Quiz 6

Question 1

Which of the following is a true statement about sexual versus asexual reproduction?

a) Asexual reproduction, but not sexual reproduction, is characteristic of plants and fungi.
b) In sexual reproduction, individuals transmit copies of 50% of their genes to each of their offspring.
c) In asexual reproduction, offspring are produced by fertilization without meiosis.
d) Sexual reproduction requires that parents be diploid.

Answer 1

b) In sexual reproduction, individuals transmit copies of 50% of their genes to each of their offspring.

Question 2

The karyotype of one species of primate has 48 chromosomes. In a particular female, cell division goes awry and she produces one of her eggs with an extra chromosome (25). The most probably source of this error would be a mistake in which of the following?

a) mitosis in her ovary
b) metaphase I of one meiotic event
c) telophase I of one meiotic event
d) either anaphase I or II

Answer 2

d) either anaphase I or II

Question 3

How does the sexual life cycle increase the genetic variation in a species?

a) by allowing crossing over
b) by allowing fertilization
c) through independent assortment
d) by decreasing mutation frequency

Answer 3

a) by allowing crossing over

Question 4

Independent assortment of chromosomes is a result of

a) the random and independent way in which each pair of homologous chromosomes lines up at the metaphase plate during meiosis I.
b) the random nature of the fertilization of ova by sperm.
c) the random distribution of the sister chromatids to the two daughter cells during anaphase II.
d) the random and independent way in which each pair of homologous chromosomes lines up at the metaphase plate during meiosis I, the random nature of the fertilization of ova by sperm, and the random distribution of the sister chromatids to the two daughter cells during anaphase II.

Answer 4

a) the random and independent way in which each pair of homologous chromosomes lines up at the metaphase plate during meiosis I.

Remember:
- Independent assortment in meiosis takes place in eukaryotes during metaphase I of meiotic division.. MEOSIS I

Question 5

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. Which of the following statements about this cactus is TRUE?

a) A plant with the genotype ssnn has dull spines.
b) A plant with the genotype SsNn has sharp spines.
c) The relationship between spine presence and sharpness is an example of multiple alleles at a single locus.
d) The alleles for spine sharpness are codominant.

Answer 5

b) A plant with the genotype SsNn has sharp spines.

Question 6

Sketch a pedigree that represents the following family history for the dominant trait W, then answer the question that follows.

A homozygous recessive male (ww) mates with a heterozygous female (Ww), who is affected by the trait. They have 6 children: two affected sons, one affected daughter, three unaffected sons, and one unaffected daughter.

One affected son mates with an unaffected female and they have one affected son.

The other affected son mates with an unaffected female and they have one affected son, one unaffected son, and one unaffected daughter. If this daughter mates with an affected male, what are the chances that a child born to them will be affected?

a) 0%
b) 25%
c) 50%
d) 100%

Answer 6

c) 50%

Question 7

Meiosis II is similar to mitosis in that..?

a) sister chromatids separate during anaphase
b) DNA replicates before the division
c) the daughter cells are diploid
d) homologous chromosomes synapse

Answer 7

a) sister chromatids separate during anaphase

Question 8

If the DNA content of a diploid cell in the G1 phase of the cell cycle is x, then the DNA content of the same cell at metaphase of meiosis I would be:

a) 0.25x
b) 0.5x
c) x
d) 2x

Answer 8

d) 2x

Question 9

If we continued to following the cell linage from the previous question, then the DNA content of a single cell at metaphase of meiosis II would be:

a) 0.25x
b) 0.5x
c) x
d) 2x

Answer 9

c) x

Question 10

A human cell containing 22 autosomes and a Y chromosome is:

a) a sperm
b) an egg
c) a zygote
d) a somatic cell of a male

Answer 10

a) a sperm

Question 11

Homologous chromosomes move towards opposite poles of a dividing cell during:

a) mitosis
b) meiosis I
c) meiosis II
d) fertilization

Answer 11

b) meiosis I

Question 12

In sexual reproduction, the reduction division stage is known as

a) fertilization.
b) meiosis I
c) G1.
d) meiosis II.
e) anaphase.

Answer 12

b) meiosis I

Question 13

Which of the following might result in a human zygote with 45 chromosomes?

a) an error in the alignment of chromosomes on the metaphase plate
b) fertilization of a 23-chromosome human egg by a 22-chromosome sperm of a closely related species
c) an error in either egg or sperm meiotic anaphase
d) failure of the egg nucleus to be fertilized by the sperm
e) lack of chiasmata in prophase I

Answer 13

c) an error in either egg or sperm meiotic anaphase

Question 14

The human X and Y chromosomes

a) include only genes that govern sex determination.
b) are almost entirely homologous, despite their different names.
c) are both present in every somatic cell of males and females alike.
d) are of approximately equal size and number of genes.
e) include genes that determine an individual’s sex.

