Basic Genetic Principles

Basic Genetic Principles

Mendel's Cross (Pea Plant Height) P1 Generation F1 Generation F2 Generation heterozygous phenotypes genotypes homozygous

F1 (heterozygous) Cross F1 Cross Tall Tall Tt x Tt Punnett Square F2 Generation 25 % TT 25 % Tt 25 % tT 25 % tt 75 % tall 25 % short

Punnett Squares R – round r - wrinkled Round (Rr) x Round (Rr) Heterozygous Cross

Pedigrees

Basic Mendelian Genetic Concepts Rule of Dominance Law of Segregation • For any Given Trait, an Individual has 2 Alleles (pair of genes) • Only 1 Allele of the Pair is Expressed • When Heterozygous, the Expressed Allele is Dominant, the “Hidden” Allele is Recessive • An Individual Can Only Pass on 1 Allele (one of the pair) to the Next Generation • A Recessive Allele can only be Expressed when Homozygous • Alleles Segregate During Gamete Formation

Which Color is... Dominant? Recessive? Which Parent is... Heterozygous? Homozygous?

Round & Yellow Rr Yy Round & Yellow Rr Yy Dihybrid Cross X • 9 round & yellow • 3 wrinkled & yellow • 3 round & green • 1 wrinkled & green 75 % round 25 % wrinkled 75% yellow 25% green Law of Independent Assortment The Inheritance of one trait does not effect the inheritance of another trait

Dominant Allele Recessive Allele

Human Traits

Basic Genetic Principles