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Chapter 7 Human Heredity by Michael Cummings ©2006 Brooks/Cole-Thomson Learning Chapter 7 Development and Sex Determination.

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Presentation on theme: "Chapter 7 Human Heredity by Michael Cummings ©2006 Brooks/Cole-Thomson Learning Chapter 7 Development and Sex Determination."— Presentation transcript:

1 Chapter 7 Human Heredity by Michael Cummings ©2006 Brooks/Cole-Thomson Learning Chapter 7 Development and Sex Determination

2 Chapter 7 Human Heredity by Michael Cummings ©2006 Brooks/Cole-Thomson Learning Sexual Differentiation in Humans Begins in the 7 th week of development Is influenced by genetic and environmental factors

3 Chapter 7 Human Heredity by Michael Cummings ©2006 Brooks/Cole-Thomson Learning Human Reproductive System –Zygote fertilized egg (diploid) –Gametesunfertilized germ cells –Spermmale gamete (haploid) –Oocytefemale gamete (haploid) –Gonadsorgans where gametes and sex hormones are produced (testes and ovaries)

4 Chapter 7 Human Heredity by Michael Cummings ©2006 Brooks/Cole-Thomson Learning Male Reproductive System Fig. 7.1

5 Chapter 7 Human Heredity by Michael Cummings ©2006 Brooks/Cole-Thomson Learning Spermatogenesis Fig. 7.2

6 Chapter 7 Human Heredity by Michael Cummings ©2006 Brooks/Cole-Thomson Learning Spermatogenesis

7 Chapter 7 Human Heredity by Michael Cummings ©2006 Brooks/Cole-Thomson Learning Spermatogenesis

8 Chapter 7 Human Heredity by Michael Cummings ©2006 Brooks/Cole-Thomson Learning Seminiferous tubule filled with sperm. SEM X335. Credit: © Dr. Richard Kessel & Dr. Gene Shih/Visuals Unlimited 99917

9 Chapter 7 Human Heredity by Michael Cummings ©2006 Brooks/Cole-Thomson Learning Human sperm. TEM. Credit: © Dr. David Phillips/Visuals Unlimited 99895

10 Chapter 7 Human Heredity by Michael Cummings ©2006 Brooks/Cole-Thomson Learning Human sperm. TEM. Credit: © Dr. David Phillips/Visuals Unlimited

11 Chapter 7 Human Heredity by Michael Cummings ©2006 Brooks/Cole-Thomson Learning Female Reproductive System Fig. 7.3

12 Chapter 7 Human Heredity by Michael Cummings ©2006 Brooks/Cole-Thomson Learning Fig. 7-4, p.155 Ovary Stepped Art

13 Chapter 7 Human Heredity by Michael Cummings ©2006 Brooks/Cole-Thomson Learning Fig. 7-4, p.155 Primary oocyte, not yet released from meiosis I. A cell layer is forming around it. A follicle consists of the cell layer and the oocyte. Ovary Primordial follicle Stepped Art

14 Chapter 7 Human Heredity by Michael Cummings ©2006 Brooks/Cole-Thomson Learning Fig. 7-4, p.155 Primary oocyte, not yet released from meiosis I. A cell layer is forming around it. A follicle consists of the cell layer and the oocyte. A transparent and somewhat elastic layer, the zona pellucida, starts forming around the primary oocyte. Ovary Primordial follicle Stepped Art

15 Chapter 7 Human Heredity by Michael Cummings ©2006 Brooks/Cole-Thomson Learning Fig. 7-4, p.155 Primary oocyte, not yet released from meiosis I. A cell layer is forming around it. A follicle consists of the cell layer and the oocyte. A transparent and somewhat elastic layer, the zona pellucida, starts forming around the primary oocyte. Ovary Primordial follicle A fluid-filled cavity (antrum) starts forming in the follicle’s cell layer. Stepped Art

