Genetic crosses

• we have two copies from each gene, one from each parent. different versions of a gene are called alleles.
• in a genetic diagram, letters are used to represent alleles. Dominant alleles are always shown with a capital letter and recessive alleles with a lower case letter.
• if you're homozygous you have two of the same alleles. if you have AA you have both dominant alleles (homozygous dominant). if you are aa you have both recessive alleles (homozygous recessive.)
• if you're heterozygous you have two different alleles. If you have Aa you have one dominant and one recessive allele (heterozygous)
• if you are heterozygous you have two different alleles
• phenotypic ratio = number of individuals showing particular phenotype / total number of individuals