Answer 14

e) include genes that determine an individual’s sex.

Question 15

Which of the following happens at the conclusion of meiosis I?

a) Sister chromatids are separated.
b) The chromosome number per cell is conserved.
c) The sperm cells elongate to form a head and a tail end.
d) Four daughter cells are formed.
e) Homologous chromosomes are separated.

Answer 15

e) Homologous chromosomes are separated.

Question 16

Independent assortment of chromosomes is a result of

a) the random nature of the fertilization of ova by sperm.
b) the random and independent way in which each pair of homologous chromosomes lines up at the metaphase plate during meiosis I, the random nature of the fertilization of ova by sperm, the random distribution of the sister chromatids to the two daughter cells during anaphase II, and the relatively small degree of homology shared by the X and Y chromosomes.
c) the relatively small degree of homology shared by the X and Y chromosomes.
d) the random and independent way in which each pair of homologous chromosomes lines up at the metaphase plate during meiosis I.
e) the random distribution of the sister chromatids to the two daughter cells during anaphase II.

Answer 16

d) the random and independent way in which each pair of homologous chromosomes lines up at the metaphase plate during meiosis I.

Question 17

For a species with a haploid number of 23 chromosomes, how many different combinations of maternal and paternal chromosomes are possible for the gametes?

a) 920
b) 46
c) 460
d) 23
e) about 8 million

Answer 17

e) about 8 million

Question 18

During which stage(s) of meiosis do centromeres of sister chromatids disjoin and chromatids separate?

a) Anaphase I
b) Anaphase II
c) Anaphase I and Anaphase II
d) Metaphase I and Metaphase II
e) Prophase I and Prophase II

Answer 18

b) Anaphase II

Question 19

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) Black is dominant to brown and to yellow.
b) Epistasis is involved.
c) Brown is dominant to black.
d) Yellow is dominant to black.
e) There is incomplete dominance.

Answer 19

b) Epistasis is involved.

Question 20

Mendel accounted for the observation that traits which had disappeared in the F1 generation reappeared in the F2 generation by proposing that

a) members of the F1 generation had only one allele for each trait, but members of the F2 had two alleles for each trait.
b) new mutations were frequently generated in the F2 progeny, “reinventing” traits that had been lost in the F1.
c) the traits were lost in the F1 due to dominance of the parental traits.
d) traits can be dominant or recessive, and the recessive traits were obscured by the dominant ones in the F1.
e) the mechanism controlling the appearance of traits was different between the F1 and the F2 plants.

Answer 20

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

Question 21

Mendel’s observation of the segregation of alleles in gamete formation has its basis in which of the following phases of cell division?

a) anaphase II of meiosis
b) anaphase I of meiosis
c) prophase I of meiosis
d) metaphase I of meiosis
e) anaphase of mitosis

Answer 21

b) anaphase I of meiosis

Question 22

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) 1/4
b) 0
c) 1/2
d) 1
e) 1/6

Answer 22

b) 0

Question 23

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) 3/16
c) 9/16
d) 1/16
e) 1/2

Answer 23

e) 1/2

Question 24

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

Answer 24

e) 1/64

Question 25

Mendel’s second law of independent assortment has its basis in which of the following events of meiosis I?

a) separation of homologues at anaphase
b) alignment of tetrads at the equator
c) separation of cells at telophase
d) synapsis of homologous chromosomes
e) crossing over

Answer 25

b) alignment of tetrads at the equator

Question 26

Chromatids are separated from each other.

a) The statement is true for mitosis only.
b) The statement is true for meiosis I only.
c) The statement is true for meiosis II only.
d) The statement is true for mitosis and meiosis I.
e) The statement is true for mitosis and meiosis II.

Answer 26

e) The statement is true for mitosis and meiosis II.

Question 27

At which stage of mitosis are chromosomes usually photographed in the preparation of a karyotype?

a) anaphase
b) telophase
c) interphase
d) metaphase
e) prophase

Answer 27

d) metaphase

anaphase???

Question 28

A cell divides to produce two daughter cells that are genetically different.

a) The statement is true for mitosis only.
b) The statement is true for meiosis I only.
c) The statement is true for meiosis II only.
d) The statement is true for mitosis and meiosis I.
e) The statement is true for mitosis and meiosis II.

Answer 28

b) The statement is true for meiosis I only.

Question 29

If a horticulturist breeding gardenias succeeds in having a single plant with a particularly desirable set of traits, which of the following would be her most probable and efficient route to establishing a line of such plants?

a) Clone the plant asexually to produce an identical one.
b) Add nitrogen to the soil of the offspring of this plant so the desired traits continue.
c) Breed this plant with another plant with much weaker traits.
d) Force the plant to self-pollinate to obtain an identical one.

Answer 29

a) Clone the plant asexually to produce an identical one.

