Principles of Heredity
Probability, Phenotypes and Genotypes
__________________ 1. Suppose you toss a coin five times and each time it lands heads. What
is the probability the next toss will be heads?
__________________ 2. The probability of getting three tails in a row when tossing a coin is_?
__________________ 3. An organism has the genotype AaBB. The number of possible
combinations of alleles in gametes produced by this organism is ___.
__________________ 4. Mendel formulated the laws of dominance, segregation, and ___.
__________________ 5. A pure tall plant TT, is crossed with a pure short plant, tt. The expected
genotype(s) among their offspring is (are) ______.
__________________ 6. A plant has the genotype Ww. The probable distribution of alleles in
this plant’s gametes is
__________________ 7. The factors or characters described by Mendel are today called __.
__________________ 8. When F2 plants showed a ratio of 3 round: 1 wrinkled seeds, Mendel
concluded that ______ was a dominant trait.
_________________ 9.
The genotype (s) expected from a cross of TT x tt is (are)
__________________ 10. A gamete contains ______ allele(s) for each trait.
In a certain Plant, the gene for yellow seeds, Y is dominant to the gene for green seeds, y.
Use this information to answer the following questions.
__________________ 11. What is the genotype of a heterozygous plant?
__________________ 12. What is the genotype of a homozygous yellow-seeded plant?
__________________ 13. What is the genotype of a green-seeded plant?
__________________ 14. What is the phenotype of a plant with two dominant genes?
__________________ 15. What is the phenotype of a plant with one dominant and one
recessive gene?
__________________ 16. Crosses between F1 individuals resulting from the cross AABB x aabb
lead to F2 phenotypic ratios close to _____________.
__________________17. One gene has alleles A and a. Another has alleles B and b. For the
following genotype, what type of gametes will be produced? Aabb
18. A dominant allele B gives rise to Black fur in cats and b gives white fur. Fred has a black
cat and a white cat. He wants to know the genotype of his black cat. What should he do
and why?
19. A recessive allele a is responsible for albinism, an inability to produce or deposit melanin
in tissues. Humans and some other organisms can have this phenotype. In each of the
following cases, what are the possible genotypes of the father, of the mother, and of their
children?
a. both parents have normal phenotypes; some of their children are albino and others
are unaffected.
b. both parents are albino and have only albino children.
c. the woman is unaffected, the man is albino, and they have one albino child and
three unaffected children. (What gives rise to this 3:1 ratio?)
20. Create a simple pedigree of the family in 19c. Make sure you show generation and
individual numbers.
21. The trait for shell color in northern horned beetles is controlled by co-dominant
inheritance. R – red shell color G – green shell color. In a cross between a solid Red beetle
and a Red and Green spotted beetle 275 offspring were created. How many beetles would
you expect to have solid red shells, spotted shells, and solid green shells?
22. A recessive allele on the X chromosome is responsible for red-green color blindness in
humans. A woman with normal vision whose father is color-blind marries a color-blind male.
What is the probability that this couple’s son will be color-blind?
23. A man that carries an X-linked allele will pass it on to
a. all of his daughters. B. half of his daughters.
d. half of his sons
e. all of his children
C. all of his sons
24. A Barr body (the condensed inactive X) is normally found in the nucleus of which kind of
human cell?
a. unfertilized egg cells only
b. sperm cells only
c. somatic cells of a female
d. somatic cells of the male
e. both male and female somatic cells.
25. In cats, black color is caused by an X-linked allele; the other allele at this locus causes
orange color. The heterozygote is tortoiseshell. What kinds of offspring would you expect
from the cross of a black female and an orange male? Include gender and coat color.
26. If a chromosome lacks certain genes, what type of chromosomal mutation has most likely
occurred?
27. A mouse with gray coat color is mated with a female of the same phenotype. Among
their offspring 30 mice were gray, 12 were black, and 16 were white. What is the simplest
explanation for the inheritance of these colors in mice? What offspring would your predict
from the mating of a grey mouse and a black mouse?
28. A woman who belongs to the blood group A and in Rh + has a daughter who is O + and
a son who is B -. Rh+ is simple dominant over Rh-.
a. Write a possible genotype for the son.
b. Write a possible genotype for the mother.
c. What is a possible phenotype for the father?
29.Huntington’s disease is caused by a dominant allele. If one of your parents has the
disease, what is the probability that you, too, will have the disease?
30. Pink flower color in snapdragons is controlled by incomplete dominance inheritance (Rr).
Explain how you would create a true-breeding pink flowered snapdragon.