are female or male. • Brown eyes are dominant over blue eyes.

3. Heredity and Conception: Truth or Fiction? • You can carry the genes for a deadly illness and not become sick yourself. • Identical twins are more likely than fraternal twins to share disorders such as schizophrenia and vulnerability to alcoholism.

4. Heredity and Conception: Truth or Fiction? • 120 to 150 boys are conceived for every 100 girls. • Sperm travel about at random inside the woman’s reproductive tract, so that reaching the ovum is a matter of luck.

5. Heredity and Conception: Truth or Fiction? • Extensive athletic activity may contribute to infertility in the male. • “Test-tube” babies are grown in a laboratory dish throughout their nine-month gestation period.

6. Heredity and Conception: Truth or Fiction? • You can select the sex of your child.

7. The Influence of Heredity on Development The Nature of Nature

8. What Is Meant by Heredity? • Heredity • Defines one’s nature • Genetics • Field within the science of biology that studies heredity • Genetic influences • Physical traits • Behavioral traits • Psychological disorders

9. What Are Chromosomes and Genes? • Chromosomes • Found in cells • 23 pairs of rod-like structures • Genes • Segments within chromosomes • Regulate development of traits • DNA • Large strands make up genes • Double spiral (helix) • Composed of phosphate (P), sugars (S), and base pairs

10. Figure 2.1 Cells, Chromosomes, and DNA

11. What Happens During Cell Division? • Mitosis • Cell division by which growth occurs • Strands of DNA break apart and are rebuilt • Result is identical copies of DNA strand

12. Figure 2.2 Mitosis

13. What Happens During Cell Division? • Meiosis • Cell division by which sperm and ova are produced • 23 chromosome pairs divide • Result is new cell with only 23 chromosomes • 23 pairs are autosomes • 23rd pair determines gender; X from mother and X or Y from father

14. How Are Twins Formed? • Monozygotic Twins (MX) • Derived from a single zygote that has split in two • Genetically identical • Dizygotic Twins (DZ) • Derived from two zygotes • Share 50% of genetic material

15. How Do Genes Determine Traits? • Traits are determined by alleles • Pair of genes • Homozygous • Alleles for a trait are the same • Heterozygous • Alleles for a trait are different

16. Dominant and Recessive Traits: Mendel’s Laws of Heredity • Averaging • Effects of both alleles are shown • Incomplete dominance and codominance • Law of Dominance • Dominant allele paired with recessive allele • Dominant allele appears in child

17. Figure 2.4 Transmission of Dominant and Recessive Traits

18. Table 2.1

19. Chromosomal Abnormalities: Down Syndrome • Cause: extra chromosome on 21st pair • Probability increases with increased age of parent • Characteristics of children • Facial features • Cognitive and physical deficiencies • Adjustment of children

20. Table 2.2

21. Chromosomal Abnormalities: Sex Linked • Male with extra sex chromosome • XYY - extra Y chromosome • XXY - Klinefelter syndrome • Female with abnormal number of sex chromosomes • X - Turner syndrome • XXX - Triple X syndrome

22. Genetic Abnormalities • Recessive gene abnormalities • PKU (phenylketonuria) • Sickle-Cell Anemia • Tay-Sachs disease • Cystic Fibrosis

23. Genetic Abnormalities • Dominant gene abnormalities • Huntington’s disease • Sex-linked abnormalities • Hemophilia • Duchenne muscular dystrophy

24. Genetic Counseling and Prenatal Testing • Genetic Counseling • Addresses probability of genetic abnormalities

25. Genetic Counseling and Prenatal Testing • Amniocentesis • Routine among American women over age 35 • Used to detect over 100 chromosomal and genetic abnormalities • Indicates the sex of the baby • Some risk of miscarriage

26. Figure 2.6 Amniocentesis

27. Genetic Counseling and Prenatal Testing • Chorionic Villus Sampling (CVS) • Can diagnosis abnormalities earlier than amniocentesis • Slightly greater risk of spontaneous abortion • Ultrasound • Sonogram “picture” of fetus • Beneficial in determining position of fetus • Blood Tests • Alpha-Fetoprotein (AFP) assay

28. Lessons in Observation: Prenatal Assessment

29. Lessons in Observation: Prenatal Assessment • What is the most common chromosomal abnormality seen in live-born babies? • Is an amniocentesis recommended for Eleanor? Why or why not?

