Chapter 15—The Chromosomes of Organelles Outside the Nucleus Exhibit Non-Mendelian
Patterns of Inheritance
Fill in the Blank
1. When maternal and paternal gametes do not contribute equally to the inheritance of a
trait, we call this mode of inheritance ______________________________________.
Ans: non-mendelian
Difficulty: 1
2. In general, the genome of which organelles is larger — mammalian mitochondrion or
higher plant chloroplast? ______________________________________
Ans: chloroplast
Difficulty: 2
3. Because they do not carry all the genes they need to function and reproduce, and
because they need molecules encoded by nuclear genes, chloroplasts and mitochondria
are considered ________________________.
Ans: semiautonomous
Difficulty: 1
4. In the 1970s, Lynn Margulis and others proposed that today's chloroplasts and
mitochondria descended from prokaryotic ancestors in a theory called the
________________________________.
Ans: endosymbiont theory
Difficulty: 1
5. Allan Wilson and coworkers proposed all human mtDNA's today trace their ancestry to
a single mtDNA present in some distant ancestor. They call this human ancestor
________________________.
Ans: “mitochondrial Eve”
Difficulty: 1
6. If mtDNA sequences suggest a “mitochondrial Eve” because of strict maternal
inheritance, what type of human DNA sequences might show strict paternal inheritance
and point to “DNA Adam”? ______________________________________
Ans: Y-chromosome sequences
Difficulty: 3
7. In contrast with most nuclear DNA sequences, many mtDNA, cpDNA, and human Y
chromosomes all show what mode of transmission?
______________________________________
Ans: uniparental inheritance
Difficulty: 2
Page 281
8. Reciprocal crosses of green and variegated geraniums show what mode of transmission
of the organelles responsible for variegation?
______________________________________
Ans: biparental inheritance
Difficulty: 2
9. A device used to inject microscopic DNA-coated metal particles into cells is called a
______________________________________.
Ans: gene gun
Difficulty: 1
10. A burst of mitochondrial activity increases the temperature in the bloom of the
______________________________________.
Ans: voodoo lily
Difficulty: 1
11. The chlorophyll, the light-absorbing molecules, and the proteins of the photosynthetic
electron transport system are located in the
______________________________________.
Ans: thylakoid membranes
Difficulty: 1
12. Cells that carry a mixture of organelle genomes are referred to as
_______________________.
Ans: heteroplasmic
Difficulty: 1
13. The single mitochondrion of the protozoan Trypanosoma is known as a
____________________.
Ans: kinetoplast
Difficulty: 2
14. The process that converts pre-mRNAs to mature mRNAs is called
_______________________.
Ans: RNA editing
Difficulty: 1
15. In trypanosome mitochondria, the “workbench” where RNA editing takes places is
called a ______________________________________.
Ans: editosome
Difficulty: 2
Page 282
16. Evidence suggests that the women carrying the ancestral mtDNA for today's humans
lived in sub-Saharan Africa roughly how many years ago?
______________________________________
Ans: 200,000 years ago
Difficulty:
Multiple Choice
17.
A)
B)
C)
D)
Traits showing non-Mendelian extranuclear inheritance are inherited:
always from the mother.
always from the father.
always both parents.
depending on species, inheritance could be from mother, father, or both parents.
Ans: D
Difficulty: 2
18. With traits showing maternal inheritance, such as leaf variegation in four o'clocks,
reciprocal crosses usually:
A) yield the same results.
B) yield different results.
C) yield result which can seldom be predicted.
D) eliminate the need for sexual reproduction.
Ans: B
Difficulty: 1
19. When eukaryotic cells are stained with DNA-specific dyes and viewed under the light
microscope, DNA molecules are revealed:
A) in the nucleus.
B) in the matrix of the mitochondrion.
C) in the stroma of chloroplasts.
D) in all theses places: nucleus, mitochondrion, and chloroplast.
Ans: D
Difficulty: 1
20.
A)
B)
C)
D)
The molecules used in a chloroplast to carry out photosynthesis:
all are encoded by chloroplast DNA.
some are encoded by chloroplast DNA, other by nuclear DNA.
all are encoded by nuclear DNA.
some are encoded in nuclear DNA and some in mitochondrial DNA.
Ans: B
Difficulty: 2
Page 283
21.
A)
B)
C)
D)
E)
Which process(es) take place in the mitochondrion?
Krebs cycle
Calvin cycle
oxidative phosphorylation of ADP to ATP
both Krebs cycle and oxidative phosphorylation of ADP to ATP
both Calvin cycle and oxidative phosphorylation of ADP to ATP
Ans: D
Difficulty: 2
22.
A)
B)
C)
D)
A chloroplast URF is best described as:
a cpDNA coding sequence with product of unknown function.
a cpDNA intron, interrupting chloroplast coding sequences.
a chloroplast operon, including several structural genes.
an extraterrestrial sequence occurring as a symbiont.
Ans: A
Difficulty: 1
23. Based on rRNA coding sequences in mtDNA, cpDNA, and bacterial DNA, it has been
suggested that many mitochondrial genomes may be derived from a common ancestor
of:
A) chloroplasts.
B) cyanobacteria.
C) gram-negative non-sulfur purple bacteria.
D) prochlorophyte bacteria.
Ans: C
Difficulty: 2
24. Based on rRNA coding sequences in mtDNA, cpDNA, and bacterial DNA, it has been
suggested that modern chloroplast genomes may be derived from:
A) mitochondria.
B) cyanobacteria.
C) gram-negative non-sulfur purple bacteria.
D) chemautotrophic thermophilic bacteria.
Ans: B
Difficulty: 2
25. Which of the following is not accurate with regard to organelle genomes?
A) mtDNA and cpDNA are usually organized into nucleosomes by histones.
