Download Who`s Colorblind - Net Start Class

Name ________________
Date _________________
Who’s Colorblind?....and other problems with sex and genetics
SEX-LINKED TRAITS
1. In humans, muscular dystrophy is a recessive sex-linked trait. A female carrier of this trait marries a normal male.
Show the cross.
Parent genotypes: ________ X ________
F1 genotypic ratio: __________________
F1 phenotypic ratio: _________________
2. What are the chances that their daughters will be carriers?_______________________________
3. What are the chances that their daughters will have muscular dystrophy? __________________
4. What are the chances that their sons will have muscular dystrophy? ______________________
5. In humans, hemophilia is recessive and sex-linked. A woman carrier marries a normal male.
Parent genotypes: ________ X ________
F1 genotypic ratio: __________________
F1 phenotypic ratio: _________________
6. What are the chances of normal females (not carriers)?___________
7. What are the chances of normal males? ___________
8. What are the chances of carrier females? ___________
9. What are the chances of males with hemophilia? _____________
10. The male offspring from the above problem that has hemophilia marries a carrier female.
Parent genotypes: ________ X ________
F1 genotypic ratio: __________________
F1 phenotypic ratio: _________________
11. What are the chances of having normal females (not carriers)? _____________
12. What are the chances that the females will be carriers?________________
13. What are the chances that females will have hemophilia?________________
14. What are the chances of normal males?_________________
15. What are the chances of males with hemophilia?________________
16. For some reason (not yet understood) more male babies are conceived than female. By childhood, the number of
boys and girls is the same. What is a possible explanation for the higher mortality (both before and after birth) of
male babies? ________________________________________________________________________________________
____________________________________________________________________________________________________
17. Why is it not possible for a male to be heterozygous for color-blindness? ___________________________________
___________________________________________________________________________________________________
18. In humans, color-blindness is recessive and sex-linked. Cross a normal woman whose father was color-blind and
whose mother was normal with a man who is color-blind.
Parent genotypes: ________ X ________
F1 genotypic ratio: __________________
F1 phenotypic ratio: _________________
19. What are the chances that their children will be color-blind? ________________
20. What are the chances that their children will be carriers? _________________
21. What are the chances that their children will be normal? _______________
Not all sex-linked genes are recessive. For example, hypophosphatemia is caused by a dominant allele on the X
chromosome.
22. Using A to represent the allele for hypophosphatemia, draw a Punnett square that shows the possible offspring of
a woman with genotype XAXa and a man with the genotype XaY.
Parent genotypes: ________ X ________
F1 genotypic ratio: __________________
F1 phenotypic ratio: _________________
23. What percentage of the children would be likely to have hypophosphatemia? _________________________
24. Are males more likely to have hypophosphatemia than females? Yes or
No
25. Explain. ___________________________________________________________________________________________
26. In a Punnett square, show the possible offspring of a woman with normal phenotype and a man with
hypophosphatemia. Give both ratios.
Parent genotypes: ________ X ________
F1 genotypic ratio: __________________
F1 phenotypic ratio: _________________
27. What percentage of the children would likely have hypophosphatemia? ________________
28. What percentage of the male offspring would likely have hypophosphatemia? _____________
29. Explain this result. ___________________________________________________________________________________
SEX-INFLUENCED TRAITS
30. It is often said that men inherit baldness from their maternal grandfathers via their mothers. In light of what you
have learned about this trait, is this a valid statement?
Yes
or
No
31. Explain. ___________________________________________________________________________________________
32. In men, the gene for baldness acts as a dominant gene and in women it acts as a recessive gene. A bald man
whose father was not bald marries a non-bald woman whose mother was bald. What are the chances of their
having a bald daughter. ____________________________________________
33. What are the chances of their having a bald son? ____________________
34. What are the chances of having a normal son? ______________________
In humans, the ring finger may be longer or shorter that the index finger. Short index finger is thought to be produced
by a gene which is dominant in men and recessive in women. What kinds of children and with what frequency would
the following marriages likely produce?
35. long fingered man X short-fingered woman? _________________________________________
36. heterozygous short-fingered man X heterozygous long-fingered woman? ______________________________
37. heterozygous short-fingered man X short-fingered woman? __________________________________
BONUS:
38. A woman’s father is color-blind. Two of her brothers, as well as an uncle on her mother’s side, are hemophiliacs.
What are the possible genotypes of all the individuals mentioned?__________________________________________
_____________________________________________________________________________________________________
39. If the woman had a hemophiliac son, what must be her genotype? _________________________________________
40. What are the chances that a sister of the hemophiliac son is a carrier of hemophilia? _________________________
41. If the woman’s husband is color-blind, what are the chances of a color-blind sister of her hemophiliac son being a
carrier of hemophilia? ________________________________________________________________________________
42. What are the chances that a non-color-blind sister is a carrier of hemophilia? ________________________________