Mendelian Genetics Lecture Notes

Introduction to Mendelian Genetics

Presenter: Mr. Andersen
Named After: Gregor Mendel
- Contributions to genetics
- Worked with pea plants to discover genetic principles
Comparison: Charles Darwin was known in his time; Mendel died in obscurity
Modern Synthesis: Combination of Mendel's and Darwin's theories

Pea Plant Crosses:
- Mendel transferred pollen using a paintbrush
- Pea plants: fast-growing, multiple characteristics
- Identified two key genetic principles:
  - Law of Segregation
  - Law of Independent Assortment

Law of Segregation:
- Alleles separate during gamete formation
- Probability of receiving a specific allele is 50%
- Demonstrated using a coin flip analogy
Law of Independent Assortment:
- Genes for different traits are inherited independently
- Example: Hitchhiker's thumb and attached earlobe do not affect each other
- Exceptions: Linked genes (e.g., red hair and freckles)

Punnett Squares:
- Tool for predicting genetic outcomes
- 3:1 ratio of dominant to recessive traits observed
- Example: Purple (dominant) vs. white (recessive) flowers

Coin Flip Probability:
- 1/2 probability for heads or tails regardless of previous results
Heterozygous vs. Homozygous Classification:
- Homozygous dominant: e.g., RR
- Heterozygous: e.g., Rr (also called hybrids)
Phenotype Determination:
- Genotype: Genetic makeup (e.g., Yy)
- Phenotype: Physical appearance (e.g., yellow)
Cross Probability Problems:
- Monohybrid crosses using Punnett squares
- Example: Round (R) vs. wrinkled (r) seeds

Huntington's Disease:
- Causes degeneration of nerve fibers, leading to serious symptoms
- Dominant genetic disorder
- Example pedigree analyzed
Ethical Considerations:
- Genetic testing implications
- Questions about knowing one's genetic fate
- Insurance concerns