Exam 1
BIOL 221
1. 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
B) true-breeding
C) incomplete dominance
D) adihybrid cross
2. Which of the following is true of a species that has a chromosome number of 2n = 16?
A) The species is diploid with 32 chromosomes per cell.
B) The species has 16 sets of chromosomes per cell.
C) Each cell has 8 homologous pairs.
D) During the S phase of the cell cycle there will be 32 separate chromosomes.
E) A gamete from this species has 4 chromosomes
3. What is a sister chromatid?
A) a chromosome in G1 of the cell cycle
B) a replicate of a chromosome
C) a chromosome found outside the nucleus
D) a special region that holds two centromeres together
4. When Thomas Hunt Morgan crossed his red-eyed F1 generation flies to each other, the F2 generation included both red- and white-eyed flies. Remarkably, all the white- eyed flies were male. What was the explanation for this result?
A) The gene involved is on the X chromosome.
B) The gene involved is on the Y chromosome.
C) The gene involved is on an autosome.
D) Other male-specific factors influence eye color in flies.
E) Other female-specific factors influence eye color in flies
5. Males are more often affected by sex-linked traits than females because
A) X chromosomes in males generally have more mutations than X chromosomes in females
B) male hormones such as testosterone often alter the effects of mutations on the X chromosome
C) female hormones such as estrogen often compensate for the effects of mutations on the X
D) males are hemizygous for the X chromosome
E) mutations on the Y chromosome often worsen the effects of X-linked mutations
6. 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 "blending"
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
7. How do the daughter cells at the end of mitosis and cytokinesis compare with their parent cell when it was in G1 of the cell cycle?
A) The daughter cells have half the amount of cytoplasm and half the amount of DNA.
B) The daughter cells have half the number of chromosomes and half the amount of DNA.
C) The daughter cells have the same number of chromosomes and half the amount of DNA.
D) The daughter cells have the same number of chromosomes and the same amount of DNA.
E) The daughter cells have the same number of chromosomes and twice the amount of DNA.
8. After telophase I of meiosis, the chromosomal makeup of each daughter cell is
A) diploid, and the chromosomes are each composed of a single chromatid
B) diploid, and the chromosomes are each composed of two sister chromatids
C) haploid, and the chromosomes are each composed of a single chromatid
D) haploid, and the chromosomes are each composed of two sister chromatids
E) tetraploid, and the chromosomes are each composed of two sister chromatids
9. 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
For the following questions, match the key event of meiosis with the stages listed below.
I.Prophase IV.Prophase II
II.Metaphase IVI.Metaphase II
III.Anaphase IVII.Anaphase II
IV.Telophase IVIII.Telophase II
10. Tetrads of chromosomes are aligned at the equator of the spindle; alignment determines independent assortment.
A) I
B) II
C) IV
D) VII
E) VIII
11. Synapsis of homologous pairs occurs; crossing over may occur.
A) I
B) II
C) IV
D) VI
E) VII
12. Centromeres of sister chromatids disjoin and chromatids separate.
A) II
B) III
C) IV
D) V
E) VII
13. A localized group of organisms that belong to the same species and are actively interbreeding is called a
A) biosystem.
B) community.
C) population.
D) ecosystem.
E) family.
14. Which phase includes centromeres uncoupling, sister chromatids separating, and the two new chromosomes moving to opposite poles of the cell?
A) telophase
B) anaphase
C) prometaphase
D) metaphase
E) prophase
15. SRY is best described in which of the following ways?
A) A gene region present on the Y chromosome that triggers male development
B) A gene present on the X chromosome that triggers female development
C) An autosomal gene that is required for the expression of genes on the Y chromosome
D) An autosomal gene that is required for the expression of genes on the X chromosome
E) Required for development, and males or females lacking the gene do not survive past early childhood
16. 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%
17. If cells in the process of dividing are subjected to colchicine, a drug that interferes with the functioning of the spindle apparatus and causes a failure at the M check- point, at which stage will mitosis be arrested?
A) anaphase
B) prophase
C) telophase
D) metaphase
E) interphase
18. In cats, black (recessive) fur color is caused by an X-linked allele; the other allele at this locus causes orange color (recessive). The heterozygote is calico (tortoiseshell). What kinds of offspring would you expect from the cross of a black female and an orange male?
A) Calico females; calico males
B) Black females; orange males
C) Orange females; orange males
D) Calico females; black males
E) Orange females; black males
19. If there are 20 chromatids in a cell at metaphase of mitosis, how many chromosomes are there in each daughter cell following cytokinesis?
A) 10
B) 20
C) 30
D) 40
E) 80
20. Red-green color blindness is a sex-linked recessive trait in humans. Two people with normal color vision have a color-blind son. What are the genotypes of the parents?
A) XcXc and XCY
B) XcXc and XCY
C) XCXC and XcY
D) XCXC and XCY
E) XCXc and XCY
21. 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
22. Mendel's 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
23. 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) 2:1 male to female
B) 1:2 male to female
C) 1:1 male to female
D) 4:3 male to female
E) 3:1 male to female
24. Which of the following occurs in meiosis but not in mitosis?
A) Chromosome replication
B) Synapsis of chromosomes
C) Production of daughter cells
D) Alignment of chromosomes at the equator
E) Condensation of chromatin
25. Where do the microtubules of the spindle originate during mitosis in animal cells?
A) centromere
B) centrosome
C) centriole
D) chromatid
E) kinetochore
26. Regarding mitosis and cytokinesis, one difference between higher plants and animals is that in plants
A) the spindles contain microfibrils in addition to microtubules, whereas animal spindles do not contain microfibrils.
