Reproduction and Genetics Dominant and Recessive Genes I. Monohybrid Crosses  A. Three class genotypes – 1. Homozygous Dominant = BB – 2. Homozygous Recessive = bb – 3. Heterozygous = Bb   B. B = Black & b = Red C. Six possible crosses: BB x BB, BB x Bb, BB x bb, Bb x Bb, Bb x bb, bb x bb I. Predicting Ratio’s    Homozygous x Homozygous A. Genotype B B – 2. Results in a homozygous dominant zygote B BB BB – Phenotype: – 1. Each parent can only contribute a dominant gene B BB BB B. BB x BB I. Predicting Ratios   B. Homozygous x Homozygous . bb x bb - All will be red  Genotypic Ratio b b b bb bb b bb bb – 4bb : 0  Phenotypic Ratio – 4 red coats : 0 black coats I. Six Fundamentals Types of Mating   Homozygous x Homozygous F. BB x bb – Genotypic ratio:   0BB : 4Bb All offspring will be heterozygous – Phenotypic ratio: 4 black coat : 0 red coat B B b Bb Bb b Bb Bb II. Predicting Ratios Homozymous x Heterozygous  E. BB x Bb B B B BB BB b Bb Bb – 1. Genotypic Ratio  2 BB : 2 Bb – 2. Phenotypic Ratio  a) 4 Black color III. Predicting Ratio’s  G. Bb x Bb B b B BB Bb b Bb bb – 1. Phenotypic Ratio  a) 3 black to 1 red or 3:1 – 2. Genotypic Ratio  a) 1BB: 2Bb: 1bb IV. Predicting Ratio  H. Bb x bb b b B Bb Bb b bb bb – 1. Genotypic Ratio  a) 2Bb: 2bb – 2. Phenotypic Ratio  a) 2 black to 2 red II. Multiple Gene Pairs  A. Mating – 1. B = Black & b = Red – 2. P = Polled & p = polled  B. Bull – 1. BbPp  C. Cow – 1. BbPp  D. What will the phenotypic & genotypic ratios be? II. Multiple Gene Pairs PB Pb pB pb PB PPBB PPBb PpBB PpBb Pb PPBb PPbb PpBb Ppbb pB PpBB PpBb ppBB ppBb pb PpBb Ppbb ppBb ppbb II. Multiple Gene Pairs  E. Genotypic Ratio – 1. 1 PPBB: 2 PPBb: 1 PPbb: 2 PpBB: 4 PpBb: 2 Ppbb: 2 ppBb: 1ppbb  F. Phenotype – 1. – 2. – 3. – 4. 9 polled and black 3 polled and red 3 horned and black 1 horned and red