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
Dividing Zygote, Implantation, Bilaminar Embryo
Main Embryonic Period
Fetal Period
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.