Understanding Mendelian Genetics
Quick Answer: Mendelian genetics describes how traits are inherited from parents to offspring through genes. Mendel's laws of segregation and independent assortment explain monohybrid (3:1) and dihybrid (9:3:3:1) ratios.
Key Concepts
Law of Segregation: Allele pairs separate during gamete formation. Law of Independent Assortment: Genes for different traits assort independently. Dominant allele masks recessive in heterozygous condition.
Solved Examples
Gametes: T,t and T,t
Offspring: TT, Tt, Tt, tt
Phenotype: 3 tall : 1 dwarf
Genotype: 1:2:1
Gametes: RY,Ry,rY,ry
Phenotype: 9:3:3:1
Round Yellow: 9/16
Gametes: T,t and t
Offspring: Tt, tt
Ratio: 1 tall : 1 dwarf
Reveals unknown genotype
FAQs
Genotype is the genetic makeup (e.g., TT, Tt, tt). Phenotype is the physical expression (e.g., tall or dwarf). Dominant alleles determine phenotype in heterozygotes.
Because the recessive parent only contributes recessive alleles, the offspring's phenotype directly reveals the unknown parent's genotype. This is how we determine if a dominant phenotype is homozygous or heterozygous.
Alleles of different genes segregate independently during gamete formation, provided the genes are on different chromosomes. This leads to new combinations of traits.