Chapter 11 Mendel and the Gene Idea

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. B) The law of segregation requires describing two or more genes relative to one another. C) The law of segregation requires having two or more generations to describe. D) The law of independent assortment is accounted for by observations of prophase I. E) The law of segregation is accounted for by anaphase of mitosis.

A) The law of independent assortment requires describing two or more genes relative to one another.

Drosophila (fruit flies) usually have long wings (+), but mutations in two different genes can result in bent wings (bt) or vestigial wings (vg). 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 B) 1/2 bent and 1/2 vestigial flies C) all homozygous + flies D) 3/4 bent to 1/4 vestigial ratio E) 1/2 bent and vestigial to 1/2 normal

A) all +bt +vg heterozygotes

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

A) all sharp-spined progeny.

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. If 1,000 F2 offspring resulted from the cross, approximately how many of them would you expect to have red, terminal flowers? A) 65 B) 190 C) 250 D) 565 E) 750

B) 190

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. How many genes must be responsible for these coat colors in Labrador retrievers? A) 1 B) 2 C) 3 D) 4 E) 5

B) 2

How many unique gametes could be produced through independent assortment by an individual with the genotype AaBbCCDdEE? A) 4 B) 8 C) 16 D) 32 E) 64

B) 8

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? A) Screen all newborns of an at-risk population. B) Design a test for identifying heterozygous carriers of the allele. C) Introduce a normal allele into deficient newborns. D) Follow the segregation of the allele during meiosis. E) Test school-age children for the disorder.

B) Design a test for identifying heterozygous carriers of the allele.

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? A) The mother carries the gene but does not express it at all. B) One of the parents has very mild expression of the gene. C) The condition skipped a generation in the family. D) The child has a different allele of the gene than the parents.

B) One of the parents has very mild expression of the gene.

What was the most significant conclusion that Gregor Mendel drew from his experiments with pea plants? A) There is considerable genetic variation in garden peas. B) Traits are inherited in discrete units, and are not the results of "blending." C) Recessive genes occur more frequently in the F1 generation than do dominant ones. D) Genes are composed of DNA. E) An organism that is homozygous for many recessive traits is at a disadvantage.

B) Traits are inherited in discrete units, and are not the results of "blending."

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. The relationship between genes S and N is an example of A) incomplete dominance. B) epistasis. C) complete dominance. D) pleiotropy. E) codominance.

B) epistasis.

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

B) roan × roan

Why did Mendel continue some of his experiments to the F2 or F3 generation? A) to obtain a larger number of offspring on which to base statistics B) to observe whether or not a recessive trait would reappear C) to observe whether or not the dominant trait would reappear D) to distinguish which alleles were segregating E) to be able to describe the frequency of recombination

B) to observe whether or not a recessive trait would reappear

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. Among the F2 offspring, what is the probability of plants with white axial flowers? A) 9/16 B) 1/16 C) 3/16 D) 1/8 E) 1/4

C) 3/16

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

C) 3/4

Skin color in a certain species of fish is inherited via a single gene with four different alleles. How many different types of gametes would be possible in this system? A) 1 B) 2 C) 4 D) 8 E) 16

C) 4

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? A) 0% B) 25% C) 50% D) 75% E) 100%

C) 50%

What do we mean when we use the terms monohybrid cross and dihybrid cross? 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, and a monohybrid cross involves only one. 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.

C) A dihybrid cross involves organisms that are heterozygous for two characters, and a monohybrid cross involves only one.

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

C) Darwin's explanation of natural selection

Which of the following provides an example of epistasis? A) Recessive genotypes for each of two genes (aabb) result in an albino corn snake. B) The allele b17 produces a dominant phenotype, although b1 through b16 do not. C) In rabbits and many other mammals, one genotype (ee) prevents any fur color from developing. D) In Drosophila (fruit flies), white eyes can be due to an X-linked gene or to a combination of other genes. E) In cacti, there are several genes for the type of spines.

C) In rabbits and many other mammals, one genotype (ee) prevents any fur color from developing.

Mendel's second law of independent assortment has its basis in which of the following events of meiosis I? A) synapsis of homologous chromosomes B) crossing over C) alignment of tetrads at the equator D) separation of homologs at anaphase E) separation of cells at telophase

C) alignment of tetrads at the equator

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? A) incomplete dominance B) multiple alleles C) pleiotropy D) epistasis E) codominance

C) pleiotropy

Which of the following describes the ability of a single gene to have multiple phenotypic effects? A) incomplete dominance B) multiple alleles C) pleiotropy D) epistasis

C) pleiotropy

Which of the following is the best statement of the use of the addition rule of probability? A) the probability that two or more independent events will both occur B) the probability that two or more independent events will both occur in the offspring of one set of parents C) the probability that either one of two independent events will occur D) the probability of producing two or more heterozygous offspring E) the likelihood that a trait is due to two or more meiotic events

C) the probability that either one of two independent events will occur

Mendel accounted for the observation that traits that had disappeared in the F1 generation reappeared in the F2 generation by proposing that A) new mutations were frequently generated in the F2 progeny, "reinventing" traits that had been lost in the F1. B) the mechanism controlling the appearance of traits was different between the F1 and the F2 plants. C) traits can be dominant or recessive, and the recessive traits were obscured by the dominant ones in the F1. D) the traits were lost in the F1 due to dominance of the parental traits. E) members of the F1 generation had only one allele for each trait, but members of the F2 had two alleles for each trait.

