1. Sex Linked Traits Humans have 23 pairs of chromosomes.
One pair of chromosomes is related to the sex of an individual , these chromosomes are called sex chromosomes

2. Sex Linked Traits
The other 22 pairs of chromosomes are called autosomes (1-22)

4. Sex Linked Traits
In humans, the sex of an individual depends on the presence or absence of the Y chromosome
A normal human female is XX
A normal human male is XY

6. (c = colorblind, C = normal)
Sex Linked Traits
Genes that are located on the X chromosome are called sex-linked genes.
Traits determined by sex-linked genes are called sex-linked traits
 (c = colorblind, C = normal)
Ex. Color blindness
female Xc Xc
male Xc Y

7. Sex Linked Traits
Most sex linked traits are recessive, this means both X chromosomes must have the gene in order for the trait to be expressed.

8. Sex Linked Traits
If only one X chromosome is present (in males)and has the sex linked gene, then the trait will be expressed

9. (C= normal, c= colorblind)
Carriers
A carrier is a person that has the trait on only one chromosome and does not express the trait. Carriers of sex linked traits are always women.
(C= normal, c= colorblind)
Ex. Color blind carrier XC Xc

10. Sex Linked Punnett Squares
A colorblind male marries a normal female. What are the offspring genotypes and phenotypes? (C = normal, c = colorblind)
Xc Y XC

11. Sex Linked Punnett Squares
A colorblind male marries a normal female. What are the offspring genotypes and phenotypes?
(C = normal, c = colorblind)
Xc Y
XC XC Xc XC Y
XC XC Xc XC Y

12. Sex Linked Punnett Squares
A normal male (not colorblind) marries a carrier. What are the offspring genotypes and phenotypes?
XC Y XC Xc

13. Sex Linked Punnett Squares
A normal male (not colorblind) marries a carrier. What are the offspring genotypes and phenotypes?
XC Y
XC XC XC XC Y
Xc Xc Xc Xc Y

14. Sex Linked Punnett Squares
A normal male (not colorblind) marries a colorblind female. What are the offspring genotypes and phenotypes?
XC Y Xc

15. Sex Linked Punnett Squares
A normal male (not colorblind) marries a colorblind female. What are the offspring genotypes and phenotypes?
XC Y
Xc XC Xc Xc Y

16. Hemophilia Hemophilia is characterized by uncontrolled bleeding
It is a sex linked disorder caused by errors in the DNA that codes for the proteins involved in clotting
Video – sex linked traits (1 minute)

17. Test #1
What are the sexes and eye colors of flies with the following genotypes?
X R X r _________ X R Y __________ X r X r __________
X R X R ____________ X r Y ____________

18. Answer #1
What are the sexes and eye colors of flies with the following genotypes?
X R X r female, red_ X R Y _male, red_ X r X r _female, white_
X R X R _female, red _ X r Y _male, white__

19. Test #2 What are the genotypes of these flies:
white eyed, male ____________
red eyed female (heterozygous) ________
white eyed, female ___________
red eyed, male ___________

20. Answer #2 What are the genotypes of these flies:
white eyed, male ___X r Y_____
red eyed female (heterozygous) _X R X r__
white eyed, female ___X r X r___
red eyed, male __X R Y____

21. Test #3
Show a cross between a pure red eyed female and a white eyed male. What are the genotypes of the parents:
______ and _________
How many are:
white eyed, male ____ white eyed, female __ red eyed, male ___ red eyed, female ____

22. Answer #3
Show a cross between a pure red eyed female and a white eyed male. What are the genotypes of the parents:
__X R X R____ and _____X r Y____
How many are:
white eyed, male __0__ white eyed, female _0_ red eyed, male _1/2__ red eyed, female _1/2___

23. Epistasis and Pleiotropy

24. Test #4
Show the cross of a red eyed female (heterozygous) and a red eyed male.
What are the genotypes of the parents?_______ & _____
How many are:
white eyed, male ____ white eyed, female ____ red eyed, male ____ red eyed, female ____
Math: What if in the above cross, 100 males were produced and 200 females. How many total red-eyed flies would there be?_________________

25. Answer #4
Show the cross of a red eyed female (heterozygous) and a red eyed male.
What are the genotypes of the parents?
___X R X r___ & ______X R Y_____
How many are:
white eyed, male _1/4_ white eyed, female _0_ red eyed, male __1/4__ red eyed, female _1/2_
Math: What if in the above cross, 100 males were produced and 200 females. How many total red-eyed flies would there be?_ = 250 total__

26. Test #5
In humans, hemophilia is a sex linked trait. Females can be normal, carriers, or have the disease. Males will either have the disease or not (but they won’t ever be carriers)
X H X H = female, normal X H X h = female, carrier X h X h = female, hemophiliac
X H Y = male, normal X h Y= male, hemophiliac
Show the cross of a man who has hemophilia with a woman who is a carrier. What is the probability that their children will have the disease? __________

27. Answer #5
In humans, hemophilia is a sex linked trait. Females can be normal, carriers, or have the disease. Males will either have the disease or not (but they won’t ever be carriers)
X H X H = female, normal X H X h = female, carrier X h X h = female, hemophiliac
X H Y = male, normal X h Y= male, hemophiliac
What is the probability that their children will have the disease? _1/4 (female) + 1/4 (males) or 2/4 total__

28. Test #6 A woman who is a carrier marries a normal man. Show the cross.
What is the probability that their children will have hemophilia?
What sex will a child in the family with hemophilia be?

29. Answer #6
A woman who is a carrier marries a normal man. Show the cross. What is the probability that their children will have hemophilia? What sex will a child in the family with hemophilia be?
¼ daughters normal, ¼ daughters carrier, ¼ sons normal, ¼ sons hemophilia

30. Test #7
A woman who has hemophilia marries a normal man. How many of their children will have hemophilia, and what is their sex?

31. Answer #7
A woman who has hemophilia marries a normal man. How many of their children will have hemophilia, and what is their sex?
all boys will have hemophilia

32. Test #8
In cats, the gene for calico (multicolored) cats is codominant. Females that receive a B and an R gene have black and oRange splotches on white coats. Males can only be black or orange, but never calico.
Here’s what a calico female’s genotype would look like: X B X R
Show the cross of a female calico cat with a black male?
What percentage of the kittens will be black and male? _________ What percentage of the kittens will be calico and male? _________ What percentage of the kittens will be calico and female? _________

33. Answer #8 Show the cross of a female calico cat with a black male?
What percentage of the kittens will be black and male? __1/4____ What percentage of the kittens will be calico and male? _0_____ What percentage of the kittens will be calico and female? _1/4_____

34. Test #9 Show the cross of a female black cat, with a male orange cat.
What percentage of the kittens will be calico and female? _____
What color will all the male cats be? ______

35. Answer #9
What percentage of the kittens will be calico and female? _2/4 (all females)___
What color will all the male cats be? _black_