Punnett Squares MT Sexual Reproduction New terms Homozygous

Punnett Squares MT: Sexual Reproduction

New terms Homozygous: same alleles for a trait – Ex: AA or aa Heterozygous: different alleles for a trait – Ex: Aa

Practice AA = homozygous dominant aa = homozygous recessive Aa = heterozygous Tt = ? TT = ? BB = ? Bb = ? bb = ? Hh = ? hh = ?

New terms Dominant: phenotype will show up; represented with a capital letter – Ex: A Recessive: phenotype will not show up if there is a dominant allele around – Ex: a

Steps to Punnett Squares 1. Find the parents’ genotypes 2. Find the possible alleles of the gametes 3. Set up Punnett Square 4. Find allele combinations of possible offspring 5. Find genotypes and phenotypes of possible offspring

Example Having brown eyes is dominant over blue eyes. A man that is heterozygous for brown eyes mates with a woman that is homozygous for brown eyes. What are the possible offspring combinations?

Step 1: Parents’ Genotypes Dad’s genotype: Bb Mom’s genotype: BB

Step 2: Alleles for gametes Dad’s gametes: B or b Mom’s gametes: B or B

Step 3: Set up Punnett Square Bb x BB B b

Step 4: Fill out Punnett Square Bb x BB B b B BB Bb

Step 5: Find out genotypes and phenotypes Bb x BB B B BB b Bb Genotypes: BB = 2/4 = 50% Bb = 2/4 = 50% Phenotypes: B BB Bb Brown = 4/4 = 100% Blue = 0/4 = 0%

Example Having brown eyes is dominant over blue eyes. A man that is heterozygous for brown eyes mates with a woman that is homozygous for blue eyes. What are the possible offspring combinations?

Bb x bb B b b Bb bb

Bb x BB B b Bb b bb Genotypes: Bb = 2/4 = 50% bb = 2/4 = 50% Phenotypes: b Bb bb Brown = 2/4 = 50% Blue = 2/4 =50%