16 Chapter 7 Human Heredity by Michael Cummings ©2006 Brooks/Cole-Thomson Learning Fig. 7-4, p.155 Primary oocyte, not yet released from meiosis I. A cell layer is forming around it. A follicle consists of the cell layer and the oocyte. A transparent and somewhat elastic layer, the zona pellucida, starts forming around the primary oocyte. Mature follicle. Meiosis I is over. The secondary oocyte and first polar body are now formed. Secondary oocyte First polar body Ovary Primordial follicle A fluid-filled cavity (antrum) starts forming in the follicle’s cell layer. Stepped Art

17 Chapter 7 Human Heredity by Michael Cummings ©2006 Brooks/Cole-Thomson Learning Fig. 7-4, p.155 Primary oocyte, not yet released from meiosis I. A cell layer is forming around it. A follicle consists of the cell layer and the oocyte. A transparent and somewhat elastic layer, the zona pellucida, starts forming around the primary oocyte. Mature follicle. Meiosis I is over. The secondary oocyte and first polar body are now formed. Secondary oocyte First polar body Ovulation. The mature follicle ruptures, releasing the secondary oocyte and first polar body. Ovary Primordial follicle A fluid-filled cavity (antrum) starts forming in the follicle’s cell layer. Stepped Art

18 Chapter 7 Human Heredity by Michael Cummings ©2006 Brooks/Cole-Thomson Learning Fig. 7-4, p.155 Primary oocyte, not yet released from meiosis I. A cell layer is forming around it. A follicle consists of the cell layer and the oocyte. A transparent and somewhat elastic layer, the zona pellucida, starts forming around the primary oocyte. Mature follicle. Meiosis I is over. The secondary oocyte and first polar body are now formed. Secondary oocyte First polar body Ovulation. The mature follicle ruptures, releasing the secondary oocyte and first polar body. A corpus luteum forms from remnants of the ruptured follicle. Ovary Primordial follicle A fluid-filled cavity (antrum) starts forming in the follicle’s cell layer. Stepped Art

19 Chapter 7 Human Heredity by Michael Cummings ©2006 Brooks/Cole-Thomson Learning Fig. 7-4, p.155 Primary oocyte, not yet released from meiosis I. A cell layer is forming around it. A follicle consists of the cell layer and the oocyte. A transparent and somewhat elastic layer, the zona pellucida, starts forming around the primary oocyte. Mature follicle. Meiosis I is over. The secondary oocyte and first polar body are now formed. The corpus luteum breaks down when the woman doesn’t get pregnant. Secondary oocyte First polar body Ovulation. The mature follicle ruptures, releasing the secondary oocyte and first polar body. A corpus luteum forms from remnants of the ruptured follicle. Ovary Primordial follicle A fluid-filled cavity (antrum) starts forming in the follicle’s cell layer. Stepped Art

20 Chapter 7 Human Heredity by Michael Cummings ©2006 Brooks/Cole-Thomson Learning Credit: © Gary Martin/Visuals Unlimited Ovulation

21 Chapter 7 Human Heredity by Michael Cummings ©2006 Brooks/Cole-Thomson Learning Timing of Meiosis and Spermatogenesis Large numbers of sperm are in constant production Four functional, equally-sized gametes per primary spermatocyte Over a lifetime a male produces billions of sperm Spermatogenesis takes approximately 48 days Each ejaculation can contain 200-400m sperm

22 Chapter 7 Human Heredity by Michael Cummings ©2006 Brooks/Cole-Thomson Learning Timing of Meiosis and Oogenesis Unequal cytoplasmic division and produces 1 large functional gamete and 3 nonfunctional polar bodies Primary oocytes are produced prior to birth and are held in meiosis I After puberty, one oocyte completes meiosis I each monthly cycle, starts meiosis II and arrests at metaphase of meiosis II If fertilization occurs, it completes meiosis II Time for complete cycle is 12–50 years Release about 450 oocytes in a lifetime

