Chapter 9: Reproduction Lecture Presentation PDF

 Key Questions What is asexual reproduction and how does it differ from sexual reproduction. Provide examples of asexual reproduction. What are homologous chromosomes? How many homologous chromosomes do humans have? What is a karyotype? What can we learn by...

 Key Questions What is asexual reproduction and how does it differ from sexual reproduction. Provide examples of asexual reproduction. What are homologous chromosomes? How many homologous chromosomes do humans have? What is a karyotype? What can we learn by looking at a karyotype? Differentiate between haploid and diploid numbers. Define meiosis and explain its importance. List and describe the events of meiosis I. List and describe the events of meiosis II. How does nondisjunction happen during meiosis? What does it result in? How do mutations, crossing over, segregation of chromosomes, independent assortment of chromosomes, and random fertilization all contribute to genetic variation? Compare and contrast mitosis and meiosis. List and describe the functions of primary and accessory reproductive organs in males and females. List and describe the functions of hormones that control reproduction in males and females. List and describe the events of the ovarian and uterine cycle of a female. Explain the importance of their overlapping. Explain how spermatogenesis and oogenesis differ as well as the factors that control these factors. Describe the process of fertilization. Describe the major events of human embryonic fertilization. What are some hormones and physiological changes that occur during pregnancy? 9.1 Asexual vs. Sexual Reproduction Asexual: organisms form clones Sexual: occurs via gametes Homologous Chromosomes A complete set of identical chromosomes inherited by each parent Mitosis vs Meiosis Mitosis (asexual): Occurs in body cells Cell replication that forms new body cells to replace old/injured cells Forms 2 identical daughter cells each Mitosis vs Meiosis Meiosis (sexual): Occurs in the testes & ovaries Cell replication that forms gametes (sex cells) Forms 4 daughter cells each with the haploid chromosomes (23 Karyotype Polyploidy Having extra sets of chromosomes (3n, 4n, 8n, etc.) Caused by nondisjunction of all chromosomes Rare, usually fatal in animals Common in plants (30-80%) polyploids often thrive better and grow taller some are sterile (seedless)  Interphase: MeiosisG1 S  G2 Meiosis I: 1. Prophase I 2. Metaphase I 3. Anaphase I 4. Telophase I Cytokinesis I Meiosis II: 5. Prophase II 6. Metaphase II 7. Anaphase II 8. Telophase II Cytokinesis  9.2 The Process of Meiosis I 2 pairs of homologous chromosomes 1 pair long to represent one set and the other pair short Pink came from the mother Blue came from the father 1 pink long, 1 blue long 1 pink short, 1 blue short 9.2 Cell Cycle of Sex Cells Begins with Interphase  Meiosis I: Prophase I animation Meiosis I Prophase I Crossing over Meiosis I: Metaphase I Tetrads (homologous chromosome pairs) randomly line up in the middle of the cell Centromere attaches to a spindle fiber  Meiosis I: Anaphase I Homologous chromosome pairs separate Centromeres to not break Segregation & Independent Assortment animation  Meiosis I: Telophase I Cytokinesis: cell separates into 2 daughter cells Each chromosome contains 2 identical chromatids (1 chromosome) – cells are haploid Meiosis I  No Interphase II Cells do briefly rest between Meiosis I & II No replication of DNA  9.3 Meiosis II – Prophase II very similar to prophase in mitosis  Meiosis II – Metaphase II very similar to metaphase in mitosis  Meiosis II – Anaphase II very similar to anaphase in mitosis  Meiosis II – Telophase II very similar to telophase in mitosis Meiosis I and II Differences between male and female meiosis BioFlix: Meiosis  Meiosis Video https://www.youtube.com/watch?v=k Qu6Yfrr6j0  9.4 Sources of Variation 1.) Mutations (change in DNA sequence) 2.) Crossing Over of Genes 3.) Independent Assortment & Segregation 4.) Random Fertilization  Sources of Variation - Mutations Alterations in DNA (genes) Base changes  Sources of Variation – Cross- Overs Exchange of genes between chromatids Recombinant chromosomes (DNA) Genes occupy a locus – genes close together move together: Linked Genes Sources of Variation – Cross- Overs  Sources of Variation – Independent Assortment & Segregation Homologous chromosomes separate based on how they line up. Chromosomes are “sorted” into daughter cells based on how they line up in metaphase. Different sequences results in different combinations  Independent Assortment 2n where n= #pairs of chromosomes Cell with 3 pairs can have 8 different daughter cell combinations. 23 = 2 X 2 X 2 = 8 Humans 23 pairs: 8,388,608  Sources of Variation – Random Fertilization Random sperm/egg 1 in 72,000,000,000,000 Chromosome Abnormalities Non-disjunction: – When chromosomes fail to separate correctly during meiosis I or meiosis II – Results in loss or gain of chromosomes in egg or sperm cells – Examples: Trisomy Monosomic 9.5 Chromosome Abnormalities  Nondisjunction of Sex Chromosomes Klinefelter Syndrome: XXY; male Turner Syndrome: XO; female Down Syndrome  Down Syndrome Amniocentesis Procedure to extract fetal cells and examine chromosomes Sex Chromosomes Chromosome Mutations  Chromosome Mutations Translocation Chromosome Chronic duplication myelogenous Fragile X leukemia Fragile X Syndrome  9.6 Sex Chromosomes & Biological Sex Determination XX or XY Y chromosome triggers release of testosterone for the development of a male. Females: oogenesis begins and stops in meiosis I Karyotype 9.7 Sexual Development  Male Reproductive Anatomy Primary