Post on 20-Jan-2016
Rat Genetics
Male Rat (Dad)
• Phenotype– Black Hair
• Genotype– BB / Bb
Female Rat (Mom)
• Phenotype– Gray (shade of
Black) Hair Coat
• Genotype– 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
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
2nd Mating / F2 Generation Offspring
• phenotype– 75% Black Hair Coat– 25% White Hair Coat
• Genotype– 75% BB / Bb– 25% bb
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