Probability and Heredity What is the difference between phenotype and genotype? What is the difference between homozygous and heterozygous?

Phenotypes and Genotypes Phenotype: Organism’s physical traits – Ex: brown eyes, blue eyes, straight hair, curly hair Genotype: Organism’s genetic makeup; allele combination – Ex: Ss, AA, bb

Homozygous and Heterozygous Homozygous: Two identical alleles for a trait – Ex: BB – homozygous dominant bb – homozygous recessive Heterozygous: Two different alleles for a trait – Ex: Bb, Ss, Aa, Tt

Phenotypes and Genotypes Guinea Pig Example: Black fur: B White fur: b Phenotype and Genotype Genotype: BB Phenotype: black fur Genotype: Bb Phenotype: black fur Genotype: bb Phenotype: white fur

Use a Punnett Square to find the probabilities of each genotype & phenotype Brown eyes = B Blue eyes = b Mother: BbFather: BB Genotype:BB _____ Bb _____ bb _____ Phenotype:Brown eyes _____ Blue eyes _____ Mother: BbFather: bb Mother: BbFather: Bb

Codominance Codominance: Alleles are neither dominant or recessive – Both alleles are expressed – Ex: feather color in chickens F B : black feathers F W : white feathers F B F W : black and white