Inheritance Problems
Some aliens have the following traits:
Trait
Body color
Number of Antennae
Eye color
Eyesight
Number of Body Rings
1.
2.
8.
9.
10.
11.
12.
13.
14.
15.
16.
17.
18.
19.
Dominant Phenotype
(Y) Yellow
(A) 2
(P) Purple
(E) Glasses needed
(R) 3
Recessive Phenotype
(y) Orange
(a) 1
(p) White
(e) Glasses not worn
(r) 5
A heterozygous male mates with a pure yellow female. What is the chance this couple will produce an orange baby?
Two purple-eyed aliens mate. Both aliens are heterozygous for the eye color trait. What is the chance this couple will produce
a baby with a homozygous recessive genotype?
3. A heterozygous female with 3 body rings mates with a 5-ringed male. What is the chance that this couple will have a baby
that looks like its mother?
4. A pure male alien displaying the dominant body color mates with a female that is homozygous recessive for this
characteristic. What is the chance that this couple will have a baby with a heterozygous genotype?
5. A male alien with 1 antenna mates with a female alien who has 2 antennae. The female is heterozygous for the antenna trait.
What is the chance that this couple will produce a baby with the recessive phenotype?
6. An alien couple, both of which wear glasses, are having a baby. The male’s genotype is heterozygous. The female is
phenotypically dominant but does carry the recessive allele. What is the chance that this couple’s baby will have to wear
glasses?
7. A 3-ringed female mates with a homozygous male. The female has been genetically tested and is carrying both the dominant
and the recessive allele for this trait. The male displays the recessive phenotype. What is the chance that this couple will have
a homozygous baby?
In peas red flowers are dominant over white flowers. A pea plant with white flowers is crossed with one that has red flowers; of
the progeny 147 have white flowers and 161 have red flowers. What are the genotypes of the two parent plants?
In peas red flowers (R) are dominant over white flowers (r). Two plants that had red flowers were crossed. There were 76 plants
with red flowers and 24 plants with white flowers in the F1 generation. What was the genotype of the two parents.
Assume that white is the dominant color over yellow in squash. If pollen from the anthers of a heterozygous white-fruited plant is
placed on the pistil of a yellow-fruited plant, show, using ratios, the genotypes and phenotypes you would expect the seeds from
the cross to produce.
Jim did not have bent little fingers, but his mother did. Rosie, his wife had bent little fingers. Rosie's mother did not have bent
little fingers. What are the chances that they will have kids with bent little fingers? A dominant allele (B) causes the last joint of
the little finger to bend inward towards the fourth (ring) finger. Individuals whose little fingers are straight possess the
homozygous recessive condition, bb.
Both Count Dracula and Natasha are heterozygous for widow's peak. What are the chances that their son Igor will also have
widow's peak? The dominant allele (W) causes the hairline to form a V-shape point in the middle of the forehead. A person who is
homozygous recessive has a straight hair line.
George has attached ear lobes. Barbara has free earlobes, but she is heterozygous for this trait. What are the chances of their child
having free earlobes? The inheritance of a dominant gene E results in the free or unattached earlobe. If the lobe is attached
directly to the head, the individual is homozygous recessive, and the ee genotype is present.
The allele for Huntington's Chorea is dominant. Woody Guthrie was heterozygous for this trait and Mrs. Guthrie did not have
Huntington's Chorea. What are the chances that their son Arlo will develop this disease?
When Ralph folded his arms, he always placed his left arm on top of the right. His mother always placed her right arm on top
when she folded her arms. When Boopsie folded her arms, she always positioned her right arm on top of the left. Ralph and
Boopsie are having a child....it is a girl. Which way will this girl position her arms when she folds them. Placing the left arm on
top of the right is due to a dominant allele (A). Placing the right arm on top is due to a recessive allele (aa).
The allele for Tay-Sachs is recessive. The Tay-Sachs genetic testing program has enabled Bernie to determine that he is a
carrier....he has a recessive allele for Tay-Sachs......... (and that his wife, Beverly, is not). What are the changes that they could
have a child with Tay-Sachs?
Persons who are heterozygous for sickle cell anemia are said to have the sickle trait. What are the chances that Sam and his wife
Ethyl, who both have the trait, will have a child with sickle cell anemia (homozygous recessive).
John can roll his tongue, but his mother cannot. He also has attached earlobes. He marries Marsha, who cannot roll her tongue but
has free earlobes. Marsha's father, however, has attached earlobes. What are the chances that their child will have free earlobes
and be able to roll its tongue?
Roger is homozygous for Huntington's and has cystic fibrosis. Elvira is homozygous normal for Huntington's but a carrier of
cystic fibrosis. Cystic fibrosis is inherited via a recessive allele. What are the chances that their child has neither Huntington's nor
cystic fibrosis?
20. Both Willy and Ethyl are heterozygous for earlobe attachment and also for hitchhiker's thumb. What are the chance of a child
with ....attached earlobes and a hitchhiker's thumb? ......free earlobes and no hitchhiker's thumb?
21. In Guinea pigs rough coat (fur) texture and black coat (fur) are dominant. A rough-coated, black guinea pig, whose mother was
smooth and white is mated with a smooth, white animal. What kinds of offspring would they produce and in what relative
numbers?
22. A rough, black guinea pig bred with a rough, white one gives 28 rough, black; 31 rough, white; 11 smooth, black, and 9 smooth
white. Give the genotypes for the parents and each offspring.