30. Lessons in Observation: Prenatal Assessment • According to the ultrasound results, what is the position of the baby? • Describe the two structural abnormalities and/or marker of chromosomal abnormalities discussed as the ultrasound is performed.

31. Lessons in Observation: Prenatal Assessment • What risks are associated with various prenatal assessment measures? • How prevalent are birth defects resulting from genetic factors?

32. Lessons in Observation: Prenatal Assessment • What are some other, non-genetic factors that can affect prenatal development? • Eleanor took some careful planned actions (taking vitamins and eliminating alcohol consumption). What problems will this likely rule out?

33. Heredity and the Environment Nature versus Nurture

34. What Is the Difference Between Our Genotypes and Our Phenotypes? • Genotypes • Set of traits inherited from parents • Phenotypes • Actual sets of traits – product of genetics and environment

35. Using Research to Sort Out the Effects of Genetics and Environmental Influences on Development • Kinship studies • Genetic closeness of relatives • Twin Studies • Monozygotic twins share 100% of genes • Dizygotic twins share 50% of genes (same as other siblings) • Reared together versus reared apart • Adoption studies

36. Conception Against All Odds

37. Conception: Against All Odds • Ova • Begin to mature at puberty • Monthly release of mature egg into Fallopian tube • Egg is propelled by cilia • If not fertilized, egg is discharged in the menstrual flow

38. Conception: Against All Odds • Sperm • Self propelled, and smaller than ova • Sperm with Y chromosome swim faster than sperm with X chromosome • From 200 to 400 million in ejaculate; only 1 in 1,000 arrive in vicinity of ovum • Sperm are attracted by chemical odor secreted by ova

39. Figure 2.9 Female Reproductive Organs

40. What Process Brings Together the Genes From Each Parent? • Only one sperm enters the zona pellucida • Sperm secrete enzyme hyaluronidase to allow penetration of the zona pellucida • When one sperm enters, the zona pellucida thickens, locking out other sperm • Chromosomes from sperm and egg combine to form 23 new pairs

41. Infertility and Other Ways of Becoming Parents: What Are the Causes of Infertility? • Major fertility problems among men • Low sperm count • Deformed sperm • Low sperm motility • Infections diseases • Direct trauma to testes • Causes • Genetic factors, environmental poisons, diabetes, STI’s, overheating testes, pressure to testes, aging and effects of drugs

42. Infertility and Other Ways of Becoming Parents: What Are the Causes of Infertility? • Major fertility problems among women • Failure to ovulate • Fertility drugs are used to cause women to ovulate • Infections • Pelvic inflammatory disease (PID) • Endometriosis • Obstruct Fallopian tubes • Barriers of disorders in passageways (i.e., Fallopian tubes)

43. Infertility and Other Ways of Becoming Parents: How Are Couples Helped to Have Children? • Artificial insemination • Sperm injected into mother’s uterus • In Vitro Fertilization • Ova and sperm are fertilized, then implanted in mother’s uterus • Donor IVF • Ovum harvested from donor woman; fertilized in vitro and implanted in recipient’s uterus

44. Infertility and Other Ways of Becoming Parents • Surrogate Mothers • Surrogate “substitutes” bring babies to term for another woman • Adoption • Option chosen by singles and infertile couples

45. Selecting the Sex of Your Child • Cultural Folklore • Sperm-Separation Procedures • Preimplantation Genetic Diagnosis (PGD) • Moral and Ethical Questions