Chapter 14 Mastering Biology
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? A) 1/8 B) 1/2 C) 1/16 D) 3/4
A) 1/8
Which of the following statements correctly explains the fact that all seven of the pea plant traits studied by Mendel obeyed the principle of independent assortment? A) All of the genes controlling the traits behaved as if they were on different chromosomes. B) All of the genes controlling the traits were located on the same chromosome. C) None of the traits obeyed the law of segregation. D) The diploid number of chromosomes in the pea plants was seven.
A) All of the genes controlling the traits behaved as if they were on different chromosomes.
A gene for the MN blood group has codominant alleles M and N. If both children in a family are of blood type M, which of the following situations is possible? A) Each parent is either M or MN. B) Each parent must be type M. C) Both children are heterozygous for this gene. D) Neither parent can have the N allele.
A) Each parent is either M or MN.
Which of the following statements about independent assortment or segregation is correct? A) The law of independent assortment describes the behavior of two or more genes relative to one another. B) The law of segregation describes the behavior of two or more genes relative to one another. C) The law of independent assortment is accounted for by observations of prophase I of meiosis. D) The law of segregation is accounted for by anaphase of mitosis.
A) The law of independent assortment describes the behavior of two or more genes relative to one another.
Which of the following statements correctly describes how Mendel accounted for the observation that traits had disappeared in the F1 generation and then reappeared in the F2 generation? A) Traits can be dominant or recessive, and the recessive traits were "hidden" by the dominant ones in the F1. B) New mutations were frequently generated in the F2 progeny, causing traits that had been lost in the F1 to reappear in the F2. C) Members of the F1 generation had only one allele for each trait, but members of the F2 had two alleles for each trait. D) The mechanism controlling the appearance of traits was different between the F1 and the F2 plants.
A) Traits can be dominant or recessive, and the recessive traits were "hidden" by the dominant ones in the F1.
In cattle, roan coat color (mixed red and white hairs) occurs in the heterozygous (CRCW) offspring of red (CRCR) and white (CWCW) homozygotes. Which of the following crosses would produce offspring in the ratio of 1 red:2 roan:1 white? A) roan × roan B) white × roan C) red × white D) red × roan
A) roan × roan
Which of the following phenotypes is an example of polygenic inheritance? A) skin pigmentation in humans B) white and purple flower color in peas C) pink flowers in snapdragons D) the ABO blood group in humans
A) skin pigmentation in humans
Which of the following statements best describes the addition rule of probability? A) the probability that either one of two independent events will occur B) the probability of producing two or more heterozygous offspring C) the probability that two or more independent events will occur simultaneously D) the likelihood that a trait is due to two or more meiotic events
A) the probability that either one of two independent events will occur
In pea plants, the tall phenotype is dominant to the dwarf phenotype. If a heterozygous pea plant is crossed with a homozygous tall pea plant, what is the probability that the offspring will be dwarf in size? A) 1/2 B) 0 C) 1/4 D) 1
B) 0
Two organisms with genotype AaBbCcDdEE mate. These loci are all independent. What fraction of the offspring will have the same genotype as the parents? A) 4/3 B) 1/16 C) 9/64 D) 3/4
B) 1/16 ~Breaking the question down into individual loci makes it simpler. The offspring of Aa ×Aa will be Aa 50% (one-half) of the time. The same is true for Bb, Cc, and Dd. Two EE individuals can only have EE offspring, so that probability is 1. The chance of an offspring being identical to the parent is therefore (1/2)4, or 1/16.~
The pattern of inheritance can be predicted from data if one is given the parent or offspring genotypes or phenotypes. Two organisms, with genotypes BbDD and BBDd, are mated. Assuming independent assortment of the B/b and D/d genes, determine the genotypic ratios in offspring that would occur. A) 9/16 BBDD, 3/16 BbDD, 3/16 BBDd, 1/16 bbdd B) 1/4 BBDD, 1/4 BbDD, 1/4 BBDd, 1/4 BbDd C) 1/4 BBDD, 1/2 BbDd, 1/4 bbdd D) 1/2 BBDD, 1/2 bbdd
B) 1/4 BBDD, 1/4 BbDD, 1/4 BBDd, 1/4 BbDd
Which of the following scenarios describes an example of epistasis? A) In Drosophila (fruit flies), white eyes can be due to an X-linked gene or to a combination of other genes. B) In rabbits and many other mammals, one genotype (ee) prevents any fur color from developing. C) In cacti, there are several genes for the type of spines. D) 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.
What was the most significant conclusion that Gregor Mendel drew from his experiments with pea plants? A) Genes are composed of DNA. 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) There is considerable genetic variation in garden peas
B) Traits are inherited in discrete units and are not the result of "blending."
