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Dihybrid Crosses. Why Dihybrid ?. Sometimes there are traits in the genotype that are linked The traits that have two genes require a special punnett square. Why Dihybrid?. When there are two genes we use a dihybrid cross
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Why Dihybrid? • Sometimes there are traits in the genotype that are linked • The traits that have two genes require a special punnett square
Why Dihybrid? • When there are two genes we use a dihybrid cross • A dihybrid cross is a special type of punnett square that lists all the genotypes from two linked genes
How To Set It Up • In order to set up the dihybrid cross we need to figure out all of the possible genotypes • Remember there are two genes • We can have a dominant or recessive for each gene in the linked genes
How To Set It Up • The hardest part of setting up your Dihybrid is setting up the alleles • Each parent is giving a pair of linked genes • That means they will be giving one (A or a) and one (B or b) • We need to account for all of the possibilities for gene (A or a) and gene (B or b) AABB x aabb
How To Set It Up AaBb • Once you have all of the genotypes, you would list the father and the mother • In order to make it easy, think about solving a “FOIL” method problem AaBb
Solving the Cross • Now all we do is solve • Each box should have a column and a row • Each square should have two different alleles for each genotype
Practice • AABB homozygous gene is crossed with aabb homozygous recessive • What are the genetic outcomes
Practice • AaBb heterozygous gene is crossed with a aabb homozygous recessive gene • What are the possible genetic outcomes