C) traits can be dominant or recessive, and the recessive traits were obscured by the dominant ones in the F1.

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. 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? A) black B) brown C) yellow D) a lethal result E) white

C) yellow

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. 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? A) yyBB and yyBB B) yyBB and yyBb C) yyBb and yyBb D) yyBB and yybb E) yyBb and yybb

C) yyBb and yyBb

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? A) 1/16 B) 3/16 C) 3/8 D) 1/2 E) 9/16

D) 1/2

Skin color in a certain species of fish is inherited via a single gene with four different alleles. 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? A) 1/4 B) 1/5 C) 1/8 D) 1/2 E) 0

D) 1/2

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? A) None of the traits obeyed the law of segregation. B) The diploid number of chromosomes in the pea plants was 7. C) All of the genes controlling the traits were located on the same chromosome. D) All of the genes controlling the traits behaved as if they were on different chromosomes. E) The formation of gametes in plants occurs by mitosis only.

D) All of the genes controlling the traits behaved as if they were on different chromosomes.

Which of the following calculations require that you utilize the addition rule? A) Calculate the probability of black offspring from the cross AaBb × AaBb, when B is the symbol for black. B) Calculate the probability of children with both cystic fibrosis and polydactyly when parents are each heterozygous for both genes. C) Calculate the probability of each of four children having cystic fibrosis if the parents are both heterozygous. D) Calculate the probability of a child having either sickle-cell anemia or cystic fibrosis if parents are each heterozygous for both. E) Calculate the probability of purple flower color in a plot of 50 plants seeded from a self- fertilizing heterozygous parent plant.

D) Calculate the probability of a child having either sickle-cell anemia or cystic fibrosis if parents are each heterozygous for both.

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? A) It is recessive. B) It is dominant. C) It has a late age of onset (> 60). D) It is pleiotropic. E) It is epistatic.

D) It is pleiotropic.

Why did the F1 offspring of Mendel's classic pea cross always look like one of the two parental varieties? A) No genes interacted to produce the parental phenotype. B) Each allele affected phenotypic expression. C) The traits blended together during fertilization. D) One allele was dominant. E) Phenotype was not dependent on genotype.

D) One allele was dominant.

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. 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? A) ttRr-dwarf and pink B) ttrr-dwarf and white C) TtRr-tall and red D) TtRr-tall and pink E) TTRR-tall and red

D) TtRr-tall and pink

Mendel's observation of the segregation of alleles in gamete formation has its basis in which of the following phases of cell division? A) prophase I of meiosis B) anaphase II of meiosis C) metaphase I of meiosis D) anaphase I of meiosis E) anaphase of mitosis

D) anaphase I of meiosis

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

D) different possible assortment of chromosomes into gametes

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. A blue budgie is crossed with a white budgie. Which of the following results is not possible? A) green offspring only B) yellow offspring only C) blue offspring only D) green and yellow offspring E) a 9:3:3:1 ratio

D) green and yellow offspring

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. The flower color trait in radishes is an example of which of the following? A) a multiple allelic system B) sex linkage C) codominance D) incomplete dominance E) epistasis

D) incomplete dominance

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 be which of the following? A) red and long B) red and oval C) white and long D) purple and long E) purple and oval

D) purple and long

Two plants are crossed, resulting in offspring with a 3:1 ratio for a particular trait. What does this suggest? A) that the parents were true-breeding for contrasting traits B) that the trait shows incomplete dominance C) that a blending of traits has occurred D) that the parents were both heterozygous for a single trait E) that each offspring has the same alleles for each of two traits

D) that the parents were both heterozygous for a single trait

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? A) 1 B) 1/2 C) 1/4 D) 1/6 E) 0

E) 0

In the cross AaBbCc × AaBbCc, what is the probability of producing the genotype AABBCC? A) 1/4 B) 1/8 C) 1/16 D) 1/32 E) 1/64

E) 1/64

Drosophila (fruit flies) usually have long wings (+), but mutations in two different genes can result in bent wings (bt) or vestigial wings (vg). 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? A) 1/8 B) 3/8 C) 1/4 D) 9/16 E) 3/16

E) 3/16

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? 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

E) 9 sharp-spined:3 dull-spined:4 spineless

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. These results indicate which of the following? A) Brown is dominant to black. B) Black is dominant to brown and to yellow. C) Yellow is dominant to black. D) There is incomplete dominance. E) Epistasis is involved.

E) Epistasis is involved.

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? A) tt B) Hh C) HhTt D) T E) HT

E) HT

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? 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

E) environmental factors such as soil pH

Which of the following is an example of polygenic inheritance? A) pink flowers in snapdragons B) the ABO blood group in humans C) Huntington's disease in humans D) white and purple flower color in peas E) skin pigmentation in humans

E) skin pigmentation in humans