Question 30

Which of the following is a true statement about sexual vs. asexual reproduction?

a) In asexual reproduction, offspring are produced by fertilization without meiosis.
b) Sexual reproduction requires that parents be diploid.
c) Asexual reproduction produces only haploid offspring.
d) Asexual reproduction, but not sexual reproduction, is characteristic of plants and fungi.
e) In sexual reproduction, individuals transmit 50% of their genes to each of their offspring.

Answer 30

e) In sexual reproduction, individuals transmit 50% of their genes to each of their offspring.

Question 31

When homologous chromosomes cross over, what occurs?

a) Two chromatids get tangled, resulting in one re-sequencing its DNA.
b) Maternal alleles are “corrected” to be like paternal alleles and vice versa.
c) Two sister chromatids exchange identical pieces of DNA.
d) Each of the four DNA strands of a tetrad is broken and the pieces are mixed.
e) Specific proteins break the two strands and re-join them with their homologues.

Answer 31

e) Specific proteins break the two strands and re-join them with their homologues.

Question 32

A given organism has 46 chromosomes in its karyotype. We can therefore conclude which of the following?

a) It must be an animal.
b) It must be a primate.
c) It must be sexually reproducing.
d) It must be human.
e) Its gametes must have 23 chromosomes.

Answer 32

e) Its gametes must have 23 chromosomes.

Question 33

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) the tendency for dominant alleles to segregate together
d) different possible alignments of chromosomes
e) crossing over during prophase I

Answer 33

d) different possible alignments of chromosomes

Question 34

Why did the F1 offspring of Mendel’s classic pea cross always look like one of the two parental varieties?

a) The traits blended together during fertilization.
b) One phenotype was completely dominant over another.
c) Different genes interacted to produce the parental phenotype.
d) No genes interacted to produce the parental phenotype.
e) Each allele affected phenotypic expression.

Answer 34

b) One phenotype was completely dominant over another.

Question 35

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 characteristic.

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) purple and oval
b) red and long
c) purple and long
d) red and oval
e) white and long

Answer 35

c) purple and long

Question 36

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) The formation of gametes in plants occurs by mitosis only.
d) All of the genes controlling the traits were located on the same chromosome.
e) All of the genes controlling the traits behaved as if they were on different chromosomes.

Answer 36

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

Question 37

What was the most significant conclusion that Gregor Mendel drew from his experiments with pea plants?

a) Recessive genes occur more frequently in the F1 generation than do dominant ones.
b) An organism that is homozygous for many recessive traits is at a disadvantage.
c) There is considerable genetic variation in garden peas.
d) Genes are composed of DNA.
e) Traits are inherited in discrete units, and are not the results of “blending.”

Answer 37

e) Traits are inherited in discrete units, and are not the results of “blending.”

Question 38

When both traits are exhibited in the phenotype, it is said that the alleles display

a) gene silencing.
b) co-dominance.
c) incomplete dominance.
d) recessive traits.
e) complete dominance.

Answer 38

b) co-dominance.

Question 39

Which of the following occurs in meiosis but not in mitosis?

a) alignment of chromosomes at the equator
b) synapsis of chromosomes
c) production of daughter cells
d) condensation of chromatin
e) chromosome replication

Answer 39

b) synapsis of chromosomes

Question 40

Why did Mendel continue some of his experiments to the F2 or F3 generation?

a) to distinguish which alleles were segregating
b) to obtain a larger number of offspring on which to base statistics
c) to observe whether or not the dominant trait would reappear
d) to be able to describe the frequency of recombination
e) to observe whether or not a recessive trait would reappear

Answer 40

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

Question 41

Which of the following help(s) to hold the DNA strands apart while they are being replicated?

a) exonuclease
b) DNA polymerase
c) single-strand binding proteins
d) primase
e) ligase

Answer 41

c) single-strand binding proteins

Question 42

Cinnabar eyes is a sex-linked recessive characteristic in fruit flies. If a female having cinnabar eyes is crossed with a wild-type male, what percentage of the F1 males will have cinnabar eyes?

a) 0%
b) 25%
c) 50%
d) 75%
e) 100%

Answer 42

e) 100%

Question 43

In humans, male-pattern baldness is controlled by an autosomal gene that occurs in two allelic forms. Allele Hn determines nonbaldness, and allele Hb determines pattern baldness. In males, because of the presence of testosterone, allele Hb is dominant over Hn. If a man and woman both with genotype HnHb have a son, what is the chance that he will eventually be bald?

a) 0%
b) 25%
c) 33%
d) 50%
e) 75%

Answer 43

e) 75%

Question 44

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) HT
c) T
d) HhTt
e) Hh

Answer 44

b) HT

Question 45

In birds, sex is determined by a ZW chromosome scheme. Males are ZZ and females are ZW. A recessive lethal allele that causes death of the embryo is sometimes present on the Z chromosome in pigeons. What would be the sex ratio in the offspring of a cross between a male that is heterozygous for the lethal allele and a normal female?

