Pea plants were particularly well suited for use in Mendelʹs breeding experiments for all of the following
reasons except that
A) peas show easily observed variations in a number of characters, such as pea shape and flower color.
B) it is possible to control matings between different pea plants.
C) it is possible to obtain large numbers of progeny from any given cross.
D) peas have an unusually long generation time.
E) many of the observable characters that vary in pea plants are controlled by single genes.
What is the difference between a monohybrid cross and a 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 only
D) A monohybrid cross is performed for one generation, whereas a dihybrid cross is performed for two
E) A monohybrid cross results in a 9:3:3:1 ratio whereas a dihybrid cross gives a 3:1 ratio.
A cross between homozygous purple-flowered and homozygous white-flowered pea plants results in
offspring with purple flowers. This demonstrates
A) the blending model of genetics.
D) a dihybrid cross.
E) the mistakes made by Mendel.
The F1 offspring of Mendelʹs classic pea cross always looked like one of the two parental varieties because
A) one phenotype was completely dominant over another.
B) each allele affected phenotypic expression.
C) the traits blended together during fertilization.
D) no genes interacted to produce the parental phenotype.
E) different genes interacted to produce the parental phenotype.
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 than do dominant ones.
D) Genes are composed of DNA.
E) An organism that is homozygous for many recessive traits is at a disadvantage.
How many unique gametes could be produced through independent assortment by an individual with the
Two plants are crossed, resulting in offspring with a 3:1 ratio for a particular trait. This suggests
A) that the parents were true-breeding for contrasting traits.
B) incomplete dominance.
C) that a blending of traits has occurred.
D) that the parents were both heterozygous.
E) that each offspring has the same alleles.
Two characters that appear in a 9:3:3:1 ratio in the F2 generation should have which of the following
A) Each of the traits is controlled by single genes.
B) The genes controlling the characters obey the law of independent assortment.
C) Each of the genes controlling the characters has two alleles.
D) Four genes are involved.
E) Sixteen different phenotypes are possible.
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?
It was important that Mendel examined not just the F1 generation in his breeding experiments, but the F2
generation as well, because
A) he obtained very few F1 progeny, making statistical analysis difficult.
B) parental traits that were not observed in the F1 reappeared in the F2.
C) analysis of the F1 progeny would have allowed him to discover the law of segregation, but not the law of
D) the dominant phenotypes were visible in the F2 generation, but not in the F1.
E) many of the F1 progeny died.
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?
Which of the boxes marked 1-4 correspond to plants with dark leaves?
A) 1 only
B) 1 and 2
C) 2 and 3
D) 4 only
E) 1, 2, and 3
Which of the boxes correspond to plants with a heterozygous genotype?
B) 1 and 2
C) 1, 2, and 3
D) 2 and 3
E) 2, 3, and 4
Which of the plants will be true-breeding?
A) 1 and 4
B) 2 and 3
D) 1 only
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
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 blending of the parental traits.
E) members of the F1 generation had only one allele for each character, but members of the F2 had two
alleles for each character.
Which of the following about the law of segregation is false?
A) It states that each of two alleles for a given trait segregate into different gametes.
B) It can be explained by the segregation of homologous chromosomes during meiosis.
C) It can account for the 3:1 ratio seen in the F2 generation of Mendelʹs crosses.
D) It can be used to predict the likelihood of transmission of certain genetic diseases within families.
E) It is a method that can be used to determine the number of chromosomes in a plant.
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.
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 reading of the scientific literature current in the field
E) His experiments with the breeding of plants such as peas
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) Prophase II of meiosis
C) Metaphase I of meiosis
D) Anaphase I of meiosis
E) Anaphase of mitosis
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
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 the cross BbTt × BBtt will have black fur and long tails?
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?
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?
In a cross AaBbCc × AaBbCc, what is the probability of producing the genotype AABBCC?
Given the parents AABBCc × AabbCc, assume simple dominance and independent assortment. What proportion
of the progeny will be expected to phenotypically resemble the first parent?
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.
How many genes must be responsible for these coat colors in Labrador retrievers?
In one type cross of black × black, the results were as follows:
The genotype aabb must result in which of the following?
D) A lethal result
If true-breeding red long radishes are crossed with true breeding white oval radishes, the F 1 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
In the F2 generation of the above cross, which of the following phenotypic ratios would be expected?
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
The flower color trait in radishes is an example of which of the following?
A) A multiple allelic system
B) Sex linkage
D) Incomplete dominance
A 1:2:1 phenotypic ratio in the F2 generation of a monohybrid cross is a sign of
A) complete dominance.
B) multiple alleles.
C) incomplete dominance.
D) polygenic inheritance.
In snapdragons, heterozygotes for one of the genes have pink flowers, whereas homozygotes have red or white
flowers. When plants with red flowers are crossed with plants with white flowers, what proportion of the
offspring will have pink flowers?
Tallness (T) in snapdragons is dominant to dwarfness (t), while 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 F 1 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
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?
