Chapter 14 Flashcards
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.
Why did the F1 offspring of Mendelʹs 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 phenotype was completely dominant over another.
E) Different genes interacted to produce the parental phenotype.
D) One phenotype was completely dominant over another.
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 ʺblending.ʺ
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 ʺblending.ʺ
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
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 alignments of chromosomes
E) the tendency for dominant alleles to segregate together
D) different possible alignments of chromosomes
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
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.
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
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
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%
Mendel accounted for the observation that traits which had disappeared in the F1 generation reappeared in the F2 generation by proposing that
A) new mutations were frequently generated in the F2 progeny, ʺreinventingʺ 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.
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.
Mendel was able to draw his ideas of segregation and independent assortment because of the influence of which of the following?
A) His reading and discussion of Darwinʹs Origin of Species.
B) The understanding of particulate inheritance he learned from renowned scientists of his time.
C) His discussions of heredity with his colleagues at major universities.
D) His experiments with the breeding of plants such as peas and fuchsia.
E) His reading of the scientific literature current in the field.
E) His reading of the scientific literature current in the field.
Mendelʹs 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
Mendelʹs 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
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
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
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
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
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.
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
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
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 is an example of polygenic inheritance? A) pink flowers in snapdragons B) the ABO blood group in humans C) Huntingtonʹs disease in humans D) white and purple flower color in peas E) skin pigmentation in humans
E) skin pigmentation in humans
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 provides an example of epistasis?
A) Recessive genotypes for each of two genes (aabb) results 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 (cc) 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 (cc) prevents any fur color from developing.
Most genes have many more than two alleles. However, which of the following is also true?
A) At least one allele for a gene always produces a dominant phenotype.
B) Most of the alleles will never be found in a live-born organism.
C) All of the alleles but one will produce harmful effects if homozygous.
D) There may still be only two phenotypes for the trait.
E) More than two alleles in a genotype is considered lethal.
D) There may still be only two phenotypes for the trait.
How could you best predict the maximum number of alleles for a single gene whose polypeptide product is known?
A) Search the population for all phenotypic variants of this polypeptide.
B) Count the number of amino acids in the polypeptide.
C) Mate all known genotypes and collect all possible offspring different from the parents.
D) Measure the rate of new mutations in the species and estimate the number since it first evolved.
E) Count the number of DNA nucleotides that are in the code for the polypeptides.
E) Count the number of DNA nucleotides that are in the code for the polypeptides.