23 Chapter 7 Human Heredity by Michael Cummings ©2006 Brooks/Cole-Thomson Learning

24 1 spermatogonium  4 mature sperm 1 oogonium  1 oocyte + 3 polar bodies

25 Chapter 7 Human Heredity by Michael Cummings ©2006 Brooks/Cole-Thomson Learning Fertilization to Implantation Fertilization is the fusion of two gametes to produce a zygote Zygote is moved by cilia in the lining of the oviduct to the uterus The zygote divides by mitosis Forms a early embryonic stage, the blastocyst

26 Chapter 7 Human Heredity by Michael Cummings ©2006 Brooks/Cole-Thomson Learning Sperm enter vagina Ovulation Vagina Opening of cervix Uterus Ovary Oviduct Fertilization Stepped Art Fig. 7-5b, p.157

27 Chapter 7 Human Heredity by Michael Cummings ©2006 Brooks/Cole-Thomson Learning Sperm enter vagina Zona pellucida Follicle cell Ovulation Vagina Opening of cervix Uterus Ovary Oviduct Fertilization Egg nucleus Stepped Art Fig. 7-5b, p.157

28 Chapter 7 Human Heredity by Michael Cummings ©2006 Brooks/Cole-Thomson Learning Sperm enter vagina Zona pellucida Follicle cell Ovulation Vagina Opening of cervix Uterus Ovary Oviduct Fertilization Egg nucleus Stepped Art Fig. 7-5b, p.157

29 Chapter 7 Human Heredity by Michael Cummings ©2006 Brooks/Cole-Thomson Learning Sperm enter vagina Nuclei fuse Fusion of sperm nucleus with egg nucleus Zona pellucida Follicle cell Ovulation Vagina Opening of cervix Uterus Ovary Oviduct Fertilization Egg nucleus Stepped Art Fig. 7-5b, p.157

30 Chapter 7 Human Heredity by Michael Cummings ©2006 Brooks/Cole-Thomson Learning Sperm enter vagina Nuclei fuse Fusion of sperm nucleus with egg nucleus Zona pellucida Follicle cell Ovulation Vagina Opening of cervix Uterus Ovary Oviduct Fertilization Egg nucleus Stepped Art Fig. 7-5b, p.157

31 Chapter 7 Human Heredity by Michael Cummings ©2006 Brooks/Cole-Thomson Learning Sperm entering the oviduct. SEM X500. Credit: © Dr. David Phillips/Visuals Unlimited 350626

32 Chapter 7 Human Heredity by Michael Cummings ©2006 Brooks/Cole-Thomson Learning Fertilization. SEM X4700. Credit: © Dr. David Phillips/Visuals Unlimited 167105

33 Chapter 7 Human Heredity by Michael Cummings ©2006 Brooks/Cole-Thomson Learning Cleavage and gastrulation (Xenopus embryo)

34 Chapter 7 Human Heredity by Michael Cummings ©2006 Brooks/Cole-Thomson Learning Blastocyst Mass of approximately 100 cells It has two parts –Inner cell mass gives rise to the embryo –Trophoblast gives rise to surrounding membranes

35 Chapter 7 Human Heredity by Michael Cummings ©2006 Brooks/Cole-Thomson Learning Implantation The trophoblast attaches to the endometrium of the uterus Villi (finger like projections) grow into the endometrium and anchor the embryo After approximately 12 days, the trophoblast has formed the chorion Chorion secretes human chorionic gonadotropin (hCG) which maintains the uterine lining (pregnancy test)

36 Chapter 7 Human Heredity by Michael Cummings ©2006 Brooks/Cole-Thomson Learning Placenta Highly vascular Formed from the chorionic villi Allows oxygen, wastes, nutrients, and other molecules to be exchanged between the mother and child Membranes that connect the embryo to the placenta form the umbilical cord Source of stem cells

