1. The length of the index fingers inherited. Short is dominant in males and recessive in females. Show the types of offspring that could be expected if a heterozygous short index fingered male marries a long index fingered female.
2. A certain species of frog has the XY method of sex determination. When raised at about 70° F, they produce approximately half males and half females, as would be expected. However, when the tadpoles are kept in water which is about 90° F, they produce all males. From your study, what theory would you propose to account for this?
3. Show the type of offspring which would be expected from a cross between a heterozygous normal feathered cock to a hen, homozygous for cock-feathering.
4. In pheasants, the male has brightly colored plumage (feathers), while the female is drab. This is inherited as a dominant, sex-linked characteristic. Cross a heterozygous brightly colored male with a female homozygous for colored feathers. Give the phenotypic ratios for both male and females.
5. Assume that you are a consulting psychologist. A woman comes to you with a problem. Her mother has pattern baldness, but her father has a normal head of hair. Her older brother is rapidly losing his hair and will soon be bald. The woman is a circus acrobat who hangs by her hair as a part of her act. She wants to know if she might also become bald so that she can change her profession before it becomes too late, if that should be necessary. Using a Punnett square, show her the possibilities.
6. A man has one inch hair on the ears, a condition which appears to be due to an allele on the non-homologous portion of the Y-chromosome. He marries a normal woman. Show the types of children which they might expect to have.
7. If you have type B blood and you marry a person with type AB blood, what blood types might your children have?
8. Suppose two newborn babies were accidentally mixed up in the hospital (something that rarely happens). In an effort to determine the parents of each baby, the blood types of the babies and the parents were determined.
Baby 1: Type O Mrs. Smith: Type B Mrs. Brown: Type B
Baby 2: Type A Mr. Smith: Type B Mr. Brown: Type AB
Show with Punnett squares which baby belongs to which parents and the genotype of each person.
9. Can the parent-child identification always be determined by blood types? _____________ Give a hypothetical situation to support your answer.
10. A woman sues a man for the support of her child. She has type A blood, the child has type O, and the man has type B. Could the man be the father? ____________ Prove your answer with a Punnett square.
11. Further testing of the subjects in problem #10 shows that both the man and the woman are Rh negative while the child is Rh positive. Would this information be of any value in the case? ___________________ Explain.
12. A wealthy elderly couple dies together in an accident. Soon a man shows up to claim their fortune, contending that he is their only son, who ran away at an early age. Other relatives dispute this case. Hospital records show that the deceased couple were of blood types AB and O, respectively. The claimant to the fortune is type O. Do you think the claimant was an impostor? __________ Use Punnett squares and explain.
13. Give a hypothesis as to how large groves of navel (seedless) oranges have come into existence.
14. Using your knowledge of non-disjunction, describe how you would explain the appearance of a male calico cat in a litter.
15 A geneticist working with guinea pigs crossed black animals with albino animals twice, using different animals. In the first cross, she obtained12 black progeny, but in the second cross, she obtained 6 black and 5 albino progeny. Assuming that coat coloration is determined by a single gene with possible alleles B and b, what are the likely genotypes of the parents in each cross?
16. Mendel discovered that axial position (in the angle of stem and leaf) of pea flowers is dominant over terminal position (end of stem). Using A for axial and a for terminal, determine the kinds of proportions of gametes and progeny produced by each of the following crosses: AA x aa, AA x Aa, Aa x aa, Aa x Aa.
17. In sesame, the one-pod condition (P) is dominant over the three-pod condition (p), and normal leaf (L) is dominant over wrinkled leaf (l). The two characters are inherited independently. Determine the genotypes and phenotypes of the two parents that product the following progeny: 318 one-pod normal; 98 one-pod wrinkled; 323 three-pod normal; 104 three-pod normal.
18. Phenylketonuria (PKU) is an inherited disease caused by a particular recessive allele. If a woman is heterozygous and her husband is homozygous normal for the trait, and if the couple plans to have four children, how many children would you expect to have PKU?
