Genetics Fundamentals: Inheritance and Variation

📋 Course Outline

1. Single-gene inheritance variations
2. Protein function and dominance
3. Multiple alleles and phenotype diversity
4. Incomplete dominance
5. Codominance and ABO blood groups
6. Lethal alleles
7. Pedigrees and inheritance patterns
8. Product rule in genetics

📖 1. Single-gene inheritance variations

🔑 Key Concepts & Definitions

• Multiple allelism : Multiple allelism is when a gene locus has more than two possible alleles in a population.
• Incomplete dominance : Incomplete dominance is a single-gene pattern where the heterozygote shows an intermediate phenotype between the two homozygotes.
• Codominance : Codominance is a single-gene pattern where a heterozygote expresses both alleles simultaneously without an intermediate phenotype.
• Lethal alleles : Lethal alleles are gene variants whose homozygous state causes death, while the heterozygous state can be viable.
• Pedigrees : Pedigrees are family trees that track the segregation of a trait across multiple generations to infer inheritance patterns.

📝 Essential Points

• In a population, more than two alleles can exist at a single gene locus even though each individual carries only two alleles per gene.
• Many distinct phenotypes can arise from multiple alleles at one locus in the population.
• For interpretation, common phenotypic ratios include 3:1, 1:2:1, 2:1, and the “2:1” shift caused by lethal genotypes.

💡 Memory Hook