37 Chapter 7 Human Heredity by Michael Cummings ©2006 Brooks/Cole-Thomson Learning Fig. 7-6a-e, p.159 Stepped Art Endometrium Fertilization Implantation

38 Chapter 7 Human Heredity by Michael Cummings ©2006 Brooks/Cole-Thomson Learning Fig. 7-6a-e, p.159 Stepped Art Endometrium Fertilization Implantation DAYS 1-2

39 Chapter 7 Human Heredity by Michael Cummings ©2006 Brooks/Cole-Thomson Learning Fig. 7-6a-e, p.159 Stepped Art Endometrium Fertilization Implantation DAYS 1-2DAY 3

40 Chapter 7 Human Heredity by Michael Cummings ©2006 Brooks/Cole-Thomson Learning Fig. 7-6a-e, p.159 Stepped Art Endometrium Fertilization Implantation DAYS 1-2DAY 3DAY 4

41 Chapter 7 Human Heredity by Michael Cummings ©2006 Brooks/Cole-Thomson Learning Fig. 7-6a-e, p.159 Stepped Art Endometrium Fertilization Implantation DAYS 1-2DAY 3DAY 4DAY 5

42 Chapter 7 Human Heredity by Michael Cummings ©2006 Brooks/Cole-Thomson Learning Fig. 7-6a-e, p.159 Stepped Art Endometrium Fertilization Implantation Inner cell mass DAYS 1-2DAY 3DAY 4DAY 5

43 Chapter 7 Human Heredity by Michael Cummings ©2006 Brooks/Cole-Thomson Learning Fig. 7-6a-e, p.159 Stepped Art Trophoblast (surface layer of cells of the blastocyst) Uterine cavity Endometrium Inner cell mass Fertilization Implantation Inner cell mass Endometrium blastocoel DAYS 1-2DAY 3DAY 4DAY 5 DAYS 6-7

44 Chapter 7 Human Heredity by Michael Cummings ©2006 Brooks/Cole-Thomson Learning Fig. 7-6f-h, p.159

45 Chapter 7 Human Heredity by Michael Cummings ©2006 Brooks/Cole-Thomson Learning Fig. 7-6f-h, p.159 DAYS 10–11 Start of yolk sac Start of embryonic disk Start of amniotic cavity Stepped Art

46 Chapter 7 Human Heredity by Michael Cummings ©2006 Brooks/Cole-Thomson Learning Fig. 7-6f-h, p.159 DAYS 10–11 DAY 12 Start of chorionic cavity Start of yolk sac Start of embryonic disk Start of amniotic cavity Blood-filled spaces Stepped Art

47 Chapter 7 Human Heredity by Michael Cummings ©2006 Brooks/Cole-Thomson Learning Fig. 7-6f-h, p.159 DAYS 10–11 DAY 12DAY 14 Connective tissue Amniotic cavity Chorion Chorionic villi Chorionic cavity Start of chorionic cavity Start of yolk sac Start of embryonic disk Start of amniotic cavity Yolk sac Blood-filled spaces Stepped Art

48 Chapter 7 Human Heredity by Michael Cummings ©2006 Brooks/Cole-Thomson Learning Fig. 7-7a1, p.160 Connecting stalk WEEKS 5–6WEEK 4 Yolk sac Embryo

49 Chapter 7 Human Heredity by Michael Cummings ©2006 Brooks/Cole-Thomson Learning Fig. 7-7a2, p.160 Forebrain Future lens Pharyngeal arches Developing heart Upper limb bud Somites Neural tube forming Lower limb bud Tail

50 Chapter 7 Human Heredity by Michael Cummings ©2006 Brooks/Cole-Thomson Learning Fig. 7-7b, p.160 Umbilical cord formation between weeks 4 and 8 (amnion expands, forms tube that encloses the connecting stalk and a duct for blood vessels) Head growth exceeds growth of other regions Retinal pigment Future external ear Foot plate Upper limb differentiation (hand plates develop, then digital rays of future fingers; wrist, elbow start forming)

