Biology: A Guide to the Natural World, 5e (Krogh)
Chapter 11 The First Geneticist: Mendel and His Discoveries
1) Which of the following was not one of Mendel’s main inferences from his research?
A) The basic units of genetics are material elements.
B) The genetic material elements come in pairs.
C) Genes are lengths of DNA.
D) The genetic material elements can retain their character through many generations.
E) The genetic material elements separate during the formation of gametes.
2) What is the term for an observable trait of an organism?
A) element
B) phenotype
C) hybrid
D) genotype
E) allele
3) The seeds in a pod of one of Mendel’s pea plants are:
A) produced only when a plant is cross-fertilized.
B) genetically identical to each other but different from other peas in other pods.
C) produced only when a plant is self-fertilized.
D) each the result of a separate fertilization event.
E) genetically identical to each other and all other peas from that plant.
4) Mendel postulated that individuals have genetic elements that exist in pairs, which determine
a single phenotype. What do we now know these pairs of elements to be?
A) two haploid sets of chromosomes
B) two alleles of a gene on homologous chromosomes
C) pairs of sister chromatids
D) pairs of centromeres
E) a sperm and an egg
5) Mendel wanted to make sure his starting plants bred true, meaning the:
A) seeds would always sprout.
B) peas would always be green.
C) phenotypes of the offspring in each generation could not be predictable.
D) phenotypes of the offspring in each generation were always the same as the parent.
E) phenotypes of the offspring in each generation would sometimes look like the male parent and
sometimes look like the female parent.
6) The D gene controls pea plant height. The DD and dd genotypes confer tall and dwarf
phenotypes, respectively. What is the relationship between D and d?
A) They are two different plant chromosomes.
B) They are two different genes on the same chromosome.
C) They are alleles of the same gene.
D) They are two possible homozygous genotypes.
E) They are two possible heterozygous genotypes.
7) Before Mendel, people had observed inheritance of dominant and recessive traits by following
many generations of plants and animals. What was different about Mendel’s work?
A) He used a plant that had never been cultivated before.
B) He kept careful count of his results, including mathematical analysis.
C) His results were immediately accepted and applied to other studies.
D) He followed more generations than anyone else.
E) He did both cross- and self-fertilizations.
8) Mendel crossed true-breeding pea plants and found the dominant trait always appeared in the
F1 generation, but it appeared in a ________ ratio of dominant to recessive in the F2 generation.
A) 1:3
B) 1:2
C) 3:1
D) 1:1
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9) A and a are dominant and recessive alleles, respectively, of the same gene. Which genotype(s)
would result in an individual with the dominant phenotype?
A) AA and aa
B) Aa and aa
C) only AA
D) AA and Aa
E) only Aa
10) A and a are dominant and recessive alleles, respectively, of the same gene. Which
genotype(s) would result in an individual with the recessive phenotype?
A) Aa and aa
B) AA and aa
C) Aa only
D) AA only
E) aa only
11) Cystic fibrosis (CF) is caused by a recessive allele. A child has CF, even though neither of
his parents has CF. Which of the following describes the genotypes of the parents?
A) One is homozygous dominant for the CF gene, and the other is heterozygous.
B) One is homozygous recessive for the CF gene, and the other is heterozygous.
C) They are both homozygous recessive for the CF gene.
D) They are both homozygous dominant for the CF gene.
E) They are both heterozygous for the CF gene.
12) Cystic fibrosis (CF) is caused by a recessive allele. A child has CF, even though neither of
his parents has CF. This couple also has a child who does not have CF. What is the probability
the unaffected child is heterozygous?
A) 2/3
B) 1/3
C) 1/2
D) 3/4
E) 1/4
13) When a yellow-seeded pea plant with the genotype Yy produces gametes, what will be the
genotype(s) of the gametes?
A) All will be YY.
B) All will be Yy.
C) They will be either all Y or all y.
D) Half will be YY, and half will be yy.
E) Half will be Y, and half will be y.
14) In Mendel’s pea plant experiments, in order for him to have observed a 3:1 phenotypic ratio
in the F2 generation, which of the following must be true?
A) The two alleles of a pair separate in gamete formation.
B) The pairs of alleles must be either homozygous dominant or homozygous recessive.
C) Both alleles of a pair must go into each gamete together.
