Question 1

In rabbits, the homozygous CC is normal, Cc results in deformed legs, and cc results in very short legs. The genotype BB produces black fur, Bb brown fur, and bb white fur. If a cross is made between brown rabbits with deformed legs and white rabbits with deformed legs, what percentage of the offspring would be expected to have deformed legs and white fur?

Accepted Answer

A)  25 percent 
B)  33 percent 
C)  about 66 percent 
D)  100 percent 
E)  50 percent

Question 2

When Thomas Hunt Morgan crossed his red-eyed F1 generation flies to each other, the F2 generation included both red- and white-eyed flies. Remarkably, all the white-eyed flies were male. What was the explanation for this result?

Accepted Answer

A)  The gene involved is on the Y chromosome. 
B)  The gene involved is on the X chromosome. 
C)  The gene involved is on an autosome, but only in males. 
D)  Other male-specific factors influence eye color in flies. 
E)  Other female-specific factors influence eye color in flies.

Question 3

Which of the following describes the ability of a single allele to have multiple phenotypic effects?

Accepted Answer

A)  incomplete dominance 
B)  multiple alleles 
C)  pleiotropy 
D)  epistasis

Question 4

The accompanying figure shows the pedigree for a family. Dark-shaded symbols represent individuals with one of the two major types of colon cancer. Numbers under the symbols are the individual's age at the time of diagnosis. Males are represented by squares, females by circles.  From this pedigree, this trait seems to be inherited ________.

Accepted Answer

A)  from mothers 
B)  as an autosomal recessive 
C)  as a result of epistasis 
D)  as an autosomal dominant 
E)  as an incomplete dominant

Question 5

When Mendel crossed yellow-seeded and green-seeded pea plants, all the offspring were yellow seeded. When he took these F1 yellow-seeded plants and crossed them to green-seeded plants, what genotypic ratio was expected?

Accepted Answer

A)  1:2:1 
B)  3:1 
C)  9:3:3:1 
D)  1:1 
E)  1:1:1:1

Question 6

Two plants are crossed, resulting in offspring with a 3:1 ratio for a particular trait. This ratio suggests that ________.

Accepted Answer

A)  the parents were true-breeding for contrasting traits 
B)  the particular trait shows incomplete dominance 
C)  a blending of traits has occurred 
D)  the parents were both heterozygous for the particular trait 
E)  each offspring has the same alleles for each of two different traits

Question 7

The individual with genotype AaBbCCDdEE can make many kinds of gametes. Which of the following is the major reason?

Accepted Answer

A)  segregation of maternal and paternal alleles 
B)  recurrent mutations forming new alleles 
C)  crossing over during prophase I 
D)  different possible assortment of chromosomes into gametes 
E)  the tendency for dominant alleles to segregate together

Question 8

Different ratios occur in crosses with single gene pairs or two gene pairs. What types of ratios are likely to occur in crosses dealing with a single gene pair?

Accepted Answer

A)  9:3:3:1, 1:2:1 
B)  1:1:1:1, 1:4:6:4:1 
C)  3:1, 1:1, 1:2:1 
D)  4:1, 1:1, 1:4:1

Question 9

Gene S controls the sharpness of spines in a type of cactus. Cactuses with the dominant allele, S, have sharp spines, whereas homozygous recessive ss cactuses have dull spines. At the same time, a second gene, N, determines whether or not cactuses have spines. Homozygous recessive nn cactuses have no spines at all. If doubly heterozygous SsNn cactuses were allowed to self-pollinate, the F2 would segregate in which of the following ratios?

Accepted Answer

A)  3 sharp-spined:1 spineless 
B)  1 sharp-spined:2 dull-spined:1 spineless 
C)  1 sharp-spined:1 dull-spined:1 spineless 
D)  1 sharp-spined:1 dull-spined 
E)  9 sharp-spined:3 dull-spined:4 spineless

Question 10

Mendel's observation of the segregation of alleles in gamete formation has its basis in which of the following phases of cell division?

Accepted Answer

A)  prophase I of meiosis 
B)  anaphase II of meiosis 
C)  metaphase II of meiosis 
D)  anaphase I of meiosis 
E)  anaphase of mitosis

Question 11

Hydrangea plants of the same genotype are planted in a large flower garden. Some of the plants produce blue flowers and others pink flowers. This can be best explained by which of the following?

Accepted Answer

A)  the knowledge that multiple alleles are involved 
B)  the allele for blue hydrangea being completely dominant 
C)  the alleles being codominant 
D)  the fact that a mutation has occurred 
E)  environmental factors such as soil pH

Question 12

In the cross AaBbCc × AaBbCc, what is the probability of producing the genotype AABBCC?

Accepted Answer

A)  1/4 
B)  1/8 
C)  1/16 
D)  1/32 
E)  1/64

Question 13

When crossing an organism that is homozygous recessive for a single trait with a heterozygote, what is the chance of producing an offspring with the homozygous recessive phenotype?

Accepted Answer

A)  0 percent 
B)  25 percent 
C)  50 percent 
D)  75 percent 
E)  100 percent

Question 14

Radish flowers may be red, purple, or white. The part of the radish we eat may be oval or long. A cross between a red-flowered long radish plant and a white-flowered oval radish plant yields all-purple long radish offspring. Then the F1 are crossed. In the resulting F2 generation, which of the following phenotypic ratios would be expected?