19. A monohybrid testcross ?? x aa gives all dominant phenotypes. What was the unknown genotype?
20. How many different kinds of gametes can an organism RrSS produce?
21. Steve and Karen are planning to get married and decide to do a family pedigree for eye color in their genetics class. Blue eyes are recessive to brown eyes. Steve has brown eyes, like his three brothers. His mother and grandmother have blue eyes, but his father and all other grandparents have brown eyes. Brown-eyed Karen has one blue-eyed sister and one brown-eyed sister and a mother with blue eyes. Her father and all her grandparents have brown eyes. Construct a three-generation family pedigree for eye color, showing phenotype and most likely genotype for each person.
22. Steve and Karen were married and had two brown-eyed children. What is the probability that their third child will have blue eyes?
23. Among Hereford cattle there is a dominant allele called polled; the individuals that have this allele lack horns. You have acquired a herd consisting entirely of polled cattle, and you carefully determine that no cow in the herd has horns. Among the calves born that year, however, some grow horns. You remove them from the herd and make certain that no horned adult has gotten into your pasture. Despite your efforts, more horned calves are born the next year. What is the reason for the appearance of the horned calves? If your goal is to maintain a herd consisting entirely of polled cattle, what should you do?
24. An inherited trait among humans in Norway causes affected individuals to have very wavy hair, not unlike that of a sheep. The trait, which is called woolly, is very evident when it occurs in families; no child possesses wooly hair unless at least one parent does. Imagine you are a Norwegian judge, and that you have before you a woolly-haired man suing his normal-haired wife for divorce because their first child has woolly hair but their second child has normal hair. The husband claims this constitutes evidence of infidelity on the part of his wife. Do you accept his claim? Justify your decision.
25. If two normally pigmented persons heterozygous for albinism marry, what proportion of their children would be expected to be albino?
26. You inherit a racehorse and decide to put him out to stud. In looking over the studbook, however, you discover that the horse's grandfather exhibited a rare clinical disorder that leads to brittle bones. The disorder is hereditary and results from homozygosity for a recessive allele. If your horse is heterozygous for the allele, it will not be possible to use him for study, since the genetic defect may be passed on. How would you go about determining whether your horse carries this allele?
27. In the fly Drosophila, the allele for dumpy wings (d) is recessive to the normal long-wing allele (D), and the allele for white eye (w) is recessive to the normal red-eye allele (W). In a cross of DDWw x Ddww, what proportion of the offspring are expected to be "normal" (long wings, red eyes)? What proportion are expected to have dumpy wings and white eyes?
28. In some families, children are born with recessive traits (and, therefore, must be homozygous for the recessive allele specifying the trait), even though one or both of the parents do not exhibit the trait. What can account for this?
29. You collect two individuals of Drosophila, one a young male and the other a young, unmated female. Both are normal in appearance, with the red eyes typical of Drosophila. You keep the two flies in the same bottle, where they mate. Two weeks later, the offspring they have produced all have red eyes. From among the offspring, you select 100 individuals, some male and some female. You cross each individually with a fly you know to be homozygous for the recessive allele "sepia," which leads to black eyes when homozygous. Examining the results of your 100 crosses, you observe that in about half of the crosses only red-eyed flies are produced. In the other half of the crosses, however, the progeny of each cross consists of about 50% black-eyed flies. What must have been the genotypes of your original two flies?
30. In one experiment, Mendel crossed a true-breeding pea plant having green pods with a true-breeding pea plant having yellow pods. All of the F1 plants had green pods.
a. Which trait (green or yellow pods) is recessive? Can you explain how you arrived at your conclusions?
b. Suppose the F1 plants are self-pollinated and 135 F2 plants are produced. What phenotypes should be present in the F2 generation, and how many of the plants in that generation should show each of those phenotypes?
