Download Punnett Square Problems

Punnett Square Problems
Name _______________________
Period ___ Date ________
Monohybrid Problems
1. In rabbits the allele for black coat color (B) is dominant over the allele for brown coat
color (b). What is the genotypic ratio and phenotypic ratio for a cross between an
animal purebred for black coat color and one purebred for brown coat color? What is
the probability of having the next baby rabbit with a black coat?
1) Make a key:
Dominant: genotype? ____ phenotype? ________________________
Recessive: genotype? ____ phenotype? ________________________
2) Write Parent Genotypes:
Parent 1: genotype? ____ phenotype? ________________________
Is parent 1 purebred dominant, hybrid, or purebred recessive?
Parent 2: genotype? ____
phenotype? ________________________
Is parent 1 purebred dominant, hybrid, or purebred recessive?
3. Perform cross using square
_____ X _____
(parent 1) (parent 2)
4. Write Genotypes and Phenotypes and ratios
-
___________ : ____________
5) Be sure to answer any additional questions.
(Write the probabilities for the phenotypes in fractions and percent-form.)
General Rules to solving genetic crosses using Punnett Squares.
1. Make key
2. Write Parent Genotypes
3. Perform cross using square
4. Write Genotype and Phenotype ratios
5. Be sure to answer any additional questions.
Complete the following problems on your own lined
paper. Staple the finished product to this handout.
For each problem write out the key and answer each
step just like example #1.
General Rules to solving genetic crosses using Punnett Squares.
1. Make key
2. Write Parent Genotypes
3. Perform cross using square
4. Write Genotype and Phenotype ratios
5. Be sure to answer any additional questions.
2. White (W) hair in sheep is caused by the dominant gene while black (w) hair is
recessive. A hybrid white male and a black female are parents of a black lamb. What
are the genotypic and phenotypic ratios? What is the probability that their next lamb
will be white?
3. Albinism is recessive in humans. An albino man marries a woman who is not albino,
but had an albino father. What is the probability of this couple having a child that is
not an albino? What are the genotypic and phenotypic ratios?
4. In Teenage Mutant Ninja Turtles, green shells are dominant over brown shells.
Leonardo, who is bybrid for a green shell, marries the lovely Lisa, who has a brown
shell. What are the genotypic and phenotypic ratios? What is the probability they will
have a brown shelled offspring?
5. In humans, polydactyly (an extra finger on each hand or toe on each foot) is due to a
dominant gene. When one parent is polydactylous, but hybrid, and the other parent is
normal, what are the genotypic and phenotypic ratios of their children? What is the
probability they will have a child with normal fingers?