Question 1

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)  1:1 
D)  1:1:1:1

Question 2

What is the probability of producing the genotype AABBCC in a cross of individuals who both possess this genotype: AaBbCc?

Accepted Answer

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

Question 3

The 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

Question 4

Mendel's law of independent assortment has its basis in which of the following events of meiosis I?

Accepted Answer

A)  synapsis of homologous chromosomes 
B)  crossing over of homologous pairs of chromosomes 
C)  alignment of pairs of homologous chromosomes along the middle of the cell 
D)  the division of cells at telophase

Question 5

Which of the following statements is correct in describing 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 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. 
C)  A monohybrid cross is performed for one generation, whereas a dihybrid cross is performed for two generations. 
D)  A monohybrid cross results in a 9:3:3:1 ratio, whereas a dihybrid cross gives a 3:1 ratio.

Question 6

Albinism is a recessive trait. A man and woman both show normal pigmentation, but both have one parent who has albinism (without melanin pigmentation). What is the probability that their first child will have albinism?

Accepted Answer

A)  0 
B)  1/2 
C)  1/4 
D)  1

Question 7

Feather color in budgies is determined by two different genes, Y for pigment on the outside of the feather, and B for pigment on the inside of the feather. YYBB, YyBB, or YYBb is green; yyBB or yyBb is blue; YYbb or Yybb is yellow; and yybb is white. Two blue budgies were crossed. Over the years, they produced 22 offspring, five of which were white. What are the most likely genotypes for the two blue budgies?

Accepted Answer

A)  yyBB and yyBB 
B)  yyBB and yyBb 
C)  yyBb and yyBb 
D)  yyBb and yybb

Question 8

Radish flowers may be red, purple, or white. A cross between a red-flowered plant and a white-flowered plant yields all-purple offspring. The part of the radish we eat may be oval or long, with long being the dominant trait. If true-breeding red long radishes are crossed with true-breeding white oval radishes, the F₁ will be expected to exhibit which of the following phenotypes?

Accepted Answer

A)  red and long 
B)  white and long 
C)  purple and long 
D)  purple and oval

Question 9

Which of the following scenarios describes an example of epistasis?

Accepted Answer

A)  Recessive genotypes for each of two genes (aabb) results in an albino corn snake. 
B)  In rabbits and many other mammals, one genotype (ee) prevents any fur color from developing. 
C)  In Drosophila (fruit flies), white eyes can be due to an X-linked gene or to a combination of other genes. 
D)  In cacti, there are several genes for the type of spines.

Question 10

Which of the following statements best describes the addition rule of probability?

Accepted Answer

A)  the probability that two or more independent events will occur simultaneously 
B)  the probability that either one of two independent events will occur 
C)  the probability of producing two or more heterozygous offspring 
D)  the likelihood that a trait is due to two or more meiotic events

Question 11

Assuming independent assortment for all gene pairs, what is the probability that a cross between the following parents, AABbCc × AaBbCc, will produce an AaBbCc offspring?

Accepted Answer

A)  1/2 
B)  1/16 
C)  1/8 
D)  3/4

Question 12

In some parts of Africa, the frequency of heterozygosity for the sickle-cell anemia allele is unusually high, presumably because this reduces the frequency of malaria. Such a relationship is related to which of the following?

Accepted Answer

A)  Mendel's law of independent assortment 
B)  Mendel's law of segregation 
C)  Darwin's explanation of natural selection 
D)  the malarial parasite changing the allele

Question 13

Gene S controls the sharpness of spines in a type of cactus. Cacti with the dominant allele, S, have sharp spines, whereas homozygous recessive ss cacti 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% sharp-spined, 50% dull-spined progeny 
C)  25% sharp-spined, 50% dull-spined, 25% spineless progeny 
D)  It is impossible to determine the phenotypes of the progeny.

Question 14

What was the most significant conclusion that Gregor Mendel drew from his experiments with pea plants?

Accepted Answer

A)  There is considerable genetic variation in garden peas. 
B)  Traits are inherited in discrete units and are not the result of "blending." 
C)  Recessive genes occur more frequently in the F₁ generation than do dominant ones. 
D)  Genes are composed of DNA.

Question 15

Use the figure and the following description to answer the question.
In a particular plant, leaf color is controlled by gene locus D. Plants with at least one allele D have dark green leaves, and plants with the homozygous recessive dd genotype have light green leaves. A true-breeding, dark-leaved plant is crossed with a light-leaved one, and the F₁ offspring is allowed to self-pollinate. The predicted outcome of the F₂ is diagrammed in the Punnett square shown in the figure, where 1, 2, 3, and 4 represent the genotypes corresponding to each box within the square.

Which of the boxes marked 1-4 correspond to plants with a heterozygous genotype?

Accepted Answer

A)  1 
B)  1, 2, and 3 
C)  2 and 3 
D)  2, 3, and 4

Question 16

The following question refers to the pedigree chart in the figure for a family, some of whose members exhibit the dominant trait, W. Affected individuals are indicated by a dark square or circle.

What is the genotype of individual II-5?

Accepted Answer

A)  WW 
B)  Ww 
C)  ww 
D)  ww or Ww

Question 17

Use the figure and the following description to answer the question.
In a particular plant, leaf color is controlled by gene locus D. Plants with at least one allele D have dark green leaves, and plants with the homozygous recessive dd genotype have light green leaves. A true-breeding, dark-leaved plant is crossed with a light-leaved one, and the F₁ offspring is allowed to self-pollinate. The predicted outcome of the F₂ is diagrammed in the Punnett square shown in the figure, where 1, 2, 3, and 4 represent the genotypes corresponding to each box within the square.

Which of the boxes marked 1-4 correspond to plants with dark leaves?

Accepted Answer

A)  1 only 
B)  2 and 3 
C)  4 only 
D)  1, 2, and 3

Question 18

Which of the following inheritance patterns 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 19

Given the following genotypes for two parents, AABBCc × AabbCc, assume that all traits exhibit simple dominance and independent assortment. What proportion of the progeny of this cross will be expected to phenotypically resemble the first parent with the genotype AABBCc?

Accepted Answer

A)  1/4 
B)  3/4 
C)  3/8 
D)  1

Question 20

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 is completely dominant over the allele for pink hydrangea 
C)  the alleles are codominant 
D)  environmental factors such as soil pH affect the phenotype

Exam 14: Mendel and the Gene Idea