The Basis of Heredity

Principle of Dominance Tracked seventraits through seven generations of garden Peas. First cross from parent – Parental Generation The next cross – Filial Generation (FG1, FG2, FG3, FG4 FG5, FG6, FG7) Garden peas reproduce through self-pollination. This creates a pure copy of the plant, so that when Mendel wanted to isolate a trait, he could cross- pollinate and be sure that what he was observing was the isolated trait. Gregor Mendel Principle of Dominance

Offspring of cross-pollinated plants – Progeny Dominant Trait – when the combination of genes predominantly produces a specific characteristic (round seed) Recessive Trait – low probability of a trait developing (wrinkled seed) Allele – Alternate form of gene gene for seed colour – 2 alleles (1 for round and one for wrinkled) Dominant Allele – R Recessive Allele – r Two copies of a gene in a gene pair undergo Segregation during the formation of the sex cells.

Mendel’s Principle of Segregation Mendel cross-pollinated the parent plant to determine the seed (F1). Allowed that plant to grow and self-pollinate to observe transmission of trait to F2 generation F2 generation has a 3:1 ration (75% dominant, 25% recessive) Both alleles are the same – Homozygous Alleles are different – Heterozygous Complement of gene is Genotype, Physical expression is Phenotype Mendel’s Principle of Segregation

Homozygous – each gamete carries the same allele Heterozygous – each gamete could receive either allele