Question

Simple Dominance with 2 genes

4. A gene in cats causes them to be black (dominant) or brown (recessive). A second gene causes cats to be agouti (have stripes on their hairs) or non-agouti (solid colored hairs).
   1. If you did a dihybrid cross between two black haired agouti cats, what fraction of the offspring would be expected to have each phenotype?

2. If a dihybrid black agouti cat mated with a brown cat that was heterozygous for the agouti gene, what fraction of the offspring would be expected to have each phenotype?

Test Cross

5. In mythical dragons, the ability to breath fire (F) is dominant over not being able to breathe fire (f). If you have a fire-breathing dragon and want to know whether it is homozygous or heterozygous, what could you do to find out? Explain how you would do the experiment.

6. In moths, having a long proboscis is dominant over having a short proboscis. You’re trying to figure out whether a particular female moth with a long proboscis is pure or a hybrid, so you cross it with a male moth that has a short proboscis. Half the offspring have long and half have short proboscii. What was the genotype of their mother?

7. In cats, black fur is dominant over brown fur. You have a black cat and you want to know whether it is true breeding for its black fur color, so you mate it with a brown cat. All 10 of their kittens are white. What was the genotype of your parent black cat? Can you be absolutely sure?

Incomplete Dominance

8. In rabbits, alleles for short fur (S) and long fur (L) are incompletely dominant. Hybrids have medium length fur. If you did a monohybrid cross with these rabbits, what ratio of short fur: medium fur: long fur would you see in the offspring?
9. In Andalusian fowl (similar to chickens), if you mate a true breeding white fowl with a true breeding black fowl, all the offspring will be blue. If you were to mate a blue fowl with a white fowl, what fraction of the offspring would be blue?

10. In cats, a particular gene determines whether the cat has white patches on top of its other color(s). Homozygous dominant cats are more than half white. Hybrid cats are less than half white, and homozygous recessive cats have no white patches at all. If a cat with white only on its feet mated with a cat that had no white at all, what fraction of the kittens would have each genotype and phenotype?

Codominance

11. In some horses, hair color is determined by one gene with two alleles. Homozygotes may be either red or white, and heterozygotes are roan (a mixture of red and white hairs). If you crossed two roan horses together, what fraction of the offspring would be roan?

12. Human blood type alleles are codominant. Lucy has type A blood. Her daughter Jenna has type O blood. Jenna’s father Ralph has never had his blood type tested.

1. 1. What is Lucy’s genotype?
2. 2. What are the possible genotypes that Ralph could have?

13. A woman with type 0 blood gives birth to a baby with type 0 blood. In a court case she claims that a man with type A blood is the father of the child. Could he be the father? Show why he can or cannot. Can it be proven on this evidence alone that he is the father?

Sex-linked genes

14. Hemophilia is a rare genetic disorder that results from a deficiency in blood clotting factors. When a person without hemophilia gets a cut, the bleeding lasts for a short time and then the blood clots to form a scab. People with hemophilia have only 1-5% of the blood clotting factors that other people have. Thus, when a hemophiliac gets a cut, it may continue to bleed for days or weeks, sometimes causing dangerous amounts of blood loss.  Hemophiliacs have to do special exercises to prevent their muscles from tearing and producing internal bleeding, and they can take supplemental blood clotting factors, but hemophilia has no known cure. Hemophilia is caused by a recessive allele that is located on the X chromosome.

If X^H is the allele for normal blood clotting, and X^h is the allele for hemophilia, draw a cross between a normal father and a mother who is a carrier for hemophilia. Then list the percentages of offspring that would get each genotype and phenotype.

15. Colorblindness is a sex-linked recessive trait. If a woman who was a carrier married a man who was colorblind, what percentage of their children (males and females) would be colorblind?

16. For a male to be colorblind, does he have to get the colorblindness allele from his mother, from his father, or both? For a female to be colorblind, does she have to get the colorblindness allele from his mother, from his father, or both?

Answer 1

Sorry, I can't answer more than one question due to answering guidelines. You have to post the questions seperately.