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Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Powerpoint Lecture Outline Human Genetics Concepts and Applications Eighth Edition Ricki Lewis Prepared by Dubear Kroening University of Wisconsin-Fox Valley 3-1 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Chapter 3 Development 3-2 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Stages of the Human Life Cycle • Genes orchestrate our physiology after conception through adulthood • Development is the process of forming an adult from a single-celled embryo • In humans, new individuals form from the union of sex cells or gametes – Sperm from the male and oocyte from the female form a zygote 3-3 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Gametes • Form from cell division of germline cells • Meiosis is cell division to produce gametes • Meiosis has two divisions of the nucleus (Meiosis I and Meiosis II) and produces cells with half the number of chromosomes (haploid) 3-4 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Meiosis • Reduces the genetic material by half • Why is this necessary? from mother from father child too much! meiosis reduces genetic content 3-5 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Homologous Chromosomes • Carry the same genes • Pair during Meiosis I • Separate in the formation of gametes • One copy of each pair is from the mother and one is from the father. Figure 1.2 3-6 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Sexual Reproduction • Meiosis and sexual reproduction increases genetic diversity in a population • Variation is important in a changing environment • Evolution is the genetic change in a population over time 3-7 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Comparison of Mitosis and Meiosis Table 3.1 3-8 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Meiosis: Cell Division in Two Parts Meiosis I (reduction division) Meiosis II (equational division) Diploid Haploid Haploid Figure 3.3 Result: one copy of each chromosome in a gamete. 3-9 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Meiosis Interphase precedes meiosis I Meiosis I Meiosis II Prophase I Prophase II Metaphase I Metaphase II Anaphase I Anaphase II Telophase I Telophase II Figure 2.13 3-10 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Meiosis I : the reduction division Spindle fibers Nucleus Nuclear envelope Prophase I (early) (diploid) Prophase I (late) (diploid) Metaphase I (diploid) Anaphase I (diploid) Telophase I (diploid) Figure 3.4 3-11 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Prophase I Late prophase Early prophase • Chromosomes condense • Homologs pair • Spindle forms • Crossing over occurs • Nuclear envelope fragments Figure 3.4 3-12 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Metaphase I • Homolog pairs align along the equator of the cell Figure 3.4 3-13 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Anaphase I • Homologs separate and move to opposite poles • Sister chromatids remain attached at their centromeres Figure 3.4 3-14 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Telophase I • Nuclear membrane reforms • Spindle disappears • Cytokinesis divides cell Figure 3.4 3-15 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Meiosis II : the equational division Prophase II (haploid) Figure 3.4 Metaphase II (haploid) Anaphase II (haploid) Telophase II (haploid) Four nonidentical haploid daughter cells 3-16 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Prophase II • Nuclear envelope fragments • Spindle forms Figure 3.4 3-17 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Metaphase II • Chromosomes align along equator of cell Figure 3.4 3-18 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Anaphase II • Centromeres divide • Sister chromatids separate Figure 3.4 3-19 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Telophase II • Nuclear envelopes reform • Chromosomes decondense • Spindle disappears • Cytokinesis divides cells Figure 3.4 3-20 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Results of Meiosis Gametes • Four haploid cells • Contain one copy of each chromosome and one allele of each gene • Each cell is unique Figure 3.4 3-21 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Table 3.1 3-22 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Recombination (crossing over) • Occurs in prophase of meiosis I A A B B C • Homologous chromosomes exchange genes • Generates diversity b C D D E F E F a a e f c b c d d e f Figure 3.5 3-23 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Recombination (crossing over) A a B • Exchange between homologs • Occurs in prophase I C C c D D E F d E F e f b c d e f Figure 3.5 Letters denote genes and case denotes alleles 3-24 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Recombination (crossing over) a A B b C •Creates chromosomes with new combinations of alleles for genes A to F D E F A a B c b c d d C D E F e f e f Figure 3.5 3-25 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Chiasmata In prophase I, crossing over or recombination events create chiasmata. Figure 3.5 3-26 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Independent Assortment The homolog of one chromosome can be inherited with either homolog of a second chromosome. Figure 3.6 3-27 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Spermatogenesis: sperm formation Figure 3.7 3-28 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Spermatogenesis • Stem cells in testes divide mitotically to produce spermatocytes •. Spermatocytes divide by meiosis to produce four equal sized haploid spermatids that mature into four sperm Figure 3.9 3-29 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Oogenesis Figure 3.11 3-30 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Oogenesis: Ovum Formation • • • • Cells of the ovary divide to form oocytes Oocytes divide by meiosis Unequal cytoplasmic division A discontinuous process – At birth, oocytes are arrested in prophase I – At ovulation, an oocyte continues to metaphase II • The four meiotic products produce a functional ovum and three polar bodies. 3-31 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Fertilization The ovum completes meiosis II after fertilization Figure 3.13 • Fertilization is the union of sperm and ovum • After fertilization, chemical reactions occur preventing additional sperm from entering the ovum 3-32 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Stages of Development Table 3.2 3-33 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Early Development: Ovulation to Implantation Figure 3.14 3-34 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Cleavage • Mitotic cell division; a morula • Cells are called blastomeres • The developing embryo becomes a blastocyst, a hollow ball of cells 3-35 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Blastocyst • The inner cell mass (ICM) develops into the embryo • Other cells become the extraembryonic membranes important for implantation and support of embryonic growth 3-36 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Gastrulation • Primary germ layers form • Cells differentiate • Supporting structures form – Chorionic villi – Yolk sac – Allantois – By 10 weeks the placenta is fully formed 3-37 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Germ Layers: Endoderm, Mesoderm, and Ectoderm Figure 3.15 3-38 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Germ Layers Ectoderm: the outermost germ layer develops skin nervous system eye lens Mesoderm: the middle germ layer develops muscle connective tissue blood vessels kidneys Endoderm: the innermost germ layer develops lining of GI tract liver pancreas thymus 3-39 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Multiple Births Dizygotic twins • Form from two differ zygotes • Two ova are fertilized • Same genetic relationship as any siblings Monozygotic twins • One ova is fertilized • Developing embryo splits during early development • Genetically identical 3-40 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Figure 3.16 3-41 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Embryo Develops Figure 3.18 3-42 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Critical Periods of Development • Organs develop at different times: a critical period • During its critical period, an organ is vulnerable to toxins, viruses, and genetic abnormalities • Altering the normal development may cause birth defects 3-43 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Critical Periods of Development Figure 3.20 3-44 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Teratogens • Cause birth defects during development • Examples – Thalidomide – Cocaine – Cigarettes – Alcohol – Some nutrients – Some viruses 3-45 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. • Fetal • Alcohol Syndrome Figure 3.21 • Fetal Alcohol Syndrome 3-46 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Maturation and Aging • Genes may impact health throughout life • Single gene disorders are expressed early in life and tend to be recessive • Adult onset single gene traits are often dominant • Interaction between genes and environmental factors Example: malnutrition before birth coronary artery disease , stroke, hypertension , type 2 diabetes 3-47 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Table 3.3 3-48 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Aging • Segmental progeroid syndromesaccelerated aging • Increases the rate of aging associated changes • Inheritance of longevity –chromosome 4 3-49 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Table 3.4 3-50