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

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

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

(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

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.

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

(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

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

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

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

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

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

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

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)

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 ____________

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__

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

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____

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 ____

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___

Epistasis and Pleiotropy

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?_________________

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?_50 + 200 = 250 total__

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? __________

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__

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?

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

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

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

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? _________

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_____

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? ______

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_