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- 1. Open EndedIn crossing a homozygous recessive with a heterozygote, what is the chance of getting an offspring with the homozygous recessive phenotype? A) 25% B) 100% C) 75% D) 50% E) 0%
- 2. Open EndedIn cattle, roan coat color (mixed red and white hairs) occurs in the heterozygous (Rr) offspring of red (RR) and white (rr) homozygotes. When two roan cattle are crossed, the phenotypes of the progeny are found to be in the ratio of 1 red:2 roan:1 white. Which of the following crosses could produce the highest percentage of roan cattle? A) roan x roan B) white x roan C) red x roan D) red x white E) All of the above crosses would give the same percentage of roan
- 3. Open EndedAlbinism (lack of skin pigmentation) is caused by a recessive autosomal allele. A man and woman, both normally pigmented, have an albino child together. The couple decides to have a second child. What is the probability that this child will be albino? A) 1 B) 1/2 C) 3/4 D) 1/4 E) 0
- 4. Open EndedThe mother is now pregnant for a third time, and her doctor tells her she is carrying fraternal twins. What is the probability that BOTH children will have normal pigmentation? A) 3/4 B) 9/16 C) 1/4 D) 16/16 E) 1/16
- 5. Open EndedThree babies were recently mixed up in a hospital. After consideration of the data below, which of the following represent the correct baby/parent combinations? Couple number I II III Blood Groups A and A A and B B and O Baby number 1 2 3 Blood Group B O AB A) I-2, II-1, III-3 B) I-3, II-1, III-2 C) I-1, II-3, III-2 D) I-3, II-2, III-1 E) I-2, II-3, III-1
- 6. Open EndedA woman who belongs to blood group A and is Rh positive has a daughter who is O positive and a son who is B negative. Rh positive is a simple dominant over Rh negative. Which of the following is a possible genotype for the son? A) IBiRr B) IBIBRR C) IBIBRr D) IBirr E) IBIBrr
- 7. Open EndedWhich of the following is a possible phenotype for the father? A) O positive B) O negative C) A positive D) A negative E) B positive
- 8. Open EndedWhite eyes is a sex-linked recessive characteristic in fruit flies. If a female having white eyes is crossed with a wild-type male, what percentage of the F1 females will have white eyes? A) 100% B) 0% C) 50% D) 75% E) 25%
- 9. Open EndedThe following is a map of four genes on a chromosome: Between which two genes would you expect the highest frequency of recombination? A) A and W B) A and G C) E and G D) W and E E) A and E
- 10. Open EndedUsing the letters (T, t) for the alleles, what is the genotype of individual C-1? a. TT b. Tt c. tt d. TT or tt e. TT or Tt
- 11. Open EndedAn achondroplastic male dwarf with color blindness marries a woman of normal height with normal vision. The man's father was six-feet tall, and both the woman's parents were of average height. The woman's father was color blind also. Achondroplastic dwarfism is autosomal dominant, and red-green color blindness is X-linked recessive. Begin by writing out the genotypes of the married couple. You have all the information you need in the question above. How many of their daughters might be expected to be color-blind dwarfs? a. one out of four b. none c. all d. three out of four e. half
- 12. Open EndedThey have a daughter who is a dwarf with normal color vision. What is the probability that she is heterozygous for both genes? a. 0.25 b. 0.75 c. 0.50 d. 0 e. 1.00
- 13. Open EndedA woman is found to have 47 chromosomes, including 3 X chromosomes. Which of the following describes her expected phenotype?
- 14. Open EndedIn cats, black fur color is caused by an X-linked allele; the other allele at this locus causes orange color. The heterozygote is tortoiseshell. What kinds of offspring would you expect from the cross of a black female and an orange male?
- 15. Open EndedRed-green color blindness is a sex-linked recessive trait in humans. Two people with normal color vision have a color-blind son. What are the genotypes of the parents?
- 16. Open EndedCinnabar eyes is a sex-linked recessive characteristic in fruit flies. If a female having cinnabar eyes is crossed with a wild-type male, what percentage of the F1 males will have cinnabar eyes?
- 17. Open EndedIn birds, sex is determined by a ZW chromosome scheme. Males are ZZ and females are ZW. A recessive lethal allele that causes death of the embryo is sometimes present on the Z chromosome in pigeons. What would be the sex ratio in the offspring of a cross between a male that is heterozygous for the lethal allele and a normal female?
- 18. Open EndedA man who is an achondroplastic dwarf with normal vision marries a color-blind woman of normal height. The man's father was six feet tall, and both the woman's parents were of average height. Achondroplastic dwarfism is autosomal dominant, and red-green color blindness is X-linked recessive. How many of their daughters might be expected to be color-blind dwarfs?
- 19. Open EndedWhat proportion of their sons would be color-blind and of normal height?
- 20. Open EndedThey have a daughter who is a dwarf with normal color vision. What is the probability that she is heterozygous for both genes?
- 21. Open EndedSex determination in mammals is due to the SRY region of the Y chromosome. An abnormality could allow which of the following to have a male phenotype?
- 22. Open EndedIn a series of mapping experiments, the recombination frequencies for four different linked genes of Drosophila were determined as shown in the figure. What is the order of these genes on a chromosome map?
- 23. Open EndedWhich of the following two genes are closest on a genetic map of Drosophila?
