Download Inheritance of Two Trait

Name:_______________________________________________________
Mendel’s Law of Independent Assortment: Inheritance of Two Traits Simultaneously
1. After a much talked about romance at Monsters Inc., Mike and Celia were married and are
now expecting a little monster of their own! Green skin is dominant to purple and having
snakes for hair is dominant to having horns. Mike is heterozygous for green skin and has horns. Celia
is heterozygous for snakes and has purple skin.
•
•
What are the genotypes for Mike and Celia?
Construct a Punnett Square to show the possible
genotypes of their children
• What are the chances of having a monster with green
skin and snakes for hair?
2. In guinea pigs, black coat is dominant to white and a rough coat is dominant to a smooth one. A pure bred
black, pure smooth guinea pig is mated with a pure bred white, pure rough one. Then two members of that
first generation were bred with each other.
What is the genotype and phenotype ratio of the first generation?
What would be the phenotype ratio of the second generation?
Parents Genotypes: __ __ __ __ X __ __ __ __
First generation genotype: __ __ __ __
Genotype of second parents: __ __ __ __ X __ __ __ __
Gametes produced by the second parents:
3. In fruit flies, red eyes are dominant to magenta eyes.
Long wings are dominant to short wings. A heterozygous,
red-eyed, short winged male is bred with a magenta – eyed,
heterozygous long winged female. What percentage of their
offspring would you expect to have magenta eyes and short wings?
Bull: __ __ __ __
H1: __ __ __ __
H2: __ __ __ __
H3: __ __ __ __
H4: __ __ __ __
Answer: ___________________
Calf 1: __ __ __ __
Calf 2: __ __ __ __
Calf 3: __ __ __ __
Calf 4: __ __ __ __
4. In cattle, black coat is dominant
to red coat. Hornless cows are dominant
to horned ones. A bull was mated with
four heifers. H1 was black/hornless, and
gave birth to a horned /black calf. H2 was
hornless /red, and gave birth to a horned/
black calf. H3 was horned / black, and
gave birth to a horned /red calf. H4
?
was horned /red, and gave birth to a
hornless / black calf. What is the
genotype of the bull? What are the
genotypes of the four heifers?
Their calves?
….More practice problems… (Good candidates for a test! Hint, hint, wink wink)
Suppose that you experiment with a certain species of insect and discover that most of the individuals
bodies are dark brown but a few are tan. The original parents (P1) are dark brown and tan. All of the
offspring from the first generation (F1) are dark brown. When these F1 offspring are mated to each
other, you get the following F2 generation: 338 dark brown, and 112 tan.
Don’t worry about
it, you will get some
I want tan
of both!
I want brown
babies!
babies!
5. What is the dominant form of this trait?
6. What is the recessive form of this trait?
7. What is the genotype of the P1 parents?
8. What is the genotype ratio of the F2 offspring?
9. What is the phenotype ratio of the F2 offspring?
In foxes, red coat color is dominant to gray coat color. Having long tails are dominant to having short
tails. For the following problem use the letter R and r for the coat color trait, and the letter L and l for
the tail length trait.
Use the following information to answer questions 10-13.
A red coat, long tailed fox is mated with a gray coat, short tailed fox. The offspring that come from
this pair over a number of years are red coated, long tailed foxes and red coated, short tailed foxes.
10. What are most probable genotypes of the parents?
11. What is the genotype of the red coat, long tailed offspring?
12. What is the genotype of the red coat, short tail offspring?
13. Go back and look at what you answered for 10. Is there any situation you can think of that might
cause you to change your answer? Explain.
Name: ____________________________________________________
If you can do the following, you will never forget how to do a genetics problem…EVER!
Using Punnett squares are useful to predict the results of dominant and/or recessive genes expressing
themselves in the next generation. In nature however, an individual’s phenotype results from the interaction
of thousands of genes and many chromosomes, in ways we are only beginning to understand. We have done
problems showing how one and two traits at a time are considered. Now complete the following example with
three traits, showing how quickly the number of squares needed to show all variations can grow.
In fruit flies, the following genes are located on separate chromosomes:
Gene
1
2
3
Dominant allele
Having eyes (E)
Hairy body (H)
Large wings (L)
Recessive allele
Eyeless (e)
Hairless body (h)
Small wings (l)
Predict the results of a cross between two fruit flies that are heterozygous for
all traits involved.
Parental Genotypes : __ __ __ __ __ __ X __ __ __ __ __ __
Predict the phenotype ratio of the offspring:
_____ Eyes, Hairy, Large
_____ Eyes, Hairy, Small _____ Eyes, Hairless, Large _____ Eyes, Hairless, Small
_____ Eyeless, Hairless, Small ____ Eyeless, Hairless, Large ____ Eyeless, Hairy, Large ____Eyeless,Hairy,Small