Dihybrid Practice

You are performing a dihybrid cross with two traits encoded by two different genes. These genes are on two different chromosomes and follow the Law of Independent Assortment. The two parental genotypes are AABB and aabb. The genotype of all F1 plants is AaBb. What phenotype ratio will you observe in the F2 generation?
1. 8:4:2:1
2. 1:1:1:1
3. 9:3:3:1
4. 1:2:2:1
A scientist is studying the inheritance of two traits: stem height and stem color. Tall is dominant over short; brown is dominant over green. The scientist wants to do a test cross to determine the genotype of a tall, brown F1 hybrid individual. What will be the height and color of the other plant he uses in this test cross?
1. Tall and brown
2. Short and green
3. Short and brown
4. It doesn’t matter; any of the above will work.
A cross between two individuals results in a ratio of 9:3:3:1 for four possible phenotypes. This is an example of a
1. dihybrid cross.
2. monohybrid cross.
3. testcross.
4. none of these.
Human height shows a continuous variation from the very short to the very tall. Height is most likely controlled by
1. epistatic genes.
2. environmental factors.
3. sex-linked genes.
4. multiple genes.
A pea plant is heterozygous for both seed shape and seed color. S is the allele for the dominant, spherical shape characteristic; s is the allele for the recessive, dented shape characteristic. Y is the allele for the dominant, yellow color characteristic; y is the allele for the recessive, green color characteristic. What will be the distribution of these two alleles in this plant's gametes?
1. 50% of gametes are Sy; 50% of gametes are sY
2. 25% of gametes are SY; 25% of gametes are Sy;
  25% of gametes are sY; 25% of gametes are sy.
3. 50% of gametes are sy; 50% of gametes are SY
4. 100% of the gametes are SsYy
A phenotype ratio of 9:3:3:1 in the offspring of a mating of two organisms heterozygous for two traits is expected when:
1. the genes reside on the same chromosome
2. each gene contains two mutations
3. the gene pairs assort independently during meiosis
4. only recessive traits are scored
Which of the following genetic crosses would be predicted to give a phenotypic ratio of 9:3:3:1?
1. SSYY x ssyy
2. SsYY x SSYy
3. SsYy x SsYy
4. SSyy x ssYY
The gametes of a plant of genotype SsYy should have the genotypes:
1. Ss and Yy
2. SY and sy
3. SY, Sy, sY, and sy
4. . Ss, Yy, SY and sy
Which of the following genotypes would you not expect to find among the offspring of a SsYy x ssyy test cross:
1. ssyy
2. SsYy
3. ssYy
4. SsYY
The expected phenotypic ratio of the progeny of a SsYy x ssyy test cross is:
1. 9:3:3:1.
2. 3:1.
3. 1:1:1:1.
4. 3:1:1:3.
In a dihybrid cross, AaBb x AaBb, what fraction of the offspring will be homozygous for both recessive traits?
1. 1/16
2. 1/8
3. 3/16
4. 1/4
Following a SsYy x SsYy cross, what fraction of the offspring are predicted to have a genotype that is heterozygous for both characteristics?
1. 1/16
2. 3/16
3. 4/16
4. 9/16
In a dihybrid cross, SsYy x SsYy, what fraction of the offspring will be homozygous for both traits?
1. 1/16
2. 1/8
3. 1/4
4. 3/4
If Mendel's crosses between tall, spherical-seeded plants and short, dented-seeded plants had produced many more than 1/16 short, dented-seeded plants in the F2 generation, he might have concluded that:
1. the dented seed and short traits are unlinked.
2. all traits in peas assort independently of each other.
3. the spherical seed and tall traits are linked.
4. all traits in peas are linked.
In Mendel's experiments, the spherical seed character (SS) is completely dominant over the dented seed character (ss). If the characters for height were incompletely dominant, such that TT are tall, Tt are intermediate and tt are short, what would be the phenotypes resulting from crossing a spherical-seeded, short (SStt) plant to a dented-seeded, tall (ssTT) plant?
1. All the progeny would be spherical-seeded and tall.
2. 1/2 would be spherical-seeded and intermediate height; 1/2 would be spherical-seeded and tall.
3. You cannot predict the outcome.
4. All the progeny would be spherical-seeded and intermediate height.
Two unlinked loci effect mouse hair color. CC or Cc mice are agouti. Mice with genotype cc are albino because all pigment production and deposition of pigment in hair is blocked. At the second locus, the B allele (black agouti coat) is dominant to the b allele (brown agouti coat). A mouse with a black agouti coat is mated with an albino mouse of genotype bbcc. Half of the offspring are albino, one quarter are black agouti, and one quarter are brown agouti. What is the genotype of the black agouti parent?
1. BBCC
2. BbCc
3. bbCC
4. BbCC
Two unlinked loci effect mouse hair color. AA or Aa mice are agouti. Mice with genotype aa are albino because all pigment production is blocked, regardless of the phenotype at the second locus. At the second locus, the B allele (agouti coat) is dominant to the b allele (black coat). What would be the result of a cross between two agouti mice of genotype AaBb?
1. 4 agouti: 4 black: 8 albino
2. 9 agouti: 3 black: 4 albino
3. 8 agouti: 4 black: 4 albino
4. 9 agouti: 3 black: 3 albino: 1 grey
An organism of genotype AaBb can make gametes of all the following kinds except
1. AB
2. Bb
3. aB
4. ab
Whenever a capital letter is present, a red color is produced. In a cross of AaBb x AaBb, how many red offspring would you expect out of 16?
1. 1
2. 3
3. 9
4. 15
Assume that you mated two individuals heterozygous for each of two traits and obtained 80 offspring. How many of them would be expected to look like their parents?
1. 25
2. 45
3. 60
4. 80
If W = purple flower and w = white, and D = tall plants and d = short plants, a wwDd plant would be
1. purple and tall
2. purple and short
3. white and tall
4. white and short
If two true-breeding parents are crossed with each other and all the offspring have their mother's ears and their father's tail, the parents in the cross would be
1. EETT x eett
2. eeTT x EEtt
3. EeTt x EeTt
4. eeTt x Eet
If aaBb is crossed with AAbb, what proportion of the offspring will be AAbb?
1. 0
2. 3/16
3. 9/16
4. 1/4
If AaBb is crossed with AaBb, what proportion of the offspring will be dominant for the 'A/a' trait and recessive for the 'B/b' trait (i.e. A-bb)?
1. 0
2. 3/16
3. 9/16
4. 1/16

Dihybrid Practice

Multiple-choice review quiz