Height in humans generally shows a normal (bell-shaped) distribution. What type of inheritance most likely determines height? A) a combination of epistasis and environmental factors B) a combination of polygenic inheritance and environmental factors C) a combination of complete dominance and environmental factors D) incomplete dominance
B) a combination of polygenic inheritance and environmental factors
What is an allele? A) a type of chromosome B) an alternative version of a gene C) a variety of pea plant used by Mendel D) the dominant form of a gene
B) an alternative version of a gene ~A diploid organism carries two alleles for each autosomal gene. The two alleles are found at comparable locations (loci) on homologous chromosomes. The alleles may be identical or slightly different, but they affect the same genetic character.~
The individual with genotype AaBbCCDdEE can make many kinds of gametes. Which of the following correctly describes why this situation is possible? A) recurrent mutations form new alleles B) different possible assortment of chromosomes into gametes occurs C) crossing over during prophase I leads to genetic variety D) there is a tendency for dominant alleles to segregate together
B) different possible assortment of chromosomes into gametes occurs
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 flower color trait in radishes is an example of which of the following inheritance patterns? A) a multiple allelic system B) incomplete dominance C) sex linkage D) codominance
B) incomplete dominance
A man has extra digits (six fingers on each hand and six toes on each foot). His wife and their daughter have the normal number of digits (five fingers on each hand and five toes on each foot.) Having extra digits is a dominant trait. The couple's second child has extra digits. What is the probability that their next (third) child will have extra digits? A) 1/16 B) 3/4 C) 1/2 D) 1/8
C) 1/2
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. What is the most probable genotype of each parent? A) GG × gg B) gg × Gg C) Gg × Gg D) GgG × Gg
C) Gg × Gg
Which of the following is true about a plant with the genotype AABbcc? A) It is triploid. B) It will not express the recessive c allele. C) It is homozygous at two loci. D)It is heterozygous at two loci.
C) It is homozygous at two loci. ~An organism having a pair of identical alleles at a given locus is said to be homozygous for that locus. Here, the plant is homozygous at loci A and C.~
In his breeding experiments, Mendel first crossed true-breeding plants to produce a second generation, which were then allowed to self-pollinate to generate the offspring. How do we name these three generations? A) F ... P₁ ... P₂ B) P₁ ... P₂ ... P₃ C) P ... F₁ ... F₂ D) F₁ ... F₂ ... F₃
C) P...F₁...F₂ ~Mendel started with true-breeding P generation plants, and in a typical experiment generated two subsequent generations, called F₁ and F₂.~
You cross a true-breeding red-flowered snapdragon with a true-breeding white-flowered one. All of the F1 are pink. What does this say about the parental traits? A) Red is completely dominant. B) Both red and white are pleiotropic. C) Red shows incomplete dominance over white.
C) Red shows incomplete dominance over white. ~Red shows incomplete dominance over white, and the F1 is therefore pink.~
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 ________. A) 25% sharp-spined, 50% dull-spined, 25% spineless progeny B) 50% sharp-spined, 50% dull-spined progeny C) all sharp-spined progeny D) It is impossible to determine the phenotypes of the progeny.
C) all sharp-spined progeny
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 cacti have spines. Homozygous recessive nn cacti have no spines at all. The relationship between genes S and N is an example of which of the following inheritance patterns? A) pleiotropy B) incomplete dominance C) epistasis D) codominance
C) epistasis
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) 3/8 B) 1/16 C) 9/16 D) 1/2
D) 1/2
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? A) 1/2 B) 1 C) 0 D) 1/4
D) 1/4
Suppose two individuals with the genotype AaBbCc are mated. Assuming that the genes are not linked, what fraction of the offspring are expected to be homozygous recessive for the three traits? A) 1/8 B) 1/4 C) 1/16 D) 1/64
D) 1/64
What is the probability of producing the genotype AABBCC in a cross of individuals who both possess this genotype: AaBbCc? A) 1/4 B) 1/16 C) 1/8 D) 1/64
D) 1/64
Which of the following statements is correct in describing the terms monohybrid cross and dihybrid cross? A) A monohybrid cross is performed for one generation, whereas a dihybrid cross is performed for two generations. B) A monohybrid cross results in a 9:3:3:1 ratio, whereas a dihybrid cross gives a 3:1 ratio. C) A monohybrid cross involves a single parent, whereas a dihybrid cross involves two parents. D) 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 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.
A black guinea pig crossed with a guinea pig with albinism produced 12 black offspring. When the albino was crossed with a second black animal, six blacks and six albinos were obtained. What is the best explanation for this genetic situation? A) Albinism and black are codominant. B) Albinism is a recessive trait; black is codominant. C) Albinism is a dominant trait; black is incompletely dominant. D) Albinism is a recessive trait; black is a dominant trait.
D) Albinism is a recessive trait; black is a dominant trait.
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) T B) HhTt C) Hh D) HT
D) HT
Folk singer Woody Guthrie died of Huntington's disease, an autosomal dominant disorder. Which statement below must be true? A) All of his children will develop Huntington's disease. B) His sons will develop Huntington's disease but not his daughters. C) His daughters will die of Huntington's disease but not his sons. D) It is very likely that at least one of Woody Guthrie's parents also had the allele for Huntington's disease.
D) It is very likely that at least one of Woody Guthrie's parents also had the allele for Huntington's disease. ~Unless the disease is caused by a new mutation, which is quite rare, individuals with a dominant condition must have inherited the dominant allele from one of their parents. As it happens, Guthrie's mother also died of Huntington's disease.~
Why did all of the F1 offspring of Mendel's classic pea cross always look like one of the two parental varieties? A) Each allele affected phenotypic expression. B) No genes interacted to produce the parental phenotype. C) The traits blended together during fertilization. D) One allele was dominant.
D) One allele was dominant
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? A) purple and oval B) white and long C) red and long D) purple and long
D) purple and long