D) Both of the F1 parents must be breed true.
15) The genotype Ff is an example of a:
A) trait controlled by multiple genes.
B) homozygous genotype.
C) monohybrid genotype.
D) heterozygous genotype.
E) dihybrid genotype.
16) Widow’s-peak hairline in humans is dominant to non-widow’s-peak hairline. If a person has a
widow’s-peak hairline, what is his or her genotype?
A) The genotype must be homozygous recessive.
B) The genotype is either homozygous dominant or homozygous recessive.
C) The genotype must be heterozygous.
D) The genotype is either heterozygous or homozygous dominant.
E) The genotype must be homozygous dominant.
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17) The Law of Segregation states that:
A) gene pairs assort independently of each other during gamete formation.
B) differing characters in organisms result from two alleles that separate in gamete formation,
such that each gamete gets only one of the two alleles.
C) differing characters are the result of either the homozygous dominant or the homozygous
recessive condition.
D) phenotypes are always determined by genotypes.
E) one allele of a pair must always be dominant and the other must always be recessive.
18) If an individual exhibits a recessive trait, which of the following statements can you be sure
of?
A) The phenotype for this trait is different from the phenotype of the homozygous dominant
genotype for this trait.
B) The genotype of this trait will be heterozygous.
C) Both parents of this individual had the same genotype for this trait.
D) Any siblings of this individual will have the same phenotype for this trait.
E) Any children this individual has will always exhibit the trait, regardless of the genotype of the
other parent.
19) Dimpled cheeks are dominant to undimpled cheeks. If there exists a 50 percent chance that a
child will have dimpled cheeks, the parental genotypes must be:
A) dd and dd.
B) Dd and dd.
C) DD and Dd.
D) Dd and Dd.
E) DD and dd.
20) When two identical alleles for a character are present, the genotype is referred to as:
A) heterozygous.
B) homozygous.
C) dominant.
D) recessive.
21) In Mendel’s pea plants, yellow seeds are dominant to green seeds. If a true-breeding green-
seed-producing plant is crossed to a heterozygous yellow-seed-producing plant, what percentage
of offspring produces green seeds?
A) 10 percent
B) 50 percent
C) 33 percent
D) 25 percent
E) 100 percent
22) In humans, “unattached” earlobes are dominant over “attached” earlobes. Widow’s-peak
hairline is dominant over non-widow’s-peak hairline. Use E and e for the earlobe phenotype
alleles and W and w for the hairline phenotype alleles. A woman and a man, both with genotype
EeWw, have a child. What is the probability that the child will have attached earlobes and a
widow’s peak?
A) 1/16
B) 9/16
C) 1/3
D) 3/4
E) 3/16
23) Which of the following represents a dihybrid cross?
A) YYyy x PPpp
B) YY x pp
C) YyPp x YyPp
D) YP x Yp
E) Yp x YY
24) In humans, “unattached” earlobes are dominant over “attached” earlobes. Widow’s-peak
hairline is dominant over non-widow’s-peak hairline. Use E and e for the earlobe phenotype
alleles and W and w for the hairline phenotype alleles. A woman with unattached earlobes and a
widow’s peak and a man with attached earlobes and a widow’s peak have a child. The child has
attached earlobes and a non-widow’s-peak hairline. What are the genotypes of the parents?
A) EEWW and eeww
B) EeWw and eeWw
C) EEWW and eeWw
D) EeWw and EeWW
E) EeWw and eeww
25) What is the physical basis for the independent assortment observation that Mendel made?
A) Male and female gametes are produced in separate organs in separate individuals.
B) Sister chromatids do not separate until meiosis II.
C) There are two chromosome divisions in meiosis.
D) Homologous chromosomes are randomly aligned and separated during meiosis.
E) Recombination (crossing over) occurs in meiosis.
26) The Law of Independent Assortment states that:
A) in meiosis, crossing over creates genetically diverse gametes.
B) in fertilization, the combining of sperm and eggs is random.
C) generation of male and female gametes must occur in separate organisms.
D) in any dihybrid cross, it is possible to get any combination of phenotypes.
E) in gamete formation, gene pairs are transmitted independently of each other.
27) When Mendel crossed plants and followed two traits (a dihybrid cross), he saw a 9:3:3:1
ratio of traits in the F2 generation. What did he conclude?
