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Punnett Squares

Please answer these following questions on the blank  worksheets provided in this week’s class.

Question #1:

In pea plants, yellow peas are dominant over green peas.

Use a Punnett square to predict the genetic outcome (offspring) of a cross between two plants for yellow peas that yield a small amount of green peas.

Question #2:

The long hair of persian cats is recessive to the short hair of siamese cats. Complete a Punnett Square when a a purebred persian is mated with a purebred siamese cat.

Question #3:

The black coat of persian cat is dominant to the brown and tan coat of siamese. Complete a Punnett Square when a a purebred black persian is mated with a purebred brown siamese cat.

Question #4:

In four o’clock flowers, red plants are purebred for the dominant allele (R) of the gene for flower color. Plants with white flowers are purebred for the recessive (r) allele of the same gene. Plants with pink flowers have one of each of the two alleles. Complete a Punnett square that is expected when plants with pink flowers are intercrossed.

Question #5:

In humans, brown eyes (B) are dominant over blue (b). A brown-eyed man marries a blue-eyed woman and they have three children, two of whom are brown-eyed and one of whom is blue-eyed. Draw the Punnett square that illustrates this marriage.

Suppose one of the brown-eyed children marries someone with blue eyes. Use the second Punnett square to predict their offspring.


Here are some good Punnett practice problem sites. In fact, the problems above (and likely the questions on the midterm) come from these sites.

The Association for Biology Laboratory Education has a really good .pdf handout on the step by step procedure to solving Punnett square problems.Here is my own list:

If you’re daring, try the challenging Berkeley University problems (the answers are here)

The Concord Consortium has some cool apps — but you have to create an account to access…