Punnett Squares

•A Punnett Square is a tool used to predict what genes an offspring will have based on the genes of the parents.

Punnett Square Cartoon

New Vocabulary!!!

•Purebred – a genotype that has the same two alleles (RR or rr)

•Hybrid – a genotype that has 2 different alleles (Rr)

t

t

TT

One parent’s genotype

The other parent’s genotype

T

T

T

T

t t

t t

ALL the offspring will be Tt (hybrid)

r

R

RR

Dominant – Round SeedsRecessive – Wrinkled Seeds

Offspring’s Genotype:

RR = ________%

Rr = ________%

rr = ________%

Offspring’s Phenotype:

Round = _______%

Wrinkled = _______%

r

R

rr

Dominant – Round SeedsRecessive – Wrinkled Seeds

Offspring’s Genotype:

RR = ________%

Rr = ________%

rr = ________%

Offspring’s Phenotype:

Round = _______%

Wrinkled = _______%

r

R

rR

Dominant – Round SeedsRecessive – Wrinkled Seeds

Offspring’s Genotype:

RR = ________%

Rr = ________%

rr = ________%

Offspring’s Phenotype:

Round = _______%

Wrinkled = _______%

You have one parent that is RR and another parent that is Rr. What is the probability they will have an offspring with a recessive phenotype?

SpongeBob SquarePants recently met SpongeSusie Roundpants at a dance. SpongeBob is hybrid for his square shape, but SpongeSusie is round. Create a Punnett square to show the possibilities that would result if SpongeBob and SpongeSusie had children.

Mickey Mouse is purebred for his large ears while Minnie Mouse has small ears. If Mickey and Minnie have children, what is the probability that their children will have big ears?

The presence of freckles is a dominant trait . The absence of freckles is a recessive trait. A child is born and has NO freckles. The mother has freckles and the father does not have freckles. What is the genotype of the mother? Use the letter “F”.

While eating at the Krusty Krab Patrick met a cut star called Patty. Two years later Patrick and Patti were married. Patrick is purebred for his pink color, while Patty is hybrid for her yellow color. If Patrick and Patty decide to have little stars what is the probability that the offspring will be pink like Patrick?

Mr. Krabs and his wife recently has a Lil’Krabby, but is has not been a happy occasion for them. Mrs. Krabs has been upset

since she first saw her new baby who had short eyeballs. She claims that the hospital goofed and mixed up her baby with

someone else’s baby. Mr. Krabs is purebred for his tall eyeballs, while his wife is hybrid for her tall eyeballs. Some

members of her family have short eyes, which is the recessive trait. Did the hospital make a mistake?

SpongeBob’s aunt is famous around town for her itty, bitty stubby nose! She recently met a cute squarepants fellow who also has a stubby nose, which is a recessive trait. Would it be possible for them to have a child with a regular long nose? Why or why not? Create a Punnett square to help you answer this question.

If SpongeBob’s aunt from the last question wanted children with long noses, what type of fellow would she need to marry in order to give her the best chances? Create a Punnett square to help you answer this question.