Or what happens when you look at 2 traits at the same time Dihybrid crosses Or what happens when you look at 2 traits at the same time

Patterns of inheritance Monohybrid crosses. Looks at one (1) trait with 2 phenotypes Simple dominance characteristic phenotypic ratio 3:1 Test cross crosses unknown dominant phenotype with the homozygous recessive. If F1 has a 1:1 dominant to recessive ratio, then parent is heterozygous If the F1 is 100% dominant, then the parent was homozygous. Codominance both traits are expressed equally in the F1 heterozygote. RR = red WW = white RW = red and white stripes characteristic phenotypic ration 1:2:1 with 3 phenotypes Incomplete dominance the traits are blended in the F1 heterozygote. RR = red WW= White RW = pink

Dihybrid crosses crossing two (2) traits with 2 phenotypes each at the same time Kristina and Jessica decided to breed peas like Mendel for next years science fair. In their flowers single flower was Dominant (F) and double flower was recessive (f) . In the height trait tall is dominant(H) and short is recessive (h). The Genotype always has 4 letter 2 of each phenotypes What is the genotype of a parent that is heterozygous for both traits? Ff Hh What is the genotype of a parent that is homozygous dominant for height and heterozygous for flowers? Ff HH What is the genotype of the parents if they were pure for both recessive traits? ff hh

How do you make the gametes? This is the tricky part. Each parent has 2 of each trait. Each gamete has one of each trait. Parent Heterozygous for both traits Ff Hh There are 4 possible gametes. FH Fh fH fh Parent homozygous for 1 trait and heterozygous for the other. FF Hh There are only two different gametes. FH FH Fh Fh

This is Mendel’s Law of Independent Assortment If you cross two traits at the same time they assort themselves independently The inheritance of one trait has no effect on the inheritance of the other trait. Just because it’s tall doesn’t determine if it’s double or single.

What is the phenotypic ratio when we cross 2 peas that are heterozygous for each trait. Given: FfHh x FfHh Punnett square: because you have 4 possible gametes your Punnett has to be 4 x 4. Gametes FH Fh fH fh FH Fh fH fh

How do you find the phenotypic ratio? Gametes FH Fh fH fh FH Fh FFHh FFhh Ff Hh Ffhh fH FfHH FfHh ffHH ffHh fh FfHh Ffhh ffHh ffhh There are 4 Phenotypes single tall single short double tall double short The phenotypic ratio is 9 : 3 : 3 : 1 FfHh FFHH FFHh FfHH

You try this one. A pea homozygous dominant for height and heterozygous for flowers is crossed with a pea that is heterozygous for height and homozygous recessive for flowers Parents cross Ff HH x ffHh Possible gametes FH fH fH fh Punnett square Because each parent has only two gametes then the Punnett only has to have 4 squares

What is the phenotypic ratio of the F1 Gametes F1 Phenotypic ratio of F1 is : Single tall : double tall 2 : 2 FH fH fH ffHH FfHH fh FfHh ffHh