Practice Problems

Practice Problems

Now let’s try some of these Punnett squares!

1. An albino man and a normally pigmented woman who is heterozygous for the trait, have children. What is the probability that they will have an albino child?

2. Polydactyly is a condition where those affected have more than five fingers and/or toes. It is a dominant disorder. If a man without polydactyly marries a woman who is heterozygous for the condition, what is the proportion of their children that will have polydactlyly?

3. In chile pepper plants, an allele for an ultra hot taste (H) is dominant over the allele for more mild flavor (h). Give the genotypic and phenotypic ratios for the results of each of the following crosses:

(a) Hh X hh

(b) Hh X Hh

4. In human beings, the allele for brown eyes is dominant (B) over blue eyes (b). Suppose a blue-eyed man marries a brown-eyed woman whose father was blue-eyed. What proportion of their children would you predict will have blue eyes?

5. A brown-eyed man whose father was brown-eyed and whose mother was blue-eyed marries a blue-eyed woman whose father and mother were both brown-eyed. The couple has a blue-eyed son. For which of the individuals mentioned can you be sure of the genotypes? What are their genotypes? What genotypes are possible for the others?

6. In velociraptors, assume that 4- inch razor-sharp claws (R) are dominant over dull claws (r). Suppose a female velociraptor with 4- inch razor-sharp claws who is heterozygous mates with a dull-clawed male raptor who's mother and father had 4- inch razor-sharp claws. What proportion of the young would you predict will have 4- inch razor-sharp claws? What is your most precise estimate of the number of young from a 80 egg nest resulting from this mating that would have 4-inch razor-sharp claws? What would be the father’s parent’s genotypes?

7. A man is accused in a paternity suit of being the father of a child. He has type B blood, while the woman has type AB blood. The child's blood is tested and found to be type O. The medical technician who is conducting the test, checks and double checks the results, and announces to the court, that there is a major problem. Could the accused man potentially be the father of the baby? What's the problem that the med-tech has detected?

Practice Problems- dihybrid crosses

( Rember, foil to determine the possible gametes!)

8. In cats, white spots are caused by a dominant allele called W, while ww individuals are solid-colored. Also short hair(S) is dominant to long hair(s). What would the probability be of getting a white-spotted, long-haired cat from this cross: WWSs x Wwss? What are the phenotypes of the parents? (Rember, foil to determine the possible gametes!)

9. What type of plants (phenotypes) will be produced by two parent plants heterozygous for both seed color AND for seed shape? (Round is dominant over wrinkled and Yellow dominant over green)

10. Superman is homozygous dominant for super strength and heterozygous for x-ray vision (SSXx). He falls in love with Wonder Woman who is homozygous recessive for both traits. What is the probability that a child will inherit both super strength and x-ray vision?

11. In dogs, short hair is dominant over long; dark hair is dominant over light. One dog is heterozygous for hair length and shows the recessive trait for hair color. Another dog is homozygous dominant for hair length and heterozygous for hair color. Construct a Punnett square showing a cross between these two animals. Identify possible phenotypes

12. A tossed coin heads six times straight. What is the probability of it being tails on the 7th toss or for that matter any toss?

A. 100% B. 60% C. 50% D. 40%

13. Two coins are tossed together 40 times. Approximately how many times should both land tails?

A. 10 B. 20 C. 25 D. 30

14. Tay-Sachs disease is a fatal, recessive disorder. People born with this disorder generally die before they are five years old. A couple has had three children all of whom have died of Tay-Sachs disease. What is the probability that their fourth or any child will be healthy with regard to Tay-Sachs disease?

A. 1/256 B. 3/4 C. 1/4 D. 0

15. What is the probability that the above couple will have a fourth child who has Tay-Sachs disease?

A. 1/256 B. 3/4 C. 1/4 D. 0

16. What is the probability that the above couple would have three children all with Tay-Sachs disease?

A. 1/64 B. 3/4 C. 1/8 D. 1/4

17. A blood test can be performed on individuals to see if they are homozygous or heterozygous for Tay-Sachs disease. One member of a particular couple is homozygous and the other is heterozygous. What is the probability that this couple will have a child with Tay-Sachs disease?

A. 0% B. 25% C. 50% D. 100%

18. What is the probability that the couple’s children will be carriers (heterozygous)?

A. 0% B. 25% C. 50% D. 100%

19. What is the probability that this couple will have two children who are both carriers (heterozygous)?

A. 0% B. 25% C. 50% D. 100%

20. In fruit flies, gray body (G) is dominant over black body (g). Two gray flies were mated and produced 150 gray flies and 50 black flies. The parent were probably these genotypes:

A. GG and GG B. Gg and Gg C. GG and Gg D. Gg and gg

21. What will be the result if a Gg fruit fly mates with a gg fruit fly?

A. All offspring will show the dominant trait.

B. All offspring will show the recessive trait.