Intro To Mendelian Genetics

1. Introduction to Mendelian Genetics

• Basics of inheritance and genetic terminology.

• Example: Cystic Fibrosis as a trait passed through generations.

  • Parents: Both carriers of the CF gene mutation.

  • Possible child outcomes:

    • Child with Cystic Fibrosis (CF).

    • Child carriers of CF gene mutation.

    • Child without CF.

2. Learning Outcomes

• Understanding heredity:

  • Transmission of traits from parents to offspring (anatomical, physiological, behavioral).

• Importance of model systems in advancing genetics research.

• Significance of Gregor Mendel's choice of pea plants as a model system for investigating inheritance.

• Grasp terminology relevant to Mendelian genetics.

3. Use of Model Organisms

• Researchers select model organisms to expedite scientific discoveries.

  • Benefits:

    • Advances in agricultural, environmental, and medical science.

4. Gregor Mendel's Choice of Pea Plants

• Peas as a model organism due to:

  • Agricultural and nutritional relevance.

  • Easy seed procurement and inexpensive large-scale growth.

  • Rapid growth rates and brief reproductive cycles.

  • Manageable sexual reproduction processes.

5. Understanding Traits

• Traits:

  • Anatomical, behavioral, or physiological characteristics inherited from parents.

• Definition of Locus:

  • A "unit of heredity" on a chromosome that regulates traits.

  • Contains genes and regulatory nucleotide sequences affecting gene expression.

6. Ploidy and Chromosome Sets

• Ploidy: Number of chromosome sets in a eukaryotic nucleus.

  • Haploid (N) vs. Diploid (2N) e.g., human gametes with 23 chromosomes.

  • Polyploidy: more than two sets of chromosomes.

    • Examples:

      • Common wheat (6N), Tobacco (4N), Strawberry (8N), etc.

7. Alleles

• Alleles: Different forms of a gene.

  • Unique nucleotide sequences that impart distinct genetic information.

  • Formed by mutations in existing alleles.

8. Genotype

• Genotype: The two alleles present in a diploid individual.

  • Affects individual characteristics and has medical relevance.

  • Examples:

    • Homozygous alleles from both parents vs. different alleles from each parent.

9. True Breeding Traits

• True breeding refers to traits that remain constant through generations with homozygous parents.

  • Example of homozygous AA genotypes ensuring all offspring inherit the same allele.

10. Phenotype

• Phenotype: Observable characteristics resulting from genotype and environmental interactions.

  • Example: Identical genotypes yielding different phenotypes due to environmental conditions (e.g., soil pH affecting flower color).

11. Environmental Influence on Phenotype

• Variation in environmental conditions can affect the phenotype of genetically identical individuals.

  • Factors: Womb conditions, postpartum environment.

12. Impact of Environmental Factors on Children

• Parental care has significant effects on children's brain size, activity, and behavior.

  • Increased care correlates with positive developmental outcomes.

  • Lack of care can lead to negative developmental effects.

13. Dominant and Recessive Traits

• Dominant phenotype expressed in heterozygotes or homozygotes.

  • Example: Purple flowers dominate over white flowers in pea plants.

14. Punnett Square as a Tool

• Tool for visualizing and predicting offspring genotypes and phenotypes based on parental alleles.

• Demonstrates genotype ratios from dominant/recessive allele interaction.

15. Chromosomes in the Nuclear Genome

• Autosomes: Chromosomes numbered by descending length.

  • X and Y chromosomes are sex chromosomes.

  • Males are hemizygous for genes on X and Y.

16. SRY Gene

• Located on the Y chromosome; determines male sex.

  • Encodes a protein necessary for male gonad development.

  • Sex of the child is determined by the sex chromosome from the sperm that fertilizes the egg.

17. Study Guide Questions

• Identify model systems suitable for studying: human brain, immune system, crop yield.

• Define key genetic terms: Allele, Locus, Ploidy, etc.

• Discuss genetic variations and factors influencing phenotype.

• Understand the role of autosomes and sex chromosomes in determination of traits.

  Study Guide Answers

  1. **Identify model systems suitable for studying:** - **Human Brain**: Non-human primates (e.g., monkeys) for neurological studies; Rodent models (e.g., mice, rats) for genetic manipulation studies; Human organoids grown from stem cells for in vitro studies. - **Immune System**: Mice due to similarities with human immune responses; Zebrafish for studying immune development; Non-human primates for disease and vaccine studies. - **Crop Yield**: Arabidopsis thaliana as a model plant; Maize for agricultural genetics; Rice for studying yield traits.

  2. **Define key genetic terms:** - **Allele**: Different forms of a gene that produce distinguishable phenotypic effects. - **Locus**: The specific location of a gene on a chromosome. - **Ploidy**: The number of sets of chromosomes in a cell; commonly haploid (N) or diploid (2N).

  3. **Discuss genetic variations and factors influencing phenotype:** Genetic variations arise from mutations, recombinations, and gene flow; Environmental factors, such as nutrient availability and temperature, can influence phenotype.

  4. **Understand the role of autosomes and sex chromosomes in determination of traits:** - **Autosomes**: Non-sex chromosomes that determine most traits. - **Sex Chromosomes**: X and Y chromosomes determine sex and influence sex-linked traits; Males are hemizygous for X and Y-linked genes, while females have two X chromosomes, affecting trait expression differently.