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
A) red × white
B) roan × roan
C) white × roan
D) red × roan
E) The answer cannot be determined from the information provided.
The relationship between genes S and N is an example of
A) incomplete dominance.
C) complete dominance.
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.
If doubly heterozygous SsNn cactuses were allowed to self-pollinate, the F2 would segregate in which of the
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
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
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
Which of the following is a possible partial genotype for the son?
Which of the following is a possible genotype for the mother?
Which of the following is a possible phenotype for the father?
A) A negative
B) O negative
C) B positive
D) AB negative
E) Impossible to determine
Which of the following is the probable genotype for the mother?
If both children are of blood group MM, which of the following 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.
E) The MN blood group is recessive to the ABO blood group.
Which describes the ability of a single gene to have multiple phenotypic effects?
A) Incomplete dominance
B) Multiple alleles
Which describes the ABO blood group system?
A) Incomplete dominance
B) Multiple alleles
Which of the following terms best describes when the phenotype of the heterozygote differs from the
phenotypes of both homozygotes?
A) Incomplete dominance
B) Multiple alleles
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
Which of the following is an example of polygenic inheritance?
A) Pink flowers in snapdragons
B) The ABO blood groups in humans
C) Huntingtonʹs disease in humans
D) White and purple flower color in peas
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) Environmental factors such as soil pH
B) The allele for blue hydrangea being completely dominant
C) The alleles being codominant
D) The fact that a mutation has occurred
E) Acknowledging that multiple alleles are involved
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.
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 lethal.
Huntingtonʹs disease is a dominant condition with late age of onset in humans. If one parent has the disease,
what is the probability that his or her child will have the disease?
A woman has six sons. The chance that her next child will be a daughter is
What is the genotype of individual II-5?
D) WW or ww
E) ww or Ww
What is the likelihood that the progeny of IV-3 and IV-4 will have wooly hair?
What is the probability that individual III-1 is Ww?
People with sickle-cell trait
A) are heterozygous for the sickle-cell allele.
B) are usually healthy.
C) have increased resistance to malaria.
D) produce normal and abnormal hemoglobin.
E) All of the above
When a disease is said to have a multifactorial basis, it means that
A) both genetic and environmental factors contribute to the disease.
B) it is caused by a gene with a large number of alleles.
C) it affects a large number of people.
D) it has many different symptoms.
E) it tends to skip a generation.
An ideal procedure for fetal testing in humans would have which of the following features?
A) Lowest risk procedure that would provide the most reliable information
B) The procedure that can test for the greatest number of traits at once
C) A procedure that provides a 3D image of the fetus
D) The procedure that can be performed at the earliest time in the pregnancy
E) A procedure that could test for the carrier status of the fetus
A scientist discovers a DNA-based test for the 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) To screen all newborns of an at-risk population
B) To design a test for identifying heterozygous carriers of the allele
C) To introduce a normal allele into deficient newborns
D) To follow the segregation of the allele during meiosis
E) To test school-age children for the disorder
An obstetrician knows that one of her patients is a pregnant woman whose fetus is at risk for a serious disorder
that is detectable biochemically in fetal cells. The obstetrician would most reasonably offer which of the
following procedures to her patient?
B) Ultrasound imaging
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) Mendelʹs law of independent assortment
B) Mendelʹs law of segregation
C) Darwinʹs explanation of natural selection
D) Darwinʹs observations of competition
E) The malarial parasite changing the allele
Cystic fibrosis (CF) is a Mendelian disorder in the human population that is inherited as a recessive. Two
normal parents have two children with CF. The probability of their next child being normal for this
characteristic is which of the following?
Phenylketonuria (PKU) is a recessive human disorder in which an individual cannot appropriately metabolize
a particular amino acid. This amino acid is not otherwise produced by humans. Therefore the most efficient
and effective treatment is which of the following?
A) Feed them the substrate that can be metabolized into this amino acid.
B) Transfuse the patients with blood from unaffected donors.
C) Regulate the diet of the affected persons to severely limit the uptake of the amino acid.
D) Feed the patients the missing enzymes in a regular cycle, i.e., twice per week.
Hutchinson-Gilford progeria is an exceedingly rare human genetic disorder in which there is very early
senility, and death, usually of coronary artery disease, at an average age of approximately 13. Patients, who
look very old even as children, do not live to reproduce. Which of the following represents the most likely
A) All cases must occur in relatives; therefore, there must be only one mutant allele.
B) Successive generations of a family will continue to have more and more cases over time.
C) The disorder may be due to mutation in a single protein-coding gene.
D) Each patient will have had at least one affected family member in a previous generation.
E) The disease is autosomal dominant.
A pedigree analysis for a given disorderʹs occurrence in a family shows that, although both parents of an
affected child are normal, each of the parents has had affected relatives with the same condition. The disorder
is then which of the following?
C) Incompletely dominant
D) Maternally inherited
E) A new mutation
One of two major forms of a human condition called neurofibromatosis (NF 1) is inherited as a dominant,
although it may be either 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.