A) The two traits affect each other’s transmission.
B) Dominant traits are always more common than recessive ones.
C) In meiosis, one allele of each gene is passed to each gamete.
D) The transmission of one trait is unaffected by the other.
28) Let S = smooth pea and s = wrinkled pea; Y = yellow pea and y = green pea. What are the
different possible genotypes of the gametes produced by a plant that is heterozygous for both
characters?
A) All will be SsYy.
B) Ss, Yy
C) S, s, Y, y
D) SY, Sy, sY, sy
E) SY, sy
29) Let S = smooth pea and s = wrinkled pea; Y = yellow pea and y = green pea. What pea
phenotype would be produced by the genotype SsYy?
A) smooth, yellow
B) smooth, green
C) wrinkled, yellow
D) wrinkled, green
30) In order to track the inheritance of a single character, you would need to do a:
A) monohybrid cross.
B) dihybrid cross.
C) trihybrid cross.
D) true-breeding cross.
31) In order to track the inheritance of two characters, you would need to do a:
A) monohybrid cross.
B) dihybrid cross.
C) trihybrid cross.
D) true-breeding cross.
32) In humans, freckles are dominant to no freckles, and unattached earlobes are dominant to
attached earlobes. Two individuals who both have freckles and unattached earlobes have a child
with no freckles and attached earlobes. What are the genotypes of the parents? (F = freckles; E =
unattached earlobes)
A) FFEE x ffee
B) Ffee x FFEE
C) FfEe x FfEe
D) FFEE x FFEe
E) ffee x ffee
33) In Mendel’s pea plants, yellow seeds are dominant to green seeds. Purple flowers are
dominant to white flowers. Use Y and y for the seed color alleles and P and p for the flower color
alleles. Flower color and seed color assort independently. A plant of unknown genotype with
yellow seeds and purple flowers is crossed to a plant with green seeds and white flowers. The
offspring all have yellow seeds, but some have purple flowers, and some have white flowers.
What is the genotype of the yellow-seeded, purple-flowered plant?
A) YyPp
B) YYPp
C) YyPP
D) YYPP
E) Yypp
34) In Mendel’s pea plants, yellow seeds are dominant to green seeds. Purple flowers are
dominant to white flowers. Use Y and y for the seed color alleles and P and p for the flower color
alleles. Flower color and seed color assort independently. A true-breeding plant with green seeds
and white flowers is crossed to a plant that is heterozygous for the genes for both phenotypes.
What is the probability that the cross will yield a plant with green seeds and white flowers?
A) 3/16
B) 3/32
C) 1/32
D) 1/16
E) 1/4
35) In Mendel’s pea plants, yellow seeds are dominant to green seeds. Purple flowers are
dominant to white flowers. Use Y and y for the seed color alleles and P and p for the flower color
alleles. Flower color and seed color assort independently. If a plant that is heterozygous for both
flower color and seed color genes is self-fertilized, what proportion of the offspring will have
one of the dominant phenotypes, either the seed color or flower color, but not both?
A) 6/64
B) 6/32
C) 6/16
D) 9/32
E) 9/16
36) When Mendel crossed heterozygotes for flower color and seed color, what proportion of the
offspring had both dominant phenotypes?
A) 3/4
B) 3/16
C) 1/3
D) 1/16
E) 9/16
37) In Mendel’s pea plants, yellow seeds are dominant to green seeds. Purple flowers are
dominant to white flowers. Use Y and y for the seed color alleles and P and p for the flower color
alleles. Flower color and seed color assort independently. What is the relationship between the Y
and P?
A) They are two different genes on two different chromosomes.
B) They are two different genes on the same chromosome.
C) They are two different chromosomes in the pea plant.
D) They are the pleiotropic effects of a single gene.
E) They are incompletely dominant alleles of the same gene.
38) Mendel’s work was presented in ________ but not recognized and rediscovered until
________.
A) 1825; 1950
B) 1865; 1900
C) 1850; 1900
D) 1800; 1900
E) 1890; 1920
39) Crossing two pink snapdragons yields some seeds that produce red-flowering plants, some
seeds that produce white-flowering plants and some seeds that produce pink-flowering plants. If
this trait operates by incomplete dominance and the allele R represents red flowers and the allele
r represents white flowers, what genotype would a plant with pink flowers have for this trait?
