Original Document: X Linked Genes
**In fruit flies, eye color is a sex linked trait. Red is dominant to white.**
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__
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____
3. Show the cross of a white eyed female X r X r with a red-eyed male X R Y .
Results in all red eyed females, and all white eyed males
4. 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 ____
white eyed, female __
red eyed, male _1/2__
red eyed, female _1/2___
5. 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 __
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__
6. 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? _1/4 (female) + 1/4 (males) or 2/4 total__
7. 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? 1/4, only boys8. 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, or half of their children
9. 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? __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_____
10. Show the cross of a female black cat, with a male orange cat.
What percentage of the kittens will be calico and female? _2/4 (all females)___What color will all the male cats be? _black_