Organs Accessory Organs Testes  Epididymis Seminiferous Tubules  Vas Deferens make sperm  Seminal Vesicle Interstitial Cells  Prostate Gland make testosterone  Bulbourethral Penis Gland Spermatogenesis All 4 cells made during meiosis will become sperm cells  Hormone Regulation Gonadotropin-releasing hormone (GnRH): from hypothalamus controls hormone release from anterior pituitary: FSH and LH Follicle-stimulating hormone FSH: triggers spermatogenesis & production of semen Luteinizing Hormone (LH): triggers production of testosterone  Hormone Regulation Testosterone Secondary sex characteristics  Female Reproductive Anatomy Primary Organs Accessory Organs Ovaries  Fallopian (uterine) Follicles contain tubes oocytes & make  Uterus estrogen  Vagina Oogenesis egg supply determined by birth puberty --> menopause releases them primary oocytes - begin meiosis I and doesn’t complete it after puberty: once a month an egg grows: continues meiosis I produces secondary oocyte & 1 polar body  Oogenesis secondary oocyte stops in metaphase II and is released: if not penetrated by sperm meiosis is not completed and shedding of uterine line occurs if penetrated by sperm, meiosis is completed Note: the ruptured follicle is now known as the corpus luteum.  Hormone Regulation GnRH: from hypothalamus controls hormone release from anterior pituitary: FSH and LH FSH: triggers oogenesis & production of estrogen LH: triggers production of progesterone & estrogen & maintains the uterus  Hormone Regulation Estrogen Secondary sex characteristics  Menstrual Cycle Ovarian Cycle: Changes that occur in the ovaries Uterine Cycle: Changes that occur in the uterus Must be coordinated – average cycle is 28 days  Ovarian Cycle Ovarian Cycle 1. Follicular Stage: Follicle enlarges and oocyte matures 2. Ovulation: release of ovum 3. Corpus Luteum: a ruptured follicle  Uterine Cycle Uterine Cycle 1. Menstrual Phase 2. Proliferative/ Secretory Phases  9.8 Fertilization & Pregnancy Ovulation is typically day 14 of cycle Oocyte is viable 24 hrs. after it leaves the ovary. Sperm retain their fertilizing power within female reproductive tract up to 3 days after ejaculation. ("super sperm" are viable for 5 days.) Intercourse must occur no more than 5 days before ovulation and no later than 24 hrs. after the oocyte is ovulated Fertilization  Fertilization Sperm fuses to oocyte membrane and activates it (depolarizes) 1.) Triggers cortical reaction (exocytosis of enzymes) which inactivates sperm receptors & hardens zona pellucida 2.) completes meiosis II 3.) activates enzymes for mRNA for rapid protein synthesis male pronucleus fuses with female pronucleus = zygote Human Embryonic Development  Pre-Embryonic Development Cleavage: Rapid mitosis, little growth by 36 hrs. after fertilization, the 1st cleavage division produces 2 ID cells which divide to produce 4 cells then 8: eventually form solid ball of cells termed morula Pre-Embryonic Development  Implantation Trophoblast releases enzymes to digest endometrium Trophoblast forms chorionic villi which grow into endometrium  Implantation hCG: Human Chorionic Gonadotropin: secreted by the trophoblast prompts the corpus luteum to secrete progesterone hCG usually detectable in mothers blood by 3rd week of gestation hCG levels decline after 4 months Embryonic Development  Embryonic Development Gastrulation: cells move toward primitive streak (central line) produces 3 layered sheet of cells termed embryonic disc which will become the embryo Gastrulation Pregnancy Placenta  Fertilization & Pregnancy Gestation period: the time during which development occurs (280 days) First Trimester – Rudiments of all major organ systems appear Second Trimester – Development of organs and organ systems – Body shape and proportions change By end, fetus looks distinctively human Third Trimester – Rapid fetal growth and deposition of adipose tissue – Most major organ systems are fully functional  Fertilization & Pregnancy The First Trimester Most dangerous period in prenatal life 40% of conceptions produce embryos that survive past first trimester First Trimester  Twins Rates of Multiple Births Twins in 1 of every 89 births Triplets in 1 of every 892 (7921) births Quadruplets in 1 of every 893 (704,969) births  Activity 3 pg. 141 Comparing Mitosis & Meiosis Mitosis Meiosis Occurs in all cells beginning with zygote Produces four daughter cells Daughter cells are haploid Important for maintaining homeostasis Only occurs during formation of gametes Produces two daughter cells Goes through the phases once Introduces genetic variability Synapsis and crossing over occur Daughter cells are diploid Reduces chromosome number by half  Activity 3 Comparing Mitosis & Meiosis Mitosis Meiosis Occurs in all cells beginning with x zygote Produces four daughter cells x Daughter cells are haploid x Important for maintaining x homeostasis Only occurs during formation of x gametes Produces two daughter cells x Goes through the phases once x Introduces genetic variability x Synapsis and crossing over occur x Daughter cells are diploid x Reduces chromosome number by x half  Mitosis and Meiosis Lab Report 1. Why is mitosis critical for life? – Used for replacement of damaged and dying cells – Allows for growth of organism 2. What is the diploid number for human cells? – 46 3. Prophase—c; Prometaphase—e; Metaphase---d; Anaphase—b; Telophase—a 4. Differences between mitosis and meiosis – # of cells at end; function; genetic variation at end; number of cell/nuclear divisions; homologous chromosomes pair during meiosis 5. Similarities between mitosis and meiosis – Both start with diploid cells; DNA is replicated during Interphase