Early Embryology to Gastrulation
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Early Embryology to Gastrulation

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Questions and Answers

During which phase of cell division does DNA first replicate?

  • M phase
  • G1 phase
  • G2 phase
  • S phase (correct)

    • The amount of DNA in a germ cell is doubled during meiosis.

    False

    What term describes the ball of cells formed after fertilization?

    morula

    In early embryonic development, the process that initiates differentiation is called __________.

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

    Match the following stages of prenatal development with their descriptions:

    <p>Stage 1 = Cellular proliferation Stage 2 = Morphogenesis Stage 3 = Growth and maturation</p> Signup and view all the answers

    What is the term used to describe the formation of the trilaminar embryo?

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

    The sex chromosomes in humans are designated as X and Y.

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

    What are the two types of chromosomes found in human somatic cells?

    <p>Autosomes and sex chromosomes</p> Signup and view all the answers

    Fertilization leads to the formation of a __________.

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

    Which stage of human development involves the earliest embryonic development from fertilisation to gastrulation?

    <p>Weeks 1-3</p> Signup and view all the answers

    Name one congenital defect associated with abnormal embryological development.

    <p>Down syndrome</p> Signup and view all the answers

    Match the following terms with their definitions:

    <p>Spermatozoa = Male reproductive cell Haploid = A cell containing one set of chromosomes Meiosis = Cell division that produces gametes Mitosis = Cell division for growth and repair</p> Signup and view all the answers

    Meiosis is a process that results in the formation of __________ cells.

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

    What effect does hypermethylation of CpG islands have on gene transcription?

    <p>Inhibits gene transcription</p> Signup and view all the answers

    Histone modification does not affect gene expression.

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

    What is the main difference between genetics and epigenetics?

    <p>Genetics involves the DNA sequence inherited, while epigenetics involves chemical modifications that affect gene expression.</p> Signup and view all the answers

    The addition of a methyl group to ______ is a process known as DNA methylation.

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

    Match the types of epigenetic changes with their descriptions:

    <p>DNA Methylation = Covalent modification of DNA affecting gene transcription Histone Modification = Chemical changes to histones that regulate transcription Non-coding RNA = Regulatory RNAs that do not encode proteins CpG Islands = Regions rich in CpG sites often found in promoters</p> Signup and view all the answers

    What is the name of the structure formed by the differentiation of the morula?

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

    The ectoderm layer is formed from cuboidal cells.

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

    What are the three primary germ layers formed during gastrulation?

    <p>Ectoderm, mesoderm, endoderm</p> Signup and view all the answers

    During gastrulation, the _____ streak is formed, facilitating the transition from a bilaminar to a trilaminar disc.

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

    Which of the following is NOT a fate of the ectoderm?

    <p>Inner linings of digestive tube</p> Signup and view all the answers

    Down syndrome is caused by a trisomy affecting chromosome 21.

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

    What is the function of the notochord formed during gastrulation?

    <p>To establish the axis of the embryo and provide structural support.</p> Signup and view all the answers

    The _____ layer of the bilaminar disc is responsible for forming the amniotic cavity.

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

    Match the following cell types with their corresponding derivatives:

    <p>Ectoderm = Nervous system Mesoderm = Muscles Endoderm = Inner lining of the digestive tract Epidermis = Skin</p> Signup and view all the answers

    What happens if a gamete with 24 chromosomes fuses with a normal gamete during fertilization?

    <p>It results in a zygote with 47 chromosomes.</p> Signup and view all the answers

    Which condition is characterized by an extra X chromosome in boys?

    <p>Klinefelter syndrome</p> Signup and view all the answers

    Turner syndrome occurs when there is an absence of one X chromosome in females.

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

    What are common clinical features of Down syndrome?

    <p>Facial clefts, a shortened palate, protruding and fissured tongue, and delayed eruption of teeth.</p> Signup and view all the answers

    Monosomy of the X chromosome is a condition associated with ______ syndrome.

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

    What is a common situation in which autosomal dominant inheritance occurs?

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

    Genetic defects are only caused by environmental factors.

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

    Match the following genetic conditions with their inheritance pattern:

    <p>Achondroplasia = Autosomal dominant Cystic fibrosis = Autosomal recessive Dentinogenesis imperfecta = Autosomal dominant Chondroectodermal dysplasia = Autosomal recessive</p> Signup and view all the answers

    Epigenetics studies how behaviors and environment can cause ______ that affect gene expression.