23. Two rough black guinea pigs when bred together have two offspring, one of them rough white and the other smooth, black. If
these same parents were to be bred together further, what offspring would you expect from them.
24. A purple, smooth Jimson weed plant crossed with white, spiny one gives 320 purple, spiny and 312 purple smooth. If these two
types of offspring are bred together, what will their offspring be like, both as to appearance and as to genotype.
25. Color-blindness is a sex-linked recessive. A girl of normal vision whose father was color-blind married a color blind boy. What
type of vision will be expected in their children?
26. Two normal-visioned parents produce a color-blind son. What are the genotypes of the parents? What are the chances of their
next child being a color-blind daughter?
27. A woman of normal vision, whose father was color-blind, marries a man of normal vision whose maternal grandfather was colorblind. What type of vision will be expected in their children? Color-blindness is sex linked recessive.
28. Yellow body (y)...the recessive allele in Drosophila is a sex-linked allele recessive to gray body (Y)...the dominant allele. A
certain gray female mated with an unknown male produced some yellow and some gray offspring of both sexes. What was the
genotype of the original female? What was the phenotype of the male to which she was mated?
29. A female fruit fly with sable body (s) is mated with a male having gray body (S). Their daughters are gray, their sons sable. In
what chromosomes is the S gene?
30. Albino pigmentation in humans is due to autosomal linked homozygous recessive. Hemophilia is sex linked recessive. An albino,
non-hemophilic man marries a normally-pigmented, non-hemophilic woman whose father was hemophilic and whose mother was
an albino. What kinds of children can they have and in what proportions?
31. A woman whose maternal grandfather suffered from hemophilia has parents that are normal. The woman's husband is normal.
She has a hemophiliac son. What is the chance that the next son will be normal? Will any of the daughters be hemophiliac? Will
any be carriers? Hemophilia is X-linked recessive.
47. Fred is type A and his father is type O. Wilma is type B and her father was type O. The Rh blood group is not linked to the ABO
system. It is a two allele group, with positive dominant to negative. Fred is positive, but his mother is negative. Wilma is also
negative. What are the chances that "Pebbles," Fred and Wilma's daughter, will be AB negative
48. In human beings, migraine (a type of sick headache) is due to a dominant factor. A normal vision woman who has never suffered
from migraine takes her daughter to the doctor for an examination. In the course of the examination the doctor discovers that the
girl is color-blind, and suffers from migraine. What does the doctor automatically know about the father?
49. In humans, brown eyes (B) are dominant over blue (b)*. A brown-eyed man marries a blue-eyed woman and they have three
children, two of whom are brown-eyed and one of whom is blue-eyed. Draw the Punnett square that illustrates this marriage.
What is the man’s genotype? What are the genotypes of the children? (* Actually, the situation is complicated by the fact
that there is more than one gene involved in eye color, but for this example, we’ll consider only this one gene.)
50. In gerbils, the wild type body color is Agouti (brown). There are several genes which contribute to that color, and different alleles
for some of these genes can cause unusual fur colors. One of these genes has a rare mutant allele which causes the fur to be a
lighter, redder color, called copper. This gene has two alleles, its wild type (brown) and copper. Brown is completely dominant to
copper. You are going to mate two brown gerbils (call them Betty and Bert). Both Betty’s mother and Bert’s mother were copper
colored.
a. What color were Betty’s father and Bert’s father?
b. What is Betty’s genotype? What about Bert’s?
c. What genotypic ratio should this mating produce?
d. What phenotypic ratio should this mating produce?
e. Assume you now allow Betty and Bert to mate. Betty eventually has eight babies, five brown and three copper. Does this
agree with the prediction you made (your phenotypic ratio)? If not, what do you think went wrong?
51. This involves the same gerbil gene as the first scenario. You have another brown gerbil, Gertrude. You know nothing about
Gertrude’s family history. If you want to figure out whether Gertrude is homozygous or heterozygous for this gene, what kind of
gerbil should you choose to mate her to, and why?
52. Curled ears in cats is caused by a mutated gene and has been developed into a breed, known as the
American Curl. A cat with curled ears was mated with a cat with normal ears and all of the offspring have
curled ears. Is this trait dominant or recessive? What is the genotype of the curled eared cat?
If one of the kittens from the above cross was mated to a cat normal ears what percentage of the offspring will
have curled ears?
53. In cats B allele produces black fur and b produces orange fur. This gene is X linked. If both alleles are present calico cats
are produced. A calico cat has 2 calico kittens, 1 male black kitten, and 1 female orange kitten.
a. What is the genotype of the mother__________phenotype____________
b.
What is the genotype of the father____________phenotype___________
54. Label all the genotypes for the following pedigree.
a.
Is this trait dominant or recessive?
b.
How do you know?
55. Albinism in humans is caused by the inheritance of a pair of recessive autosomal alleles (aa). Use the given
family pedigree to solve the following problems.
I
1
2
II
1
2
1
2
3
4
5
6
III
3
4
5
IV
7
1
2
3
4
6
8
5
7
9
8
10
11
9
10
11
12
13
14
12
15
13
16
14
17
15
18
6
a. What are the genotypes of IV1, IV3, IV4, and IV11? _____.
b. What are the genotypes of III2, III3, III7, and III8? _____
c. Assuming II4 is AA, what is the probability that III4 is heterozygous for albinism? _____%
d. What is the probability that IV6 is homozygous for normal pigmentation? _____%
56. Label the genotypes for this pedigree of an X-linked recessive disorder (red-green colorblindness).