Overview

This topic explores how traits are passed from one generation to the next through the laws of genetics. It introduces Mendel’s foundational work, modern extensions, and how patterns of inheritance help explain genetic variation in populations.

Key Concepts and Structures

• Genes and Alleles: Genes are units of heredity. Each gene can exist in different forms called alleles. Individuals inherit two alleles for each gene, one from each parent.
• Dominant and Recessive: A dominant allele masks the effect of a recessive one in a heterozygous genotype (e.g., Aa).
• Genotype vs. Phenotype: Genotype is the genetic makeup (e.g., Bb); phenotype is the observable trait (e.g., brown eyes).
• Mendel’s Laws:
  • Law of Segregation: Each gamete gets one allele for each gene.
  • Law of Independent Assortment: Genes for different traits segregate independently during gamete formation.
• Monohybrid and Dihybrid Crosses: Used to predict the probability of inheriting single traits (monohybrid) or two traits (dihybrid) using Punnett squares.
• Incomplete Dominance and Codominance: In incomplete dominance, the heterozygote has a blend (e.g., red + white = pink); in codominance, both alleles are expressed (e.g., AB blood type).
• Sex-Linked Traits: Traits controlled by genes on sex chromosomes (e.g., color blindness on the X chromosome). Males are more likely to express X-linked recessive traits.
• Pedigrees: Diagrams used to track inheritance patterns through generations, often used to assess genetic disorders.
• Mutations and Genetic Variation: Mutations are changes in DNA that may be inherited. They contribute to genetic diversity in populations.
• Probability in Genetics: Used to predict outcomes of genetic crosses and explain variation in offspring.

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