Download Read Chatper 14 and do the following genetics problems

AP Biology: Genetics Problems
1. Some laboratory mice are spotted, due to a dominant gene. Solid color is recessive. A solid
color female lab mouse is mated to a spotted male. Both parents are homozygous. What
percentage of spotted mice should be found in the litter?
2. Horticulturists are attempting to breed a rare and beautiful variety of pine tree, where all the
branches droop gracefully to the ground, rather than extend outward in the normal manner.
Drooping branches are recessive, and the normal variety is due to a dominant gene. What
percentage of the drooping variety will be produced by crossing two heterozygous pines?
3. In German Shepards, the drooping ear trait is due to a dominant gene, while erect ears is due
to a recessive allele. If two heterozygous dogs with drooping ears are mated, will any of the pups
be likely to have drooping ears? If so, what percentage can be expected?
4. In iguanas, warty tails is a recessive characteristic which sometimes appears. The normal tail
has smooth skin. If a warty tailed iguana is mated to a homozygous smooth iguana, will any of
their offspring have warts? Why or why not?
5. Blonde hair is due to a recessive gene, while brown hair is dominant. Agnes has brown hair,
but her mother was a blonde. Ralph, her husband, has brown hair also, and his father was blonde.
Is it possible for Ralph and Agnes to have blonde children? If so, what percentage?
6. Type AB blood is an example of co-dominance where both genes produce a part of the blood
type. It is due to receiving an "a" gene from one parent and a "b" gene from the other parent. If
two people marry who have type AB blood, what blood types can they expect in their children?
What are the chances of each of these blood types occurring in their children?
7. If a type O person (recessive) marries a type AB person, what blood types could occur in their
children? Remember, Type O is recessive to both A and B.
8. In humans type A blood is dominant to type O blood. John has type A blood. His mother was
type O. Martha also has type A blood. Both of her parents were type A, also. Their first child has
type O blood. John had biology in high school and he thinks that Martha was unfaithful to him
since he remembers that type A blood is due to a dominant gene, and since he also has type A
blood he thinks that any child they have must be type A. Is John correct? Explain.
9. There is a rare genetic trait called sickle-cell anemia which is due to an incompletely dominant
gene. Persons who suffer this genetic disease have misshaped blood cells, suffer severe pain and
frequently die prematurely. However, these symptoms only occur when the person has two
sickle-cell genes. Heterozygous individuals usually have no symptoms since the normal gene
causes production of enough normal hemoglobin, and of course, persons with two normal genes
are asymptomatic as well. If two people marry who are heterozygous for the sickle-cell trait,
what are the chances that any of their children will have two genes for sickle-cell anemia?
10. Roan is the name for a peculiar color in cows and horses which is a mixture of rust- red and
white. It is the result of incomplete dominance and both alleles have an effect on the phenotype.
When a red cow is mated to a white bull, all the offspring will be roan. If two roans are crossed,
will all their offspring be roan? Explain.
11. In morning glory flowers, red petals and white petals are also due to incompletely dominant
genes. Hybrid individuals are pink. If a red morning glory is crossed to a pink one, what colors
and percentages of each color will be produced?
12. Radish roots may be long or round or oval. The oval shape is due to receiving a long and a
round gene from the parent radishes. A farmer plants a crop of radishes which all came from
seeds of the same two parents. When the crop is harvested,he counts 2023 long radishes, 1997
round ones, and 4011 oval . What were the genotypes and phenotypes of the parents ?
AP Biology Dihybrid problems
1. Gregor Mendel discovered that wrinkled peas result from a dominant gene and smooth peas
are produced by recessive genes. Also,tall vines are dominant while short vines are recessive.
The genes for vine height is on a different pair of chromosomes than the gene for pea coat. If a
homozygous tall, homozygous wrinkled pea plant is crossed to a short smooth plant, what will be
the phenotypes and genotypes of the offspring? If two of the offspring are crossed, what will be
the ratio of phenotypes in the F2 generation? Show your work.
2. In hounds, drooping ears is dominant to erect ears. Also barking while trailing rabbits is
dominant to silent trailers. What kind of pups can be expected from a cross between a
heterozygous droop-eared barker mated to a erect eared silent trailer?
3. In humans, blood type A and B are incompletely dominant, while blood type O is recessive to
both A and B. On another chromosome pair, Rh + factor is dominant, while Rh- is recessive.
Raoul is type A and Rh +. His mother is Type O, Rh-. He marries Drusilda, who is type AB, Rh . What kind of blood types can their kids have?
4. In mice black color fur is dominant to brown color fur. Also there is a recessive gene for
albino, which prevents the expression of both the black and brown fur genes. The albino locus is
on a different chromosome than the black and brown locus. If two mice are crossed which are
heterozygous black, and carry the recessive albino gene but are normally pigmented, what is the
phenotype ratio which may be expected from numerous crosses from these parents?
5. In peas, Mendel discovered that White flowers are dominant to red flowers. Also, axial
flowers are dominant to terminal flowers. If a homozygous white, axial flowered plant is crossed
with a red, terminal flowerd plant, what will be the genotype and phenotype of the offspring?
What will be the genotypes and phenotypes of the F2 generation, and in what proportion?
6. In Drosophila, grey body and long wings are dominant to ebony body and vestigial wings. If a
heterozygous grey, heterozygous long winged fly is mated to an ebony, vestigial winged fly,
what will be the genotypes and phenotypes of the offspring?
7. In guinea pigs black fur is dominant to white fur and short fur is dominant to long. If two
guinea pigs heterozygous for both traits are mated, what will be the genotypes and phenotypes of
the offspring?
AP Sex-linked Genetics Problems
1. White eyed fruit flies are the result of a sex-linked recessive gene. Show the results from a
cross between a red-eyed male and a white-eyed female Drosophila. Indicate the results of each
sex separately.
2. A young lady comes to you for advice in your capacity as a marriage counselor. She tells you
that her brother has hemophilia, but both her parents are normal. She wishes to marry a man who
has no history of hemophilia in her family, and wants to know the probability of her children
having the disease. What should you tell her?
3. If a man who is color-blind is married to a woman who is normal (and not a carrier), will any
of their children have a chance of being color-blind?
4. In cats there is a pair of alleles for coat color which is intermediate and sex-linked. There is
one gene for yellow fur and one gene for black fur, but the heterozygote has a peculiar mixture
of both colors called tortoise shell. What type of kittens would result from a cross between a
black female and a yellow male. If one of the offspring, when matured, is crossed to the male
parent, what offspring would result?
5. A man sues his wife for divorce on the grounds of infidelity. Both man and wife have normal
eyes, but the first daughter has coloboma iridis, a fissure in the iris of the eye. The character is
known to be inherited as a sex-linked recessive. If you were the man's lawyer, could you use
these facts as evidence? Explain.
6. A color-blind woman marries a normal man. What kind of children may they expect?