1) What do we mean when we use the terms monohybrid cross and dihybrid cross?
C) A dihybrid cross involves organisms that are heterozygous for two characters, and a monohybrid cross involves only one.
2) What was the most significant conclusion that Gregor Mendel drew from his experiments with pea plants?
B) Traits are inherited in discrete units, and are not the results of "blending."
3) How many unique gametes could be produced through independent assortment by an individual with the genotype AaBbCCDdEE?
B) 8
4) The individual with genotype AaBbCCDdEE can make many kinds of gametes. Which of the following is the major reason?
D) different possible assortment of chromosomes into gametes
5) Why did Mendel continue some of his experiments to the F2 or F3 generation?
B) to observe whether or not a recessive trait would reappear
6) Which of the following differentiates between independent assortment and segregation?
A) The law of independent assortment requires describing two or more genes relative to one another.
7) Two plants are crossed, resulting in offspring with a 3:1 ratio for a particular trait. What does this suggest?
D) that the parents were both heterozygous for a single trait
8) A sexually reproducing animal has two unlinked genes, one for head shape (H) and one for tail length (T). Its genotype is HhTt. Which of the following genotypes is possible in a gamete from this organism?
E) HT
9) 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?
C) 50%
10) Mendel accounted for the observation that traits that had disappeared in the F1 generation reappeared in the F2 generation by proposing that
C) traits can be dominant or recessive, and the recessive traits were obscured by the dominant ones in the F1.
11) The fact that all seven of the pea plant traits studied by Mendel obeyed the principle of independent assortment most probably indicates which of the following?
D) All of the genes controlling the traits behaved as if they were on different chromosomes.
12) Mendel's observation of the segregation of alleles in gamete formation has its basis in which of the following phases of cell division?
D) anaphase I of meiosis
14) Why did the F1 offspring of Mendel's classic pea cross always look like one of the two parental varieties?
D) One allele was dominant.
13) Mendel's second law of independent assortment has its basis in which of the following events of meiosis I?
C) alignment of tetrads at the equator
15) Black fur in mice (B) is dominant to brown fur (b). Short tails (T) are dominant to long tails (t). What fraction of the progeny of crosses BbTt × BBtt will be expected to have black fur and long tails?
D) 1/2
16) In certain plants, tall is dominant to short. If a heterozygous plant is crossed with a homozygous tall plant, what is the probability that the offspring will be short?
E) 0
17) In the cross AaBbCc × AaBbCc, what is the probability of producing the genotype AABBCC?
E) 1/64
18) Given the parents AABBCc × AabbCc, assume simple dominance for each trait and independent assortment. What proportion of the progeny will be expected to phenotypically resemble the first parent?
C) 3/4
19) Which of the following is the best statement of the use of the addition rule of probability?
C) the probability that either one of two independent events will occur
20) Which of the following calculations require that you utilize the addition rule?
D) Calculate the probability of a child having either sickle-cell anemia or cystic fibrosis if parents are each heterozygous for both.
21) Marfan syndrome in humans is caused by an abnormality of the connective tissue protein fibrillin. Patients are usually very tall and thin, with long spindly fingers, curvature of the spine, sometimes weakened arterial walls, and sometimes ocular problems, such as lens dislocation.
Which of the following would you conclude about Marfan syndrome from this information?
D) It is pleiotropic.
22) 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?
B) roan × roan
23) Which of the following describes the ability of a single gene to have multiple phenotypic effects?
C) pleiotropy
24) Cystic fibrosis affects the lungs, the pancreas, the digestive system, and other organs, resulting in symptoms ranging from breathing difficulties to recurrent infections. Which of the following terms best describes this?
C) pleiotropy
25) Which of the following is an example of polygenic inheritance?
E) skin pigmentation in humans
26) 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?
E) environmental factors such as soil pH
27) Which of the following provides an example of epistasis?
C) In rabbits and many other mammals, one genotype (ee) prevents any fur color from developing.
28) A scientist discovers a DNA-based test for one allele of a particular gene. This and only this allele, if homozygous, produces an effect that results in death at or about the time of birth. Of the following, which is the best use of this discovery?
B) Design a test for identifying heterozygous carriers of the allele.
29) 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?
C) Darwin's explanation of natural selection
30) One of two major forms of a human condition called neurofibromatosis (NF 1) is inherited as a dominant gene, although it may range from mildly to very severely expressed. If a young child is the first in her family to be diagnosed, which of the following is the best explanation?
B) One of the parents has very mild expression of the gene.
Two true-breeding stocks of pea plants are crossed. One parent has red, axial flowers and the other has white, terminal flowers; all F1 individuals have red, axial flowers. The genes for flower color and location assort independently.
1) If 1,000 F2 offspring resulted from the cross, approximately how many of them would you expect to have red, terminal flowers?
B) 190
Two true-breeding stocks of pea plants are crossed. One parent has red, axial flowers and the other has white, terminal flowers; all F1 individuals have red, axial flowers. The genes for flower color and location assort independently.
2) Among the F2 offspring, what is the probability of plants with white axial flowers?
C) 3/16
Labrador retrievers are black, brown, or yellow. In a cross of a black female with a brown male, results can be either all black puppies, 1/2 black to 1/2 brown puppies, or 3/4 black to 1/4 yellow puppies.
3) These results indicate which of the following?
E) Epistasis is involved.