- 24. Open EndedGenes D and F could be A) located on different chromosomes. B) located very near to each other on the same chromosome. C) located far from each other on the same chromosome. D) Both A and B E) Both A and C
- 25. Open EndedIn humans, male-pattern baldness is controlled by an autosomal gene that occurs in two allelic forms. Allele Hn determines nonbaldness, and allele Hb determines pattern baldness. In males, because of the presence of testosterone, allele Hb is dominant over Hn. If a man and woman both with genotype HnHb have a son, what is the chance that he will eventually be bald?
- 26. Open EndedA phenotypically normal prospective couple seeks genetic counseling because the man knows that he has a translocation of a portion of his chromosome 4 that has been exchanged with a portion of his chromosome 12. Although he is normal because his translocation is balanced, he and his wife want to know the probability that his sperm will be abnormal. What is your prognosis regarding his sperm?
- 27. Open EndedA couple has a child with Down syndrome when the mother is 39 years old at the time of delivery. Which is the most probable cause?
- 28. Open EndedThe pedigree in Figure 15.4 shows the transmission of a trait in a particular family. Based on this pattern of transmission, the trait is most likely
- 29. Open EndedA certain kind of snail can have a right-handed direction of shell coiling (D) or left handed coiling (d). If direction of coiling is due to a protein deposited by the mother in the egg cytoplasm, then a Dd egg-producing snail and a dd sperm-producing snail will have offspring of which genotype(s) and phenotype(s)?
- 30. Open EndedIn certain plants, tall is dominant to short. If a heterozygous plant is crossed with a homozygous tall plant, what is the probability that the offspring will be short? A) 1 B) 1/2 C) 1/4 D) 1/6 E) 0
- 31. Open EndedTwo true-breeding stocks of pea plants are crossed. One parent has red, axial flowers and the other has white, terminal flowers; all F1 individuals have red, axial flowers. The genes for flower color and location assort independently. 48) Among the F2 offspring, what is the probability of plants with white axial flowers? A) 9/16 B) 1/16 C) 3/16 D) 1/8 E) 1/4
- 32. Open EndedIn some cats, black color is due to a sex-linked (X-linked) recessive gene (b); the dominant allele (B) produces orange color.The heterozygote (Bb) is calico.What kinds of offspring would be expected from the cross of an orange male and a black female? a) black females, orange males; b) orange females, black males; c) calico females, black males; d) black females, calico males; e) orange females and males.
- 33. Open EndedA couple has three children, all of whom have brown eyes and blond hair.Both parents are homozygous for brown eyes (BB), but one is blond (rr) and the other is a redhead (Rr).What is the probability that the next child will be a brown-eyed redhead? a) 1/16; b) 1/8; c) 1/4; d) 1/2; e) 1.
- 34. Open EndedIn humans, the allele for short fingers is dominant over that for long fingers.If a person with short fingers who had a parent with long fingers marries a person with long fingers, what are the chances for each child to have short fingers? a) zero; b) 25%; c) 50%; d) 75%; e) 100%.
- 35. Open EndedA blue-eyed, left-handed woman marries a brown-eyed, right handed man who is heterozygous for both traits.If blue eyes and left-handedness are recessive, how many different phenotypes are possible in their children? a) one; b) two; c) three; d) four; e) six; ab) eight; ac) nine; ad) too many.
- 36. Open EndedGray seed color in peas is dominant to white. Assume that Mendel conducted a series of experiments where plants with gray seeds were crossed among themselves, and the following progeny were produced: 302 gray and 98 white. (a) What is the most probable genotype of each parent? (b) Based on your answer in (a) above, what genotypic and phenotypic ratios are expected in these progeny? (Assume the following symbols: G = gray and g = white.) A) (a) GG . gg; (b) genotypic = 3:1, phenotypic = 1:2:1 B) (a) Gg . Gg; (b) genotypic = 1:2:1, phenotypic = 3:1 C) (a) GG . Gg; (b) genotypic = 1:2:1, phenotypic = 2:1 D) (a) gg . Gg; (b) genotypic = 1:2, phenotypic = 3:1
- 37. Open EndedA man has extra digits (six fingers on each hand and six toes on each foot). His wife and their daughter have a normal number of digits. Having extra digits is a dominant trait. The couple's second child has extra digits. What is the probability that their next (third) child will have extra digits? A) 1/2 B) 1/16 C) 1/8 D) 3/4
- 38. Open EndedPhenylketonuria is an inherited disease caused by a recessive autosomal allele. If a woman and her husband are both carriers, what is the probability that their first child will be a phenotypically normal girl? A) 1/4 B) 1/16 C) 3/16 D) 3/8
- 39. Open Ended32) Assuming independent assortment for all gene pairs, what is the probability that the following parents, AABbCc . AaBbCc, will produce an AaBbCc offspring? A) 1/2 B) 1/16 C) 1/8 D) 3/4
- 40. Open Ended) In rabbits, the homozygous CC is normal, Cc results in deformed legs, and cc results in very short legs. The genotype BB produces black fur, Bb brown fur, and bb white fur. If a cross is made between brown rabbits with deformed legs and white rabbits with deformed legs, what percentage of the offspring would be expected to have deformed legs and white fur? A) 25% B) 33% C) 100% D) 50%
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