Introduction to Medical Embryology
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Questions and Answers

What occurs during synapsis in meiosis I?

  • Crossover segments are exchanged.
  • DNA replication takes place.
  • Sister chromatids separate.
  • Homologous chromosomes pair up. (correct)

    • What structure is formed by the pairing of homologous chromosomes?

  • Sister chromatid
  • Chiasma (correct)
  • Chromatid
  • Centromere

    • What is the role of crossover during meiosis I?

  • It replicates centromeres.
  • It prevents chromatid separation.
  • It increases genetic variability. (correct)
  • It creates identical daughter cells.

    • During which phase do homologous chromosomes separate?

    <p>Anaphase I</p> Signup and view all the answers

    How many secondary spermatocytes are produced after meiosis I in males?

    <p>Two</p> Signup and view all the answers

    What occurs during meiosis II?

    <p>Sister chromatids are separated.</p> Signup and view all the answers

    What is true about DNA replication in meiosis II?

    <p>It does not occur at all.</p> Signup and view all the answers

    How many crossovers typically occur during each meiotic I division?

    <p>30 to 40</p> Signup and view all the answers

    What is gastrulation primarily involved in?

    <p>Arrangement of cells into three primary germ layers</p> Signup and view all the answers

    What defines a diploid cell in humans?

    <p>Contains 46 chromosomes in 23 homologous pairs</p> Signup and view all the answers

    What occurs during the formation of the tube-within-a-tube body plan?

    <p>Body folding of the embryonic disc into C-shaped structure</p> Signup and view all the answers

    How many genes are approximately found on human chromosomes?

    <p>23,000</p> Signup and view all the answers

    What characterizes linked genes?

    <p>Tend to be inherited together</p> Signup and view all the answers

    Which condition is an example of aneuploidy?

    <p>Cell with an extra chromosome (Trisomy)</p> Signup and view all the answers

    What is NOT a characteristic of euploid cells?

    <p>Contains an irregular chromosome number</p> Signup and view all the answers

    What does 'C value' refer to in genetics?

    <p>The number of double-stranded DNA copies in the nucleus</p> Signup and view all the answers

    What is the primary stage at which most primary oocytes remain arrested before puberty?

    <p>Prophase of meiosis I</p> Signup and view all the answers

    At what stage of prenatal development does the total number of germ cells in the ovary reach its maximum?

    <p>Fifth month</p> Signup and view all the answers

    During which phase do most oocytes become atretic during childhood?

    <p>Prophase of meiosis I</p> Signup and view all the answers

    What is the estimated range of primary oocytes present at birth?

    <p>700,000 to 2 million</p> Signup and view all the answers

    What defines a primordial follicle?

    <p>A primary oocyte surrounded by a single layer of flat epithelial cells</p> Signup and view all the answers

    What initiates the process of cell death among oogonia and primary oocytes?

    <p>Seventh month of prenatal development</p> Signup and view all the answers

    How long can some dormant oocytes remain in the diplotene stage before ovulation?

    <p>40 years or more</p> Signup and view all the answers

    Which type of cells surround the clusters of oogonia during development?

    <p>Follicular cells</p> Signup and view all the answers

    What is the purpose of mitosis?

    <p>To create two genetically identical daughter cells</p> Signup and view all the answers

    At which stage of mitosis do chromosomes first become distinguishable?

    <p>Prometaphase</p> Signup and view all the answers

    How many chromosomal sets are present in diploid cells before cell division?

    <p>4C</p> Signup and view all the answers

    What is the main outcome of meiosis?

    <p>Reduction of chromosome number to haploid</p> Signup and view all the answers

    During which phase do the chromatids migrate to opposite poles of the spindle?

    <p>Anaphase</p> Signup and view all the answers

    What restores the chromosome structure after mitosis concludes?

    <p>Reformation of the nuclear envelope</p> Signup and view all the answers

    What initiates the formation of the mitotic spindle?

    <p>Microtubule attachment to centromeres</p> Signup and view all the answers

    What differentiates haploid cells from diploid cells?

    <p>Haploid cells contain a single set of chromosomes</p> Signup and view all the answers

    What is the primary focus of embryology?