Labrador retrievers are black, brown, or yellow. In a cross of a black female with a brown male, results can be either all black puppies, 1/2 black to 1/2 brown puppies, or 3/4 black to 1/4 yellow puppies.
4) How many genes must be responsible for these coat colors in Labrador retrievers?
B) 2
Labrador retrievers are black, brown, or yellow. In a cross of a black female with a brown male, results can be either all black puppies, 1/2 black to 1/2 brown puppies, or 3/4 black to 1/4 yellow puppies.
5) In one type cross of black × black, the results were as follows:
9/16 black
4/16 yellow
3/16 brown
The genotype eebb must result in which of the following?
C) yellow
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.
6) If true-breeding red long radishes are crossed with true-breeding white oval radishes, the F1 will be expected to be which of the following?
D) purple and long
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.
7) In the F2 generation of the above cross, which of the following phenotypic ratios would be expected?
E) 6:3:3:2:1:1
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.
8) The flower color trait in radishes is an example of which of the following?
D) incomplete dominance
Drosophila (fruit flies) usually have long wings (+), but mutations in two different genes can result in bent wings (bt) or vestigial wings (vg).
9) If a homozygous bent wing fly is mated with a homozygous vestigial wing fly, which of the following offspring would you expect?
A) all +bt +vg heterozygotes
Drosophila (fruit flies) usually have long wings (+), but mutations in two different genes can result in bent wings (bt) or vestigial wings (vg).
10) If flies that are heterozygous for both the bent wing gene and the vestigial wing gene are mated, what is the probability of offspring with bent wings only?
E) 3/16
Tallness (T) in snapdragons is dominant to dwarfness (t), and red (R) flower color is dominant to white (r). The heterozygous condition results in pink (Rr) flower color.
11) A dwarf, red snapdragon is crossed with a plant homozygous for tallness and white flowers. What are the genotype and phenotype of the F1 individuals?
D) TtRr–tall and pink
Tallness (T) in snapdragons is dominant to dwarfness (t), and red (R) flower color is dominant to white (r). The heterozygous condition results in pink (Rr) flower color.
12) If snapdragons are heterozygous for height as well as for flower color, a mating between them will result in what ratio?
B) 6:3:3:2:1:1
Skin color in a certain species of fish is inherited via a single gene with four different alleles.
13) How many different types of gametes would be possible in this system?
C) 4
14) One fish of this type has alleles 1 and 3 (S1S3) and its mate has alleles 2 and 4 (S2S4). If each allele confers a unit of color darkness such that S1 has one unit, S2 has two units, and so on, then what proportion of their offspring would be expected to have five units of color?
D) 1/2
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.
15) The relationship between genes S and N is an example of
B) epistasis.
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.
16) A cross between a true-breeding sharp-spined cactus and a spineless cactus would produce
A) all sharp-spined progeny.
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.
17) If doubly heterozygous SsNn cactuses were allowed to self-pollinate, the F2 would segregate in which of the following ratios?
E) 9 sharp-spined:3 dull-spined:4 spineless
Feather color in budgies is determined by two different genes, Y and B, one for pigment on the outside and one for 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.
18) A blue budgie is crossed with a white budgie. Which of the following results is not possible?
D) green and yellow offspring
19) Two blue budgies were crossed. Over the years, they produced 22 offspring, 5 of which were white. What are the most likely genotypes for the two blue budgies?
Feather color in budgies is determined by two different genes, Y and B, one for pigment on the outside and one for 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.
C) yyBb and yyBb
A woman who has blood type A positive has a daughter who is type O positive and a son who is type B negative. Rh positive is a trait that shows simple dominance over Rh negative and is designated by the alleles R and r, respectively. A third gene for the MN blood group has codominant alleles M and N.
20) Which of the following is a possible partial genotype for the son?
D) I^Bi
A woman who has blood type A positive has a daughter who is type O positive and a son who is type B negative. Rh positive is a trait that shows simple dominance over Rh negative and is designated by the alleles R and r, respectively. A third gene for the MN blood group has codominant alleles M and N.
21) Which of the following is a possible genotype for the mother?
D) IAi
22) Which of the following is a possible phenotype for the father?
C) B positive
23) If both children are of blood type M, which of the following is possible?
A) Each parent is either M or MN.
Humanoids on the newly explored planet Brin (in a hypothetical galaxy in ~50 years from the present) have a gene structure similar to our own, but many very different plants and animals.
24) One species of a small birdlike animal has an extremely variable tail length, an example of polygenic inheritance. Geneticists have come to realize that there are eight separate genes for tail length per haploid genome, with each gene having two alleles. One allele for each gene (a1, b1, and so on) increases the length by 1 cm, whereas the other allele (a2, b2, and so on) increases it by 0.5 cm. One bird was analyzed and found to have the following genotype: a1a1b2b2c1c2d1d2e2e2f1f2g1g1h1h2
What is the length of its tail?
C) 12 cm
Humanoids on the newly explored planet Brin (in a hypothetical galaxy in ~50 years from the present) have a gene structure similar to our own, but many very different plants and animals.
25) One species of green plant, with frondlike leaves, a spine-coated stem, and purple cup-shaped flowers, is found to be self-pollinating. Which of the following is true of this species?
D) Some of the seeds would have true-breeding traits.
26) If the environmental parameters, such as temperature, humidity, atmosphere, sunlight, and so on, are mostly Earthlike, which of the following do you expect of its types of leaves, stems, and flowers?
E) Phenotypes would be selected for or against by these environmental factors.