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

    Study Notes

    Early Embryology and Gastrulation

    • Embryonic Development Stages: Covers development from fertilization to gastrulation (weeks 1-3).
    • Defects in Development: Discusses known defects like Down’s syndrome and Turner syndrome.
    • Epigenetic Influence: Genetic and epigenetic processes play key roles in early embryonic development.

    Importance of Studying Embryology

    • Head and Neck Development: Understanding embryology is critical for comprehending facial and dental development origins.
    • Congenital Defects: Provides insights into causes of congenital defects in related tissues.
    • Regenerative Medicine: Relevant for understanding mechanisms in regenerative medicine and dentistry.

    Germ Cell Formation and Fertilization

    • Somatic Cells: Human somatic cells have 46 chromosomes comprising 44 autosomes and 2 sex chromosomes (X & Y).
    • Haploid and Diploid: Gametes are haploid (23 chromosomes); fertilization creates a diploid zygote (46 chromosomes).
    • Meiosis vs. Mitosis: Meiosis results in gametes; mitosis results in somatic cell division after DNA replication.

    Prenatal Development Stages

    • Stage 1 (0-4 weeks): Involves cellular proliferation and migration.
    • Stage 2: Morphogenetic processes begin.
    • Stage 3: Entails growth and maturation.

    Induction, Competence, and Differentiation

    • Patterning: Involves initial axial specification and segmentation.
    • Induction: Signals cells to differentiate; key agents include homeobox genes and growth factors.

    Week 1: From Fertilization to Blastocyst

    • Initial Cell Division: The fertilized egg becomes a morula through rapid divisions.
    • Blastocyst Formation: Cells reorganize into the blastocyst, consisting of the embryoblast and trophoblast.

    Week 2: Implantation of Blastocyst

    • Bilaminar Disc: Formation of a two-layered structure (epiblast and hypoblast) occurs around day 8 of gestation.

    Week 3: Gastrulation

    • Trilaminar Disc Formation: Converts the bilaminar disc into a structure with three primary germ layers: ectoderm, mesoderm, and endoderm.
    • Primitive Streak Formation: Initiates extensive cellular rearrangement and migration.

    Fate of Germ Layers

    • Ectoderm: Forms nervous system, sensory organs, epidermis, and pituitary gland.
    • Mesoderm: Develops into notochord, skeleton, muscles, circulatory system, and dermis.
    • Endoderm: Forms inner linings of digestive and respiratory tracts, pancreas, and liver.

    Defects in Embryonic Development

    • Chromosomal Abnormalities: Meiosis malfunction can lead to congenital anomalies affecting head and neck regions.
    • Down Syndrome: Result of trisomy 21; characterized by facial clefts and delayed tooth eruption.
    • Turner Syndrome (X0): Missing X chromosome leads to short stature and various clinical features.
    • Klinefelter Syndrome (XXY): Extra X chromosome results in taller stature and gynecomastia.

    Genotype vs. Phenotype

    • Genetic Defects: Refer to abnormalities in genetic makeup.
    • Genotype: Underlies characteristics affected by environmental context.
    • Phenotype: Represents observable traits resulting from development.

    Genetics vs. Epigenetics

    • Genetics: Examines genes and hereditary information.
    • Epigenetics: Involves how behaviors and environment can modify gene expression without changing the DNA sequence.

    Mechanisms of Epigenetics

    • DNA Methylation: Addition of methyl groups to cytosines affects gene transcription; hypermethylation decreases transcription, while hypomethylation increases it.
    • Histone Modification: Changes to histones regulate transcription factor activity.
    • Non-coding RNA: Includes siRNA and miRNA, which regulate gene expression and differentiation.

    Summary of Differences:

    • Genetics vs. Epigenetics: Genetics refers to inherited traits; epigenetics concerns gene activity regulation and environmental influences.

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    Related Documents

    Embryology Series (1) Early embryology (to gastrulation) - Dr Wai Ling Kok (2024-25).pptx

    Description

    This quiz explores the earliest stages of embryonic development, focusing on the period from fertilization to gastrulation. Key events such as gametogenesis, blastocyst formation, and the formation of the trilaminar embryo will be examined in detail. Prepare to delve into human developmental processes occurring in the first three weeks.

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