    <p>The study of prenatal developmental events</p> Signup and view all the answers

    Why is studying embryology important for physicians?

    <p>It allows for accurate patient advice on reproductive issues.</p> Signup and view all the answers

    What percentages of live-born children are likely to have significant malformations?

    <p>3-4%</p> Signup and view all the answers

    What are the two main periods of human embryology?

    <p>Embryonic and Fetal</p> Signup and view all the answers

    What process describes the conversion of germ cells into gametes?

    <p>Gametogenesis</p> Signup and view all the answers

    What is the primary event that follows fertilization?

    <p>Formation of the zygote</p> Signup and view all the answers

    What characterizes the embryonic period of human development?

    <p>Rapid changes and development</p> Signup and view all the answers

    Which of the following is NOT a phase of human embryology?

    <p>Gestation</p> Signup and view all the answers

    Study Notes

    Introduction to Medical Embryology

    • Embryology studies developmental events before birth.
    • Understanding embryology is crucial due to the incidence of birth defects (3-4% of live-born children).
    • Knowledge aids in comprehending adult anatomy and connections between basic and clinical sciences.

    Periods and Phases of Human Embryology

    • Embryonic Period: First 8 weeks post-fertilization marked by rapid changes.
    • Fetal Period: From the 9th week to birth; characterized by fetal growth and organ maturation.
    • Key Phases:
      • Gametogenesis: Formation of male (sperm) and female (egg) gametes.
      • Fertilization: Fusion of gametes to form the zygote.
      • Cleavage: Rapid cell divisions post-fertilization.
      • Gastrulation: Formation of three primary germ layers (ecto-, meso-, endoderm) and body axes.
      • Organogenesis: Development of organs and organ systems.

    Chromosome and Gene Basics

    • Humans possess approximately 23,000 genes across 46 chromosomes (23 pairs).
    • Chromosomes include 22 pairs of autosomes and one pair of sex chromosomes (XX = female, XY = male).
    • Ploidy indicates the number of chromosome sets: somatic cells (diploid, 2N) have 46 chromosomes, while gametes (haploid, 1N) have 23.

    Mitosis

    • Mitosis divides one cell into two genetically identical daughter cells, preserving the chromosome number.
    • Phases include:
      • Prophase: Chromosomes condense & become visible; each chromosome has two chromatids.
      • Metaphase: Chromosomes align at the equatorial plane, connected by microtubules.
      • Anaphase: Chromatids separate and move to opposite poles.
      • Telophase: Chromosomes de-condense, nuclear envelope reforms, and cytokinesis occurs.

    Meiosis

    • Meiosis produces gametes through two divisions: Meiosis I and Meiosis II, reducing chromosome number to haploid (23).

    • Meiosis I:

      • Homologous chromosomes undergo DNA replication, then align in pairs (synapsis).
      • Chiasma formation allows for genetic recombination (crossovers), enhancing genetic diversity.
      • Results in two daughter cells that are secondary spermatocytes in males and a secondary oocyte with a first polar body in females.

    • Meiosis II:

      • Sister chromatids are separated without prior DNA replication.
      • Final stages result in four haploid gametes from one original germ cell.

    Oogenesis

    • Oogonia proliferate by mitosis, with a maximum of about 7 million germ cells by the fifth month of prenatal development.
    • Most oogonia degenerate by the seventh month; surviving primary oocytes enter prophase of meiosis I and remain arrested until puberty.
    • At birth, 700,000 to 2 million primary oocytes are present, with approximately 400,000 by puberty; fewer than 500 are ovulated during reproductive years.

    Conclusion

    • Understanding gametogenesis, embryology phases, and cell division processes is fundamental for medical studies and practices, aiding in addressing reproduction-related clinical issues.

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    Medical Embryology Lecture 1 - Introduction to Gametogenesis (PDF)

    Description

    This quiz explores the fundamental concepts of medical embryology, covering periods and phases of human development before birth. You'll learn about gametogenesis, fertilization, and key developmental milestones like gastrulation and organogenesis. Understanding these processes is vital for linking embryology to adult anatomy and clinical practice.

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