a) 1:1 male to female
b) 2:1 male to female
c) 3:1 male to female
d) 4:3 male to female
e) 1:2 male to female

Answer 45

b) 2:1 male to female

Question 46

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) 25%
b) 0%
c) 75%
d) 100%
e) 50%

Answer 46

e) 50%

Question 47

When we see chiasmata under a microscope, that lets us know which of the following has occurred?

a) asexual reproduction
b) separation of homologues
c) anaphase II
d) prophase I
e) meiosis II

Answer 47

d) prophase I

Question 48

The following question refers to the essential steps in meiosis described below.

1. Formation of four new nuclei, each with half the chromosomes present in the parental nucleus
2. Alignment of tetrads at the metaphase plate
3. Separation of sister chromatids
4. Separation of the homologs; no uncoupling of the centromere
5. Synapsis; chromosomes moving to the middle of the cell in pairs

Which of the steps takes place in both mitosis and meiosis?

Answer 48

3

Question 49

How do cells at the completion of meiosis compare with cells that have replicated their DNA and are just about to begin meiosis?

a) They have the same number of chromosomes and half the amount of DNA.
b) They have half the number of chromosomes and half the amount of DNA.
c) They have half the amount of cytoplasm and twice the amount of DNA.
d) They have twice the amount of cytoplasm and half the amount of DNA.
e) They have half the number of chromosomes and one-fourth the amount of DNA.

Answer 49

e) They have half the number of chromosomes and one-fourth the amount of DNA.

Question 50

A certain gene found in a diploid species is known to have 18 alleles (variants). Any given organism of that species can/must have which of the following?

a) a haploid number of 9 chromosomes
b) up to 18 genes for that trait
c) up to, but not more than, 18 different traits
d) 2 alleles for that gene

Answer 50

d) 2 alleles for that gene

Question 51

Two plants are crossed, resulting in offspring with a 3:1 ratio for a particular trait. What does this suggest?

a) that the trait shows incomplete dominance
b) that the parents were true-breeding for contrasting traits
c) that each offspring has the same alleles for each of two traits
d) that the parents were both heterozygous for a single trait
e) that a blending of traits has occurred

Answer 51

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

Question 52

Which of the following differentiates between independent assortment and segregation?

a) The law of independent assortment is accounted for by observations of prophase I.
b) The law of segregation is accounted for by anaphase of mitosis.
c) The law of segregation requires describing two or more genes relative to one another.
d) The law of independent assortment requires describing two or more genes relative to one another.
e) The law of segregation requires having two or more generations to describe.

Answer 52

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

Question 53

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 colour and location assort independently.

If 1000 F2 offspring resulted from the cross, approximately how many of them would you expect to have red, terminal flowers?

a) 565
b) 190
c) 250
d) 65
e) 750

Answer 53

b) 190

Question 54

Tallness (T) in snapdragons is dominant to dwarfness (t), while red (R) flower colour is dominant to white (r). The heterozygous condition results in pink (Rr) flower colour.

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–tall and pink
c) ttrr–dwarf and white
d) TTRR–tall and red
e) TtRr–tall and red

Answer 54

b) TtRr–tall and pink

Question 55

A tetrad includes which of the following sets of DNA strands?

a) eight sets of sister chromatids
b) two sets of sister chromatids that have synapsed
c) four sets of sister chromatids
d) two single-stranded chromosomes that have synapsed
e) four sets of unique chromosomes

Answer 55

b) two sets of sister chromatids that have synapsed

Question 56

After telophase I of meiosis, the chromosomal makeup of each daughter cell is..?

a) haploid, and the chromosomes are each composed of two chromatids.
b) diploid, and the chromosomes are each composed of a single chromatid.
c) diploid, and the chromosomes are each composed of two chromatids.
d) tetraploid, and the chromosomes are each composed of two chromatids.
e) haploid, and the chromosomes are each composed of a single chromatid.

Answer 56

a) haploid, and the chromosomes are each composed of two chromatids.

Question 57

Eukaryotic sexual life cycles show tremendous variation. Which of the following characteristics do all sexual life cycles have in common?

I. Alternation of generations
II. Meiosis
III. Fertilization
IV. Gametes
V. Spores

Answer 57

II, III and IV

Question 58

Identify which stage the following occurs:

Homologous chromosomes are aligned at the equator of the spindle.

a) Prophase I
b) Metaphase I
c) Telophase I
d) Metaphase II

Answer 58

b) Metaphase I

Question 59

Identify which stage the following occurs:

Centromeres of sister chromatids disjoin and chromatids separate.

a) Anaphase I
b) Telophase I
c) Prophase II
d) Anaphase II

Answer 59

d) Anaphase II