1. For each of the diploid genotypes presented below, determine the genetic make up for all of the possible gametes that would result through the process of meiosis. Remember, each egg or sperm must have one of each other. That letter can be upper or lower case.
a. Rr = RR, Rr, Rr, rr
b. RrYy = RY, Yr, Ry, yr
c. rrYy = Yr, Yr, yr, yr
d. RrYY = RY, RY, Yr, Yr
2. For each of the following, state whether the genotype of a diploid or haploid cell is represented.
a. D = haploid
b. GG = diploid
c. P = haploid
d. ee = diploid
3. Yellow guinea pigs crossed with white ones always produce cream colored offspring. Two cream colored guinea pigs when crossed produced yellow, cream and white offspring in the ratio of 1 yellow: 2 cream: 1 white. Explain how are these colors inherited. No calculations needed! Name the type of inheritance this represents.
A cream colored guinea pig has the inherited alleles of one yellow parent and one white parent which makes it YW. When two cream colored guinea pigs cross it is then YW, YW. This produces one yellow (YY), two creams (YW) and one white (WW). This type of inheritance is called incomplete dominance because the cream color is the "intermediate" between yellow and white, with neither being dominant.
4. In sheep white is due to a dominant gene (B), black to its recessive allele (b). A white ewe mated to a white ram produces a black lamb. What are the genotypes of the parents? You might need to construct Punnet squares experimenting with different crosses to come up with this answer. Name the type of inheritance this represents.
The genotypes of the parents must be Bb for each sheep. With one dominant white gene and one recessive black gene. This would have a 1/4 chance of producing a black sheep, by getting two recessive genes (bb). This type of inheritance is called dominant-recessive inheritance.
5. In peas, yellow color (G) is dominant to green color (g). A heterozygous yellow is crossed with a green. What is the expected phenotype ratio of the offspring? Name the type of inheritance this represents.
This would result in Gg, gg, Gg, gg. So one half is Gg (yellow) and one half is gg (green). This is an example of dominant-recessive inheritance.
6. White color (Y) is dominant to yellow color (y) in squash. A heterozygous white fruit plant is crossed with a yellow fruit plant. What is the expected phenotype ratio of the offspring? What is this type of inheritance called?
Half will be Yy (white) and half will be yy (yellow). This type of inheritance is called dominant-recessive.
7. In certain flowers, a cross between homozygous red and a homozygous white will always result in a pink flower. A cross is made between two pink flowers. What is the predicted phenotype ratio of the colors red, pink and white appearing in the offspring? What is this type of inheritance called?
The phonotype ratio will be one white, two pink, and one red. This type of inheritance is called incomplete dominance.
8. In humans, the condition for normal blood clotting dominates the condition for non-clotting or hemophilia. Both alleles are lined to the X chromosome. A male hemophiliac marries a woman who is a carrier for this condition. In this respect, a carrier is a woman who has an allele for normal blood clotting and an allele for hemophilia. What are the chances that if they have a male child he will be normal for blood clotting? What is this type of inheritance called?
The child will have a 50% chance of inheriting hemophilia. This is called dominant-recessive inheritance.
9. A person with an allele for type A blood and type O blood marries someone with an allele for type B blood and type O blood. List the types of offspring they cold have and the probability for each blood type in the offspring. (A allele = 1^A, B allele = 1^B, O allele = i) What is the expected phenotype ratio of the offspring? What is the type of inheritance called?
The offspring could be A, B, AB or O blood type. The probability of each type of blood is 25% A, 25% B, 25%AB, and 25% O. This type of inheritance is called codominance.
10. Skin color in humans becomes darker by the number of dominant alleles; AABBCC have the darkest skin and aabbcc have the lights skin. Place these genotypes in sequence according to the color of skin expected for each. Place the darkest skin first. What is this type of inheritance called?
AaBBCC
AaBBCc
AaBbCc
AAbbcc
aabbcc
This type of inheritance is called polygenic inheritance.
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