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Name____________________
Date_______________pd____
Monohybrid Crosses WS #1
Genetic Problems
A.
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2.
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4.
In cats, black fur (B) is dominant over white fur(b).
What is the symbol for the dominant trait?__________
What is the symbol for the recessive trait?__________
What are the two possible genotypes for a black cat?__________ and __________
What is the only genotype for a white cat?____________
B. A black female cat is mated with a white male cat. All four kittens are black.
5. What is the dominant trait?_______________
6. What is the symbol for the dominant trait?_________
7. What is the recessive trait?_______________
8. What is the symbol for the recessive trait?_________
9. What is the genotype of the white male?_____________
10. What gene did all the kittens inherit from the father?________
11. What gene did all the kittens inherit from the mother in order to be black?_________
12. What is the only genotype for the mother that would give all black kittens?_________
13. Is the mother cat homozygous or heterozygous?
14. Is the father cat homozygous or heterozygous?
15. Are the kittens homozygous or heterozygous?
16. What is the genotype of the kittens?
C. Another black female cat is mated to the white male. Four kittens result from this
new feline fling. Two kittens are white, two kittens are black.
17. Work out the cross for these two parents. Use the cross to answer questions 18-29.
18. What is the dominant trait?________
19. What is the symbol for the dominant trait?_________
20. What is the recessive trait?________
21. What is the symbol of the recessive trait?_________
22. What is the genotype of the white male?__________
23. What gene do you know the black mother cat has?________
24. What gene did each kitten inherit from the father?________
25. What gene did the two black kittens inherit from the mother in order to be
black?_______
26. What is the genotype of the black kittens?__________
27. What gene did the white kittens have to inherit from the mother to be
white?__________
28. What is the genotype of the white kittens?_________
29. What is the mother cat’s full genotype?___________
D. In humans, the ability to taste the chemical phenylthiocarbonide is a dominant trait
(T). People who cannot taste the chemical are called non-tasters and exhibit the
recessive phenotype (t). Lola returns to Atlanta with her four-year old daughter,
and is bringing child support charges against her old boyfriend Herman. Lola claims
Herman is the father of the child. Herman claims that he is not the perpetrator
and denies his fatherhood of the child. Lola is a non-taster, Herman is a nontaster, and the child is a taster.
30. What is the dominant trait?___________
31. What is the symbol for the dominant trait?___________
32. What is the recessive trait?____________
33. What is the symbol of the recessive trait?___________
34. What is Lola’s genotype?___________
35. What is Herman’s genotype?___________
36. Work out the cross between these two characters, and list the possible offspring they
could produce.
37. According to the cross, what is the probability of the producing a non-taster
child?______
38. What is the probability of the two producing a taster child?___________
39. Which person is lying about all the hanky-panky?__________________
E. In humans, brown eye color (B) is dominant to blue eye color (b). A brown eyed male
marries a brown eyed female. They have a child that has blue eyes.
40. What is the symbol for brown eyes?______________
41. What is the symbol for blue eyes?_______________
42. What is the genotype of the child?______________
43. What gene do both parents have in order to produce
a child with blue eyes?__________
44. What gene do both parents have in order for them to have brown eyes?_____________
45. What is the complete genotype for both the mother and father?___________________
46. What would be the genotype of a brown eyed girl whose father had blue eyes?_________
F. Offspring of two parents are all heterozygous for brown eyes.
47. What is the genotype of one parent?_______________
48. What is the genotype of the other parent?___________
49. What is the genotypes of the children?___________
50. Fill out the cross to prove your answer.