Warm-up Turn in your meiosis simulation activity and your punnett piggy activity sheets

Dihybrid crosses Dihybrid crosses are punnett squares used to predict the probability of an offspring having 2 traits at the same time. Ex: What are the chances of my baby having brown eyes AND blond hair.

Dihybrid crosses Yellow seeds (Y) are dominant to green seeds (y) Round seeds (R) are dominant to wrinkled seeds (r) If both parents are heterozygous for both traits, what are the genotypic and phenotypic ratios of the offspring?

Step 1 Draw a box and divide it into 16 squares.

Step 2 Determine the genotypes of the parents YyRr x YyRr Ex: cross two pea plants that are heterozygous for yellow peas and round peas. Yellow is dominant to green and round is dominant to wrinkled.

Step 3 Determine all of the possible gamete combinations for each parent by using the F.O.I.L. method FOIL= first, outside, inside last Ex: YyRr First- YR Outside- Yr Inside- yR Last- yr Principle of independent Assortment!

Step 4 Write all of the possible combinations of alleles on the sides and top of the punnett square. YR Yr yR yr YR Yr yR yr

Step 5 Do the cross Remember to keep all of one letter together and all of the 2 nd letter together. YR Yr yR yr YYRR YYRr YYrr YyRR YyRrYyrr YyRr YyRR YyRr yyRR yyRr yyrr yyRr Yyrr YyRr

Step 6 Go through the results and determine what the phenotype of each offspring would be YR Yr yR yr YYRR Yellow round YYRr Yellow, round YYRr Yellow, round YYrr Yellow,w rinkled YyRR Yellow, round YyRr Yellow, round Yyrr Yellow, wrinkled YyRr Yellow, round YyRR Yellow, round YyRr Yellow, round yyRR Green, round yyRr Green, round Yyrr Green, wrinkled yyRr Green, round Yyrr Yellow, wrinkled YyRr Yellow, round yR

Step 7 Figure out the phenotypic ratio or answer whatever question they ask you. 9:3:3:1 Example: what are the chances of having a yellow and wrinkled pea? 3/16 YR Yr yR yr YYRR Yellow round YYRr Yellow, round YYRr Yellow, round YYrr Yellow, wrinkled YyRR Yellow, round YyRr Yellow, round Yyrr Yellow, wrinkled YyRr Yellow, round YyRR Yellow, round YyRr Yellow, round yyRR Green, round yyRr Green, round Yyrr Green, wrinkled yyRr Green, round Yyrr Yellow, wrinkled YyRr Yellow, round yR

Incomplete Dominance Heterozygous offspring show a phenotype that is in between the phenotypes of the two homozygous parents

Incomplete Dominance RR W W RWRWRWRW RWRWRWRW Crossing homozygous parents to produce F 1 generation THE ALLELES REMAIN DISTINCT; ONLY THE PHENOTYPE APPEARS BLENDED.

Codominance Both alleles in the heterozygote express themselves fully. Example: Blood types Roan cattle

Codominance A person homozygous for Type A blood And a person homozygous for Type B blood Will produce a child that will demonstrate both Type A and Type B blood (Type AB)

Summary Incomplete Dominance Traits are blended (red + white = pink) Codominance Both traits are expressed (A + B = AB)

Multiple Alleles A gene that has more than two possible alleles, though only two alleles are present at a time. EX: Blood Type A, B, O

Polygenic Traits Polygenic Traits- Traits controlled by two or more genes that interact. Ex: Human Eye Color and skin pigment

Multiple Alleles More than two possible alleles, but only two present at a time. Polygenic Trait Single trait controlled by more than one gene. In summary: