Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 3-1 Human Genetics Concepts and Applications Eighth Edition Powerpoint Lecture Outline Ricki Lewis Prepared by Dubear Kroening University of Wisconsin-Fox Valley

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 3-2 Chapter 3 Development

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 3-3 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

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 3-4 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)

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 3-5 Meiosis Reduces the genetic material by half Why is this necessary? from motherfrom fatherchild meiosis reduces genetic content too much!

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 3-6 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

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 3-7 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

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 3-8 Comparison of Mitosis and Meiosis Table 3.1

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 3-9 Meiosis: Cell Division in Two Parts Result: one copy of each chromosome in a gamete. Haploid Diploid Meiosis I (reduction division) Meiosis II (equational division) Haploid Figure 3.3

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Meiosis Interphase precedes meiosis I Meiosis I Prophase I Metaphase I Anaphase I Telophase I Meiosis II Prophase II Metaphase II Anaphase II Telophase II Figure 2.13

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Meiosis I : the reduction division Prophase I (early) (diploid) Prophase I (late) (diploid) Metaphase I (diploid) Anaphase I (diploid) Telophase I (diploid) Nucleus Spindle fibers Nuclear envelope Figure 3.4

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Early prophase Homologs pair Crossing over occurs Prophase I Late prophase Chromosomes condense Spindle forms Nuclear envelope fragments Figure 3.4

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

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

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

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Meiosis II : the equational division Prophase II (haploid) Metaphase II (haploid) Anaphase II (haploid) Telophase II (haploid) Four nonidentical haploid daughter cells Figure 3.4

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Prophase II Nuclear envelope fragments Spindle forms Figure 3.4

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Metaphase II Chromosomes align along equator of cell Figure 3.4

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Anaphase II Centromeres divide Sister chromatids separate Figure 3.4

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

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

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Table 3.1

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Recombination (crossing over) Occurs in prophase of meiosis I Homologous chromosomes exchange genes Generates diversity a b c d e f A B C D E F A B C D E F a b c d e f Figure 3.5

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Recombination (crossing over) Exchange between homologs Occurs in prophase I A B C D E F a b c d e f c d e f A B a b C D E F Letters denote genes and case denotes alleles Figure 3.5

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Recombination (crossing over) Creates chromosomes with new combinations of alleles for genes A to F A B C D E F a b c d e f c d e f A B a b C D E F Figure 3.5

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

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

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Spermatogenesis: sperm formation Figure 3.7

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

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Oogenesis Figure 3.11

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.

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Fertilization Fertilization is the union of sperm and ovum After fertilization, chemical reactions occur preventing additional sperm from entering the ovum The ovum completes meiosis II after fertilization Figure 3.13

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Stages of Development Table 3.2

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Early Development: Ovulation to Implantation Figure 3.14

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

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

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

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Germ Layers: Endoderm, Mesoderm, and Ectoderm Figure 3.15

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Germ Layers Endoderm: the innermost germ layer develops lining of GI tract liver pancreas thymus Ectoderm: the outermost germ layer develops skin nervous system eye lens Mesoderm: the middle germ layer develops muscle connective tissue blood vessels kidneys

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

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Figure 3.16

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Embryo Develops Figure 3.18

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

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Critical Periods of Development Figure 3.20

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

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Figure 3.21 Fetal Alcohol Syndrome Fetal Alcohol Syndrome

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

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Table 3.3

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Aging Segmental progeroid syndromes- accelerated aging Increases the rate of aging associated changes Inheritance of longevity –chromosome 4

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Table 3.4