A) RR
B) Rr
C) rr
D) RrRr
40) What is the basis for incomplete dominance?
A) Both alleles of a gene produce weakly functioning proteins.
B) One allele produces some functioning protein; the other allele is nonfunctional.
C) Crossing over has switched alleles for a gene on homologous chromosomes.
D) One gene has many effects.
E) An individual has more than two alleles for a gene.
41) A plant that produces white flowers is crossed to a plant that produces orange flowers. All
the offspring produced pale orange flowers. What can you conclude?
A) Pale orange flower is the dominant phenotype.
B) This trait shows incomplete dominance.
C) Orange flower is the dominant phenotype.
D) The genes for flower color do not assort independently.
E) White flower is the dominant phenotype.
42) If all of Mendel’s monohybrid crosses had involved traits that function by incomplete
dominance, would his results have supported blending inheritance?
A) It cannot be determined with the information given.
B) Yes; a cross between red and white flowers would yield all pink offspring.
C) No; he would still have seen the dominant and recessive traits reappear in the F2 generation.
D) Yes; there is always a wide range of phenotypes in monohybrid crosses.
43) Crossing a true-breeding red-flowered snapdragon with a true-breeding white-flowered
snapdragon produces all pink snapdragons in the F1 generation. If F1 individuals are crossed,
what will be the ratio of phenotypes in the F2 generation?
A) 1 red:1 pink: 2 white
B) 2 red:1 pink: 2 white
C) 1 red: 2 pink: 1 white
D) 3 pink: 1 white
E) 3 white: 1 pink
44) A person with the genotype IAIB has type AB blood. This is an example of:
A) the effect of the environment on phenotype.
B) dihybridness.
C) monohybridness.
D) codominance.
E) incomplete dominance.
45) What is the basis of codominance?
A) There is only one allele for a gene.
B) One allele of a gene encodes a protein, and the other allele is nonfunctional.
C) One gene has many alleles.
D) Each allele of a gene produces a protein that functions to create a trait.
E) One allele can have many effects on a phenotype.
46) Which type of inheritance is most likely to display a bell curve of phenotypes?
A) codominance
B) multiple alleles
C) polygenic inheritance
D) monohybrid cross
E) incomplete dominance
47) What is the significance of multiple alleles?
A) They make it possible for one person to have more than two alleles for a gene.
B) They are the reason one gene can affect more than one character.
C) They are the reason the environment can affect characters.
D) They allow for a range of traits in the population.
48) A, B, and O blood type in humans is controlled by a single gene with three alleles: IA, IB,
and i. Type O is the recessive trait. The i allele is recessive to both IA and IB. Which of the
following could be possible genotypes of the parents of a person with type O blood?
A) IAIB and ii
B) IAi and IAIA
C) IAi and IBi
D) IAIB and IAIB
49) Height is an example a character that displays continuous variation in humans. What is the
reason for the range of heights in humans?
A) There is incomplete dominance of the tall allele over the short allele.
B) There are multiple alleles for the height gene.
C) Most traits such as height are governed by the interaction of many genes.
D) There is only one gene for height in humans, but the environment can influence the
expression of the gene.
50) Characters such as height, weight, and skin color are controlled by many genes acting
together. These are examples of:
A) multiple alleles.
B) codominance.
C) incomplete dominance.
D) polygenic inheritance.
51) The phenotype of an organism can be influenced by:
A) its genotype.
B) its environment.
C) both its environment and its genotype.
D) neither its genotype nor its environment.
52) Mendel’s contribution to genetics was the discovery of DNA.
53) Mendel’s crosses with pea plants disproved the notion that, when individuals with two
different traits are mated, the genetic information blends in the offspring and is not retained as
separate elements.
54) If a person has a recessive trait, the genotype must be homozygous recessive for the trait.
55) When two individuals with different traits are crossed, either the dominant or the recessive
trait, and not an intermediate trait, is always seen, no matter what the organism or phenotype.
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Match the following.
A) Alleles come in dominant and recessive forms.
B) There is no “blending” in inheritance.
C) Neither allele is completely dominant over the other.
D) Genes assort independently in gamete formation.
56) When true-breeding P plants of different types are crossed, the offspring do not have a
phenotype intermediate between the two parents.
