Punnett Squares

B stands for Brown Hair b stands for Blond Hair Capital Letters mean traits are DOMINANT Lower-Case Letters mean traits are recessive

Heterozygous = Having 2 different Alleles (1 dom. + 1 rec.) [Bb] Homozygous = Having 2 of the same Allele (2 dom. or 2 rec.) [BB] or [bb]

If you have… BB = Brown Hair Bb = Brown Hair bb = Blond Hair

Dad gives you one Allele Bb Mom gives you one Allele Bb BB Bb Bb bb

Easier Way…

Make a window…

Dad’s Traits B b B Mom’s Traits b

Dad’s Traits B b B B B Mom’s Traits b

Dad’s Traits B b B B B B b Mom’s Traits b

Dad’s Traits B b B B B B b Mom’s Traits b B b

Dad’s Traits B b B B B B b Mom’s Traits b B b b b

Punnett Square B b B B B B b b B b b b

What % have brown hair? What % are Homozygous? B B B b B b b b

what the trait looks like Genotype what the genes are [“bb” or “Bb”] Phenotype what the trait looks like [long nose or 6 fingers]

Things to Know Dominant Allele Recessive Allele Heterozygous Homozygous (Dom. or Rec.) Punnett Square “Carrier” – Bb – Carries recessive gene and can pass it along without showing trait I’ll make questions using this vocabulary. I promise.