Genetics_SDH 2025 with link to video Posting

Genomics in Human Growth and Development

  • Speaker: Sandra Daack-Hirsch PhD, RN

  • Institution: The University of Iowa, College of Nursing

  • Term: Spring 2025

Genomic Terms

  • Human genome: The complete set of genes or genetic material present in a cell or organism.

  • Chromosomes: Molecules with a linear arrangement of genes; human cells contain 23 pairs of chromosomes.

  • DNA: The molecular structure that contains the instructions for directing cell activities.

    • Coding DNA: Sequences that code for proteins.

    • Non-coding DNA: Non-protein-coding regions involved in regulation and other functions.

  • Genes: Basic units of heredity; segments of DNA that contain coded information.

Genetic Terms

  • Allele: One of two or more forms of a gene or genetic locus.

  • Egg or Sperm: Each carries one allele for each gene.

  • Polymorphism: Sequence variation in DNA that occurs with at least 1% frequency in the population.

  • Mutation: Occurs when there is a rare variant present in less than 1% of the population.

Chromosomes

  • Humans have 23 pairs of chromosomes:

    • 22 pairs of autosomes

    • 1 pair of sex chromosomes (XX or XY).

  • Alterations: Can include changes in number (aneuploidy), portions of a chromosome being added or missing, and translocations (chromosomal parts being attached to others).

Genes Overview

  • Human genome contains about 21,000 genes.

  • These genes code for more than 100,000 proteins.

  • Composed of approximately 3 billion base pairs.

  • Genetic similarity: Humans are 99.9% genetically identical; only 0.1% of base pairs (around 3 million) differ between individuals.

Chromosome Variations

  • General Features:

    • Can lead to alterations in growth and development.

    • Neurological development may show delays.

    • May result in distinctive facial features and multiple anomalies.

Down Syndrome

  • A condition resulting from an extra chromosome 21.

  • Common characteristics include varying degrees of intellectual disability and recognizable features.

Gene Variations

  • Traditional Genetics: Focuses on relatively rare single gene disorders.

    • Single Gene Disorders: Can be classified as:

      • X-linked (e.g., Hemophilia)

      • Autosomal dominant (e.g., Achondroplasia)

      • Autosomal recessive (e.g., Tay Sachs, Cystic Fibrosis)

  • Genomics: Encompasses genetic variants, environmental risks, gene-gene, and gene-environment interactions impacting lifelong growth and development, as well as common diseases.

Cell Types

  • Germ Cells:

    • Sperm and ova; only cells capable of meiosis.

  • Somatic Cells:

    • All other body cells, providing structure and function to the body.

Fertilization

  • Process:

    • Two gametes (sperm and egg) fuse to form a zygote with 46 chromosomes.

  • The resulting zygote carries genetic information from both parents but is genetically unique.

Mutations at Fertilization

  • Inherited Mutations: Occur at the fertilization stage; examples include chromosomal disorders and single gene disorders.

  • De Novo Mutations: Genetic changes that neither parent possessed.

Post-Fertilization Mutations

  • Mosaicism:

    • Errors in cell division after fertilization, leading to mixed cell lines (normal and abnormal).

    • Can result in conditions like mosaic Down syndrome.

Cleavage

  • Begins one day after fertilization when the zygote divides into blastomeres.

  • Morula Stage: Approximately 16 cells.

  • Blastulation: Continues producing cells which form a blastula (128 cells).

Implantation

  • Occurs at day five post-fertilization, when the blastocyst attaches to the uterine lining, marking the start of pregnancy.

Gastrulation

  • Happens in the third week of development:

    • Cells migrate and form three germ layers:

      • Ectoderm: Develops into the nervous system and skin.

      • Endoderm: Forms digestive and respiratory systems.

      • Mesoderm: Gives rise to bones, muscles, and connective tissues.

Cell Differentiation

  • The process through which cells become functionally and structurally distinct.

    • Germ Cells: Oocytes and sperm.

    • Various other differentiated cells arise from primary germ layers.

Stages of Development

  1. Dividing Zygote, Implantation, Bilaminar Embryo

  2. Main Embryonic Period

  3. Fetal Period

  4. Embryonic and Fetal Development:

  • Key Points: Sensitivity to teratogenic factors varies with developmental stage, influencing congenital anomalies.

Human Genome Insights

  • Relationship between genetics and environment is complex (e.g., height experiment).

  • Genetic Determinism: Challenges the notion by emphasizing gene-environment interactions.

Experimental Model on Height

  • Modeling Height: A two-step process to understand how both genetic and environmental factors contribute to determining height.

    • Step 1: Establish genetic height using a coin-toss method.

    • Step 2: Adjust genetic height based on environmental influences.

Epigenetics

  • The study of changes in gene expression not caused by alterations in the DNA sequence.

  • Regulation of gene expression starting from conception influences the entire lifespan.

Environment vs Genetics

  • Genetics isn't Everything: Environmental factors and influences from family play significant roles in development.

  • Siblings Comparison: Research highlights that while physical traits show similarities, personality differences may not correlate significantly.

Theories on Genetic Influence

  • Three Theories:

    • Principle of Divergence (Dr. Frank Sulloway)

    • Developmental (Dr. Susan McHale)

    • Comparison Machines (Dr. Susan McHale)

Genetic Research at the College of Nursing

  • Focused on understanding genetic influences on health and disease outcomes among diverse populations.

  • Notable researchers and their focal areas include:

    • Sue Gardner: Microbiome and diabetic foot ulcer

    • Sandy Daack-Hirsch: Genetic literacy and healthcare implications

    • Stephanie Gilbertson-White: Contextual genetic factors in cancer symptoms

    • Catherine Cherwin: Influence of gut microbiome on cancer.

Questions/Answers

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