Topic: Section 11.3
Skill: Knowledge/Comprehension
57) When true-breeding P plants are crossed, all offspring have the trait of one of the parents.
Topic: Section 11.4
Skill: Knowledge/Comprehension
58) When two traits are followed in a dihybrid cross, heterozygotes in the F1 generation produce
offspring with all combinations of phenotypes, in a 9:3:3:1 ratio.
Topic: Section 11.5
Skill: Knowledge/Comprehension
59) The crossing of two true-breeding parents seems to produce a blending in the F1 generation,
but the dominant and recessive traits are expressed again in the F2 generation.
Topic: Section 11.7
Skill: Knowledge/Comprehension
60) The physical characteristics of an organism, or its ________, are determined by its genetic
makeup, referred to as its ________.
61) A particular quality of an organism is referred to as a ________, each variation of which is a
particular ________.
62) In the Law of ________, Mendel stated that two genetic elements are separated in gamete
formation.
63) If a plant heterozygous for the genes for both seed color and shape is self-fertilized, the ratio
of offspring with smooth, green seeds is ________/16. (Yellow and smooth are the dominant
phenotypes.)
64) A true-breeding strain of red tulips is crossed to a true-breeding strain of white tulips. All the
offspring have pink flowers. When a pink-flowered plant is self-fertilized, the offspring have red,
pink, and white flowers, in the ratio 1:2:1. This type of inheritance is an example of ________.
65) List two characteristics of the garden pea plant, Pisum sativum, that make it an ideal
organism for genetic experiments.
66) In a breeding experiment with yellow and green true-breeding parents, Mendel took yellow
seeds from his F2 generation, planted them, and self-pollinated the flowers to produce an F3
generation. He saw that some produced all yellow seeds, and some produced a mix of yellow and
green seeds. How can these results be explained?
67) Cystic fibrosis (CF) is a disease caused by a recessive allele, and the disease appears only in
the homozygous recessive genotype. Two parents do not have cystic fibrosis, but they produce a
child with this disorder. Fully explain what has occurred, using the appropriate terminology and
diagram (you must provide this diagram).
68) If an individual has genotype AaBb, how many different gametes can he or she produce?
What combinations of alleles are possible?
69) What is the difference between a monohybrid and a dihybrid cross?
70) When Mendel performed a dihybrid cross of plants heterozygous for seed color and seed
shape, he saw a 9:3:3:1 ratio in the next generation. Explain what this ratio describes and what
each number represents.
71) Consider the following information for a dihybrid cross. The dominant allele F codes for
freckles, whereas the recessive allele f codes for no freckles. The dominant allele E codes for
long eyelashes, whereas the recessive allele e codes for short eyelashes. Both parents have the
genotypes of ee and Ff. Indicate the following: (1) the phenotype of both parents, (2) the possible
gametes that each parent can make, (3) all of the possible phenotypes for the offspring, and (4)
the phenotypic ratio obtained after the Punnett square is drawn.
72) The inheritance of curly hair illustrates incomplete dominance. When a curly haired
individual reproduces with a straight-haired one, the children all have wavy hair. What offspring
would be produced, in what proportions, when two people with wavy hair reproduce?
73) A man with type O blood has a sister with type AB blood. What are the genotypes and
phenotypes of their parents?
74) Hydrangeas can have either pink or blue flowers. You want to test if the flower color is
influenced by the environment, such as the acidity of the soil. Design an experiment to test if soil
acidity affects flower color.
75) Identical twins are genetically the same but do not always look or act exactly alike. Propose a
hypothesis to explain this.
Refer to the figure below, and then answer the question that follows.
76) In his basic experiments, Mendel began with true-breeding parental (P) plants. What results
did he see when he cross-fertilized P generation plants that had different traits?
A) The F1 plants had new traits that were a blend of P traits.
B) All F1 plants had the trait of one or the other P plant.
C) The F1 plants had an entirely new trait, not seen in either P plant.
D) The F1 plants showed a combination of the two P traits in a 1:1 ratio.
E) The F1 plants showed a combination of the two P traits, in a 3:1 ratio.
Refer to the figure below, and then answer the question that follows.
77) In a dihybrid cross, if heterozygotes are crossed, what fraction of the offspring is expected to
have both the dominant phenotypes?
A) 1/16
B) 1/3
C) 2/3
D) 3/16
E) 9/16