B) sister chromatids are identical, but they differ from one another in animals.
C) a cell plate begins to form at telophase, whereas in animals a cleavage furrow is initiated at that stage.
D) chromosomes become attached to the spindle at prophase, whereas in animals chromosomes do not become attached until anaphase.
E) spindle poles contain centrioles, whereas spindle poles in animals do not.
27. Chiasmata (more than one chiasma) are what we see under a microscope that let us know which of the following is occurring?
A) Asexual reproduction
B) Meiosis II
C) Anaphase II
D) Crossing over
E) Separation of homologs
28. 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%
29. 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?
A) 1/16
B) 3/16
C) 3/8
D) 1/2
E) 9/16
30. Chromosomes first become visible during which phase of mitosis?
A) prometaphase
B) telophase
C) prophase
D) metaphase
E) anaphase
Refer to the following information to answer the questions below.
A man who is an achondroplastic dwarf with normal vision marries a color-blind woman of normal height. The man's father was six feet tall, and both the woman's parents were of average height. Achondroplastic dwarfism is autosomal dominant, and red-green color blindness is X-linked recessive.
31. How many of their daughters might be expected to be color-blind dwarfs (but not dwarves!)?
A) All
B) None
C) Half
D) One out of four
E) Three out of four
32. What proportion of their sons would be color-blind and of normal height?
A) All
B) None
C) Half
D) One out of four
E) Three out of four
33. How does sexual reproduction increase the genetic variation in a species?
A) By allowing independent assortment of chromosomes
B) By allowing fertilization
C) By increasing gene stability
D) By conserving chromosomal gene order
E) By decreasing mutation frequency
34. 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?
A) 0%
B) 25%
C) 50%
D) 75%
E) 100%
35. What type of inheritance is seen in #34 above?
A) Standard dominant/recessive
B) Codominance
C) Incomplete dominance
D) X-linked inheritance
36. When pairs of homologous chromosomes separate during anaphase I,
A) the maternal chromosomes all move to the same daughter cell.
B) the sister chromatids remain attached to one another.
C) recombination is not yet complete.
D) thesynaptonemal complex is visible under the light microscope
Refer to the following to answer the questions below.
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 cactuses have spines. Homozygous recessive nn cactuses have no spines at all.
37. The relationship between genes S and N is an example of
A) incomplete dominance
B) epistasis
C) complete dominance
D) pleiotropy
E) codominance
38. 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
The following is a map of four genes on a chromosome:
39. Between which two genes would you expect the highest frequency of recombination?
A) A and W
B) W and E
C) E and G
D) A and E
E) A and G
40. What is the reason that linked genes are inherited together?
A) They are located close together on the same chromosome.
B) The number of genes in a cell is greater than the number of chromosomes.
C) Chromosomes are unbreakable.
D) Alleles are paired together during meiosis.
E) Genes align that way during metaphase I of meiosis
41. Cells that are in a permanent non-dividing state are in which phase?
A) G0
B) G2
C) G1
D) S
E) M
42. Meiosis II is similar to mitosis in that
A)the daughter cells are diploid
B) DNA replicates before the division
C) sister chromatids separate during anaphase
D)homologous chromosomes synapse
E) the chromosome number is reduced
43. If nondisjunction occurs in meiosis II during gametogenesis, what will be the result at the completion of meiosis?
A) All the gametes will be diploid
B) Half of the gametes will be n + 1, and half will be n - 1
C) 1/4 of the gametes will be n + 1, one will be n - 1, and two will be n
D) There will be three extra gametes
E) Two of the four gametes will be haploid, and two will be diploid
44. If a cell becomes cancerous, develops a tumor, and becomes metastatic it is typically due to thefailure of cell cycle control mechanisms. Which of the following is a type of cell cycle control that would have to fail for this to occur.
A)Anchorage dependence
B)Density dependence
C)Chemical dependence
D)A and B
E)None of the above
45. What is aneuploidy?
A)More than one copy of all chromosomes in the genome
B)More than three copies of all chromosomes in the genome
C)More or fewer copies of a single chromosome than is normal for the study organism
D)The complete loss of all copies of a single chromosome
E)The loss or addition of a single chromatid arm
46. What is the cellular process that leads to some cats being calico?
A)Gene silencing
B)Epigenetics
C)X inactivation
D)Pleiotropy
E)Hybridization
47. What process may separate linked genes in gamete formation?
A)Independent assortment
B)X inactivation
C)Cytokinesis
D)Synapse formation
E)Crossing-over
48. The locus for gene B is 8.9 centiMorgans from the locus for gene A. The locus for gene D is 12.7 centiMorgans from gene C. Which two linked genes are most likely to NOT be inherited together?
A)A and B
B)C and D
C)Cannot tell from the data provided
D)None of the above
49. Sometimes in Meiosis I, Anaphase I, two homologous chromosomes fail to separate. This event is called…
A)Chromosomal conjoinment
B)Non-disjunction
C)Aneuploidy
D)Chromosomal synapse
E)This never occurs
50. The human ABO blood-groups show what two types of complex inheritance?
A)Co-dominance and polygenics
B)Pleiotropy and incomplete dominance
C)Epistasis and multiple alleles
D)Multiple alleles and co-dominance
E)Incomplete dominance and epistasis
Bonus
(4pts)
Using a Punnett square, complete the following tri-hybrid cross. Provide the outcome of phenotypic ratios.
A = amiable, a = meanB = big, b = littleC = cooperative, c = uncooperative
AaBbCc x AaBbCc