Genes Observable traits are the result of genes. – Genes are found on the chromosomes in our cells – Each observable trait is determined by two genes, one gene coming from each parent – A potential gene that a parent can pass to their offspring is called an allele

Alleles Alleles are expressed using letters – Capital letters represent a dominant allele – Lower case letters represent a recessive allele Each trait that we see is represented by two alleles, one randomly coming from each parent Example: we might write eye color as Bb

Allele Rules Dominant allele will always show over recessive allele, ex. BB, Bb, or bB would show the dominant trait Order does not matter The only way to see a recessive trait is to have a pair of recessive alleles, ex. bb Exact matching alleles are called homozygous or pure, ex. BB or bb Different allele pairs are called heterozygous or hybrid, ex. Bb

Genotype Phenotype The written form of an observable trait using letters, ex. BB, Bb, bB, bb The appearance of the offspring based on the allele pairs given to them by their parents, what we see, ex. Blue eyes

Punnett Squares A tool used to organize the different possible combinations of alleles parents can pass on to their offspring Each square of the Punnett Square represents a 25% chance the offspring will get a given pair of alleles