Download Genetics Station Work

Punnett Square Story Problems
1.
Use the letter A for genotypes for this one. Yellow is the dominant trait. Parent “A” pea plant has green seed color (recessive
allele).
a. What is the genotype of parent “A”?
b.
If this plant (Parent “A”) is crossed with a second plant (Parent “B”) to give 50% offspring plants with yellow seed
color (dominant allele) and 50% green, what are the possible genotypes for the parent “B”? What is the phenotype of
the parent “B”? (Hint: Use a Punnett Square and work backwards.)
2.
Is the disorder (recessive trait) that this pedigree chart is showing sex-linked? Explain your answer using words and Punnett
Squares.
3.
This question is about incomplete dominance (neither allele is fully dominant so they blend or average if they are both present).
a. If the gene for tail length in rats is incompletely dominant what length tail would a rat have who had a heterozygous
genotype?
b.
Draw a Punnett square for this heterozygous rat crossed with a long tail rat.
- What percentage probability for long tails?
- Short tails?
- Medium length tails?
c.
Now draw a Punnett square for a long tail rat crossed with a short tail rat.
- What percentage probability for long tails?
- Short tails?
- Medium length tails?
4.
Joshua and Bella want to understand the probability that they will have a child who has Cystic Fibrosis. Draw a pedigree chart
for their Case to help you explain and understand with them.
- Joshua and Bella have a son named Ian. Ian has been diagnosed with cystic fibrosis
- Joshua and Bella are both healthy
- Bella’s parents are both healthy
- Joshua’s parents are both healthy
- Joshua’s sister, Sara, has cystic fibrosis
Draw the pedigree chart, and write the genotype below each person to help explain.
5.
For this question assume that dog fur color depends on just two alleles of one gene.
a. Two black dogs have a white puppy. How might this be possible?
b.
6.
Looking at your explanation from part “a” could two white dogs then have a black puppy? Explain.
Use page 149 in the science book to help answer this problem. Draw a Punnett square for the following: The mom (Lucy) is
purebred dominant for normal vision. Lucy is married to Joe who is colorblind.
a. What is the percentage probability of girl offspring that could be colorblind? What percentage probability boy offspring
could be colorblind? If any girls are not colorblind will they be carriers? WHY?
b.
What does this mean for the sons of the GIRLS from above? (% phenotypes?)
7.
You are a genetic counselor, and a couple comes to you to get some advice. Bill and Judy look perfectly normal to you; however
they each have a mom who has green hair. (We will say this is a genetic trait, and green hair is the recessive allele.) The couple
has talked with their family and found that the green hair has never occurred in either of their father’s family lines. What are the
chances that each of these people is carrying the gene? What are the chances that they will have a child with green hair?
8.
This problem is about blood type. Remember Blood Type is codominant and has multiple alleles. Draw a Punnett square for one
parent type A and the other parent blood type B (they are both heterozygous).
a. What percentage probability for kids with type A blood? What percentage probability for type B blood? What
percentage probability for type O blood? What percentage probability for type AB blood?
**Number 9 and 10 are optional. (Supplemental questions for superstars [isn’t that you?])
9.
Use a Punnett square and work backwards to find the answer to this one if you have to. One parent (mom) has blood type of O.
The other parent (dad) does not know his blood type. They have three kids with type A blood and one kid with type B blood?
What type of blood does dad have? Explain how you know. (HINT: remember Punnett squares predict probability not exact
number of kids.)
10. You cross a goblin with blue hair with a goblin with red hair and you end up with goblins that have both blue and red hair at the
same time.
a. Explain how this is possible?
b.
Take two of these goblins that have both blue and red hair and cross them. Show the Punnett square and tell the percent
probability of the different phenotypes.