Rat Genetics

Male Rat (Dad) Phenotype Black Hair Genotype BB / Bb

Female Rat (Mom) Phenotype Genotype Gray (shade of Black) Hair Coat BB / Bb

Vocabulary Terms Heterozygous: The 2 alleles for the trait are different ex. Bb 1 dominate & 1 recessive Homozygous: The 2 alleles for the trait are the same ex. BB or bb 2 dominant or 2 recessive Phenotype: Physical appearance Genotype: Genetic traits (BB /Bb / bb)

What will their offspring’s phenotype and genotype be if female is heterozygous dominant for black hair and the male is homozygous for black hair? Female Male Bb -BB Offspring Black Hair White Hair Homozygous Heterozygous B b b B B B B 100% 0% 50% B B B b B 50%

1st Mating Offspring / F1 Generartion (babies) 9 lived Phenotype 100% Black Hair Coat Genotype 100% BB / Bb

What will their offspring’s phenotype and genotype be if male and female is heterozygous dominant for black hair? Female Male Bb -Bb Offspring Black Hair White Hair Homozygous Dom. Rec. Heterozygous B b B B B B b 75% 25% b B b b b 25% 25% 50%

2nd Mating / F2 Generation Offspring phenotype 75% Black Hair Coat 25% White Hair Coat Genotype 75% BB / Bb 25% bb

Both Female (mom) and Male (dad) genotype has to be.. So based on the phenotypes of the second mating offspring we now know…. Both Female (mom) and Male (dad) genotype has to be.. Bb Heterozygous Dominant for black hair

Your Turn: Name: ___________ Per___ What would happen if you breed the white homozygous (bb) rat to an black homozygous rat (BB)? Phenotype black ________% white ________ % Genotype ___ ______% Draw/Color picture to show Phenotype of offspring on back of this sheet