51 Chapter 7 Human Heredity by Michael Cummings ©2006 Brooks/Cole-Thomson Learning Fig. 7-7c1, p.161 WEEK 8 Placenta WEEK 16

52 Chapter 7 Human Heredity by Michael Cummings ©2006 Brooks/Cole-Thomson Learning Fig. 7-7c2, p.161 Upper and lower limbs well formed; fingers and then toes have separated Final week of embryonic period; embryo looks distinctly human compared to other vertebrate embryos Tail has become stubby Primordial tissues of all internal, external structures now developed

53 Chapter 7 Human Heredity by Michael Cummings ©2006 Brooks/Cole-Thomson Learning Fig. 7-7d, p.161 During fetal period, length measurement extends from crown to heel (for embryos, it is the longest measurable dimension, as from crown to rump). WEEK 16 Length: 16 centimeters (6.4 inches) Weight: 200 grams (7 ounces) WEEK 38 (full term) Length: 50 centimeters (20 inches) Weight: 3,400 grams (7.5 pounds) WEEK 29 Length: 27.5 centimeters (11 inches) Weight: 1,300 grams (46 ounces)

54 Chapter 7 Human Heredity by Michael Cummings ©2006 Brooks/Cole-Thomson Learning Congenital Malformations 97% of babies are normal at birth Birth defects can be produced by genetic disorders or exposure to environmental agents Most are caused by disruptions in embryonic development Brain and nervous system may be damaged throughout development

55 Chapter 7 Human Heredity by Michael Cummings ©2006 Brooks/Cole-Thomson Learning -Teratogens are environmental agents that cause developmental disruptions Sources of teratogens Natural in environment -skunk cabbage contains cyclopamine, which inhibits cholesterol biosynthesis, preventing a key developmental pathway from working; Toxoplasma gondii - cat-borne - leads to stillbirths Infectious agents -Rubella (German measles), blindness, hearing loss, heart defects, mental retardation Human introduced in the environment -methylmercury, fungicide, central nervous system disorders, cerebral palsy, mental retardation Drugs -Diethylstilbesterol (DES), synthetic estrogen, used to prevent miscarriage until 1971 (it didn’t work), structural damage to reproductive organs, increased cancer risk

56 Chapter 7 Human Heredity by Michael Cummings ©2006 Brooks/Cole-Thomson Learning Diethylstilbestrol (DES) -prescribed to ~5 million women 1938-1971 -used to prevent miscarriage and preterm labor -shown not to be effective in the 1950s, continued to be prescribed -1970s, women exposed to DES in utero had increased cervical cancer risk, morphological abnormalities of reproductive tract -men exposed in utero often had abnormal genitalia

57 Chapter 7 Human Heredity by Michael Cummings ©2006 Brooks/Cole-Thomson Learning The Effects of Teratogens Fig. 7.8

58 Chapter 7 Human Heredity by Michael Cummings ©2006 Brooks/Cole-Thomson Learning Fetal Alcohol Syndrome (FAS) A serious and widespread teratogenic problem Fetal Alcohol Syndrome – 1.9/1,000 births Fetal alcohol effect 3.5/1,000 births Preventable

59 Chapter 7 Human Heredity by Michael Cummings ©2006 Brooks/Cole-Thomson Learning Fetal alcohol syndrome -characterized by small heads, low nose bridge, small brain size, mental retardation -third most common cause of mental retardation (after Fragile X and Down’s) -FAS affects 1 out of 500-750 newborns in the US FASnormal -intellectual and behavioral problems seen even in the absence of morphological defects

60 Chapter 7 Human Heredity by Michael Cummings ©2006 Brooks/Cole-Thomson Learning Alcohol Consumption During Pregnancy Can Result in: Spontaneous abortion Growth retardation Facial abnormalities Mental retardation Learning disabilities


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