Name: ______________________________

Period: ______

Practicing Punnett Squares

Steps of solving Punnett square problems:

Step 1         Identify the ______________ you are working with

Step 2         Assign a letter for the trait:

        *dominant allele = ___________________ letter

        *recessive allele = _______________________ letter

Step 3        List the ____________________ of each parent

Step 4         Draw and solve the ______________________________

Step 5         List the possible ____________________________

        *list the different genotypes and the percent of each

        *list the different phenotypes and percent of each

Problem #1: 

In humans, the gene for an “inny” belly button is dominant to the gene for an “outie” belly button. Calculate

the possible genotypes and phenotypes for a cross between a homozygous dominant female with a

homozygous recessive male.

        Trait: ____________________________

        Parent Cross __________x__________

        Punnett Square

Possible Genotypes percentages ___________________

(what letter combinations are in the boxes.)

        Possible Phenotypes percentages ____________________

                 (What will the offspring look like because of their genotype.)

Problem #2

In geckos, the gene for long tails is dominant to the gene for shorter tails. Calculate the possible genotypes and phenotypes for a homozygous long tailed female and a male that is heterozygous for tail length. (Remember: heterozygous means one of each type of allele, so if you are using the letter “A,” the genotype would be “Aa”.)

        Trait: _____________________

        Parent Cross __________x__________ 

        Punnett Square

        Possible Genotypes percentages ________________________

        Possible Phenotypes percentages _______________________

Problem #3

In Hollywood mutant turtles, the gene for skin color green is dominant to that for orange skin. Calculate the possible genotypes and phenotypes for a hybrid female and a hybrid male.

        Trait: ______________________

        Parent Cross __________ x_________

        Punnett Square

Possible Genotypes percentages _______________________

            Possible Phenotypes percentages ______________________

Problem #4

In leopards, the gene for square spots is recessive to the gene for circular spots. Calculate the possible genotypes and phenotypes for a hybrid female and a pure circular male.

Trait: _______________________

Parent Cross ________x_____________

Punnett Square

Possible Genotypes percentages ________________________

                Possible Phenotypes percentages _______________________

Problem #5

In mice, long tails are dominant over short tails. Mickey and Minnie are both heterozygous for long tails. Calculate the possible genotypes and phenotypes of their children.

Trait: ______________________

        Parent Cross __________ x_________

        Punnett Square

Possible Genotypes percentages _______________________

           Possible Phenotypes percentages ______________________

Problem #6

In cats, stripes are dominant over no stripes. Mitten is heterozygous for stripes, while Sammy is homozygous for no stripes. Calculate the possible genotypes and phenotypes of their children.

Trait: ______________________

        Parent Cross __________ x_________

        Punnett Square

Possible Genotypes percentages _______________________

             Possible Phenotypes percentages ______________________

Problem #7

In dogs, having no patches is dominant over having patches. Spot the dog is homozygous for patches, while Snow the dog is heterozygous for patches. Calculate the possible genotypes and phenotypes of their children.

Trait: ______________________

        Parent Cross __________ x_________

        Punnett Square

Possible Genotypes percentages _______________________

             Possible Phenotypes percentages ______________________