Accepted Answer

A)  9:3:3:1 
B)  9:4:3 
C)  1:1:1:1 
D)  1:1:1:1:1:1 
E)  6:3:3:2:1:1

Question 15

In cats, black fur 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?

Accepted Answer

A)  tortoiseshell females; tortoiseshell males 
B)  black females; orange males 
C)  orange females; orange males 
D)  tortoiseshell females; black males 
E)  orange females; black males

Question 16

In cattle, roan coat color (mixed red and white hairs) occurs in the heterozygous (Rr) offspring of red (RR) and white (rr) homozygotes. Which of the following crosses would produce offspring in the ratio of 1 red:2 roan:1 white?

Accepted Answer

A)  red × white 
B)  roan × roan 
C)  white × roan 
D)  red × roan 
E)  The answer cannot be determined from the information provided.

Question 17

Gray seed color in peas is dominant to white. Assume that Mendel conducted a series of experiments where plants with gray seeds were crossed among themselves, and the following progeny were produced: 302 gray and 98 white.
(a) What is the most probable genotype of each parent?
(b) Based on your answer in (a) above, what genotypic and phenotypic ratios are expected in these progeny? (Assume the following symbols: G = gray and g = white.)

Accepted Answer

A)  (a) GG × gg; (b) genotypic = 3:1, phenotypic = 1:2:1 
B)  (a) Gg × Gg; (b) genotypic = 1:2:1, phenotypic = 3:1 
C)  (a) GG × Gg; (b) genotypic = 1:2:1, phenotypic = 2:1 
D)  (a) gg × Gg; (b) genotypic = 1:2, phenotypic = 3:1 
E)  (a) Gg × Gg; (b) genotypic = 3:1, phenotypic = 9:3:3:1

Question 18

Cinnabar eyes is a sex-linked, recessive characteristic in fruit flies. If a female having cinnabar eyes is crossed with a wild-type male, what percentage of the F1 males will have cinnabar eyes?

Accepted Answer

A)  0 percent 
B)  25 percent 
C)  50 percent 
D)  75 percent 
E)  100 percent

Question 19

What do we mean when we use the terms "monohybrid cross" and "dihybrid cross"?

Accepted Answer

A)  A monohybrid cross involves a single parent, whereas a dihybrid cross involves two parents. 
B)  A monohybrid cross produces a single progeny, whereas a dihybrid cross produces two progeny. 
C)  A dihybrid cross involves organisms that are heterozygous for two characters that are being studied, and a monohybrid cross involves organisms that are heterozygous for only one character being studied. 
D)  A monohybrid cross is performed for one generation, whereas a dihybrid cross is performed for two generations. 
E)  A monohybrid cross results in a 9:3:3:1 ratio, whereas a dihybrid cross gives a 3:1 ratio.

Question 20

Gene S controls the sharpness of spines in a type of cactus. Cactuses with the dominant allele, S, have sharp spines, whereas homozygous recessive ss cactuses have dull spines. At the same time, a second gene, N, determines whether or not cactuses have spines. Homozygous recessive nn cactuses have no spines at all. A cross between a true-breeding sharp-spined cactus and a spineless cactus would produce ________.

Accepted Answer

A)  all sharp-spined progeny 
B)  50 percent sharp-spined, 50 percent dull-spined progeny 
C)  25 percent sharp-spined, 50 percent dull-spined, 25 percent spineless progeny 
D)  all spineless progeny 
E)  It is impossible to determine the phenotypes of the progeny.

Exam 14: Mendel and the Gene

When Thomas Hunt Morgan crossed his red-eyed F1 generation flies to each other, the F2 generation included both red- and white-eyed flies. Remarkably, all the white-eyed flies were male. What was the explanation for this result?

Which of the following describes the ability of a single allele to have multiple phenotypic effects?

When Mendel crossed yellow-seeded and green-seeded pea plants, all the offspring were yellow seeded. When he took these F1 yellow-seeded plants and crossed them to green-seeded plants, what genotypic ratio was expected?

Two plants are crossed, resulting in offspring with a 3:1 ratio for a particular trait. This ratio suggests that ________.

The individual with genotype AaBbCCDdEE can make many kinds of gametes. Which of the following is the major reason?

Different ratios occur in crosses with single gene pairs or two gene pairs. What types of ratios are likely to occur in crosses dealing with a single gene pair?

Mendel's observation of the segregation of alleles in gamete formation has its basis in which of the following phases of cell division?

Hydrangea plants of the same genotype are planted in a large flower garden. Some of the plants produce blue flowers and others pink flowers. This can be best explained by which of the following?

In the cross AaBbCc × AaBbCc, what is the probability of producing the genotype AABBCC?

When crossing an organism that is homozygous recessive for a single trait with a heterozygote, what is the chance of producing an offspring with the homozygous recessive phenotype?

In cats, black fur 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?

In cattle, roan coat color (mixed red and white hairs) occurs in the heterozygous (Rr) offspring of red (RR) and white (rr) homozygotes. Which of the following crosses would produce offspring in the ratio of 1 red:2 roan:1 white?

Cinnabar eyes is a sex-linked, recessive characteristic in fruit flies. If a female having cinnabar eyes is crossed with a wild-type male, what percentage of the F1 males will have cinnabar eyes?

What do we mean when we use the terms "monohybrid cross" and "dihybrid cross"?