31. Being able to curl the sides of the tongue in a U-shape is under the control of dominant allele at one gene locus. When there is a recessive allele at this locus, the tongue cannot be rolled. Having free ear lobes is a trait controlled by a dominant allele at a different gene locus. When there is a recessive allele at this locus, earlobes are attached at the jawline. The two genes controlling tongue rolling and free earlobes assort independently. Suppose a woman who has free earlobes and who can roll her tongue marries someone who has attached earlobes and who cannot roll his tongue . Their first child has attached earlobes and cannot roll the tongue.
a. What are the genotypes of the mother, the father, and the child?
b. If this same couple has a second child, what is the probability that it will have free earlobes and be unable to roll the tongue?
32. A man is homozygous dominant for ten different genes. How many genotypically different types of sperm could he produce? A woman is homozygous recessive for eight of these ten genes, and she is heterozygous for the other two. How many genotypically different types of eggs could she produce? What can you conclude regarding the relationship between the number of different gametes possible and the number of heterozygous and homozygous genes that are present?
33. Mendel crossed a true-breeding, tall, purple-flowered pea plant with a true-breeding dwarf, white-flowered plant. All the F1 plants were tall and purple-flowered. If an F1 plants now self-pollinated, what is the probability of obtaining an F2 plant heterozygous for the genes controlling height and flower color?
34. Assume that a new gene recently was identified in mice. One allele at this gene locus produces a yellow fur color. A second allele produces a brown fur color. Suppose you are asked to determine the dominance relationship between these two alleles. (Is it simple dominance, incomplete dominance, or codominance?) What types of crosses would you make to find the answer? On what types of observations would you base your conclusions?
35. If a man homozygous for widow's peak (dominant) marries a woman homozygous for continuous hairline (recessive), what are the chances the children will have widow's peak? Will have a continuous hairline?
36. In a fruit fly experiment, two gray-bodied fruit flies produce mostly gray-bodied offspring but some offspring have black bodies. If there are 280 offspring, how many do you predict will have gray bodies and how many will have black bodies? How many of the 280 offspring do you predict will be heterozygous? If you wanted to test whether a particular gray-bodied fly was homozygous dominant or heterozygous, what cross would you do?
37. In humans, the allele short fingers is dominant over that for long fingers. If a person with short fingers who had one parent with long fingers marries a person with long fingers, what are the chances for each child to have short fingers?
38. John has unattached earlobes like his father, but his mother has attached earlobes. What is John's genotype?
39. In rabbits, black color is due to a dominant allele B and brown color to its recessive allele b. Short hair is due to the dominant allele S and long hair is due to recessive allele s. In a cross between a homozygous black, long-haired rabbit and a brown, homozygous short-haired one, what would the F1 generation look like? The F2 generation? If one of the F1 rabbits reproduced with a brown, long-haired rabbit, what phenotypes, and in what ratio, would you expect?
40. In horses, black coat B is dominant to brown coat b, and being a trotter T is dominant to being a pacer t. A black horse who is a pacer is crossed with a brown horse who is a trotter. The offspring is a brown pacer. Give the genotypes of all these horses.
41. The complete genotype of a gray-bodied fruit fly is unknown. When this fly is crossed with a black-bodied, short-winged fruit fly, the offspring all have a gray body but about half of them have short wings. What is the genotype of the gray-bodied, long-winged fly?
42. In humans, widow's peak (pointed) hairline is dominant to continuous (smooth) hairline, and short fingers is dominant to long fingers. If an individual who is heterozygous for both traits is married to an individual who is recessive for both traits, what are the chances that a child will also be recessive for both traits?
43. A man of blood group A marries a woman of blood group B, and they have a child of blood group O. What are the genotypes of these three people? What other genotypes, and in what frequencies, would you expect among the children of such a marriage?
44. The daughter of a man with hemophilia (a sex-linked condition) marries a man who is normal. If the couple has four daughters and four sons, how many of each se would you expect to be born with hemophilia?