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