B) Mitochondrial translation is often inhibited by bacterial antibiotics (e.g.,
chloramphenicol).
C) Like bacteria, mitochondria use N-formyl methionine and tRNAfmet in translation.
D) All of the above are accurate.
Ans: A
Difficulty: 3
Page 284
26.
A)
B)
C)
D)
Molecular evidence suggests that DNA sequences may have been transferred between:
mtDNA and nuclear DNA.
cpDNA and mtDNA.
different cpDNA molecules.
evidence suggests all of the above have occurred.
Ans: D
Difficulty: 4
27. Which sequences would be most similar to the prevailing mtDNA sequences in today's
human populations?
A) mtDNA in “mitochondrial Eve”
B) Neanderthal mtDNA
C) mtDNA from a 4,000-year-old Egyptian mummy
D) Chimpanzee mtDNA
Ans: C
Difficulty: 3
28. Which type of DNA sequences might be studied to help reunite displaced children with
their families?
A) mtDNA sequences
B) cpDNA sequences
C) Y-chromosome sequences
D) highly conserved nuclear sequences
Ans: A
Difficulty: 2
29. Which type of DNA sequences might be studied to help determine the identity of a
particular variety of a cultivated crop?
A) mtDNA sequences
B) cpDNA sequences
C) Y-chromosome sequences
D) highly conserved nuclear sequences
Ans: B
Difficulty: 2
30.
A)
B)
C)
D)
Variegated four o'clock leaves have white patches among the green areas due to:
a mtDNA mutation which blocks electron transport.
a cpDNA mutation which incapacitates proteins essential for photosynthesis.
a nuclear DNA mutation, which leads to mosaicism.
both b and c
Ans: B
Difficulty: 1
Page 285
31. Xenopus borealis eggs are fertilized with sperm from a Xenopus laevis. In various tests,
the mtDNA of the F1 hybrids is probed with mtDNA from both parental species. Which
result is most likely?
A) Only probe from X. borealis hybridizes with the F1 DNA.
B) Only probe from X. laevis hybridizes with the F1 DNA.
C) Probes from both X. borealis and X. laevis hybridize with the F1 DNA, but X. borealis
probe hybridizes more efficiently.
D) Probes from both X. borealis and X. laevis hybridize with the F1 DNA, but X. laevis
probe hybridizes more efficiently.
Ans: C
Difficulty: 4
32. If the above study were repeated with Xenopus laevis eggs and Xenopus borealis sperm,
what result would be most likely?
A) Only probe from X. borealis hybridizes with the F1 DNA.
B) Only probe from X. laevis hybridizes with the F1 DNA.
C) Probes from both X. borealis and X. laevis hybridize with the F1 DNA, but X. borealis
probe hybridizes more efficiently.
D) Probes from both X. borealis and X. laevis hybridize with the F1 DNA, but X. laevis
probe hybridizes more efficiently.
Ans: D
Difficulty: 2
33.
A)
B)
C)
D)
Which of the genes is encoded by a chloroplast DNA sequence?
The yellow 1 mutant in Chlamydomonas.
Rubisco large subunit.
Mating type in Chlamydomonas.
The NADH dehydrogenase gene responsible for LHON.
Ans: B
Difficulty: 2
34. Consider the following “cross” between different Chlamydomonas mating types:
yellow-1+ / streptomycin-resistant  yellow-1- / streptomycin-sensitive
Which of the following ratios might be observed in the resulting haploid progeny?
A) (2) yellow-1+/streptomycin-resistant : (2) yellow-1–/streptomycin-resistant
B) (2) yellow-1+/streptomycin-resistant : (2) yellow-1–/streptomycin-sensitive
C) (4) yellow-1+/streptomycin-resistant : (0) yellow-1–/streptomycin-resistant
D) (1) yellow-1+ : (1) yellow-1– : (2) streptomycin-resistant : (0) / streptomycin-sensitive
Ans: A
Difficulty: 4
Page 286
35.
A)
B)
C)
D)
Which of the following statements is correct with respect to mitochondrial genes?
They are transmitted, largely intact, from parent to offspring.
Their inheritance shows Mendel's principle of segregation.
Their inheritance shows Mendel's principle of independent assortment.
All of the above
Ans: A
Difficulty: 3
36. After a cross between cells of two genetically different yeast strains, a number of
diploid cells are formed during a period of vegetative growth. Which of the following
is(are) correct regarding marker genes from the two parent strains, when observed in
cells shortly after hybridization?
A) Mitochondrial genetic markers from both parents are present.
B) Nuclear genetic markers from both parents are present.
C) Both mitochondrial and nuclear markers from both parents are present.
D) Mitochondrial and nuclear markers from only one parent are observed.
Ans: C
Difficulty: 3
37. In the same cross between yeast strains as above, which would be correct regarding
colonies from diploid cells after several generations of vegetative growth following
hybridization?
A) A colony shows mitochondrial genetic marker of one parental strain, but not both.
B) Nuclear genetic markers from both parents are present in all colonies.
C) Both mitochondrial and nuclear markers from only one parent are observed.
D) a and b
Ans: D
Difficulty: 3
38.
A)
B)
C)
D)
A researcher hopes that, after being shot with a gene gun, a plant cell will:
die.
incorporate foreign DNA into its nucleus.
mutate to a new genotype.
show uniparental inheritance.
Ans: B
Difficulty: 1
39.
A)
B)
C)
D)
A homoplasmic cell carries:
a mixture of organelle genomes.
only one type of organelle DNA.
only one mitochondrion.
two identical nuclei.
Ans: B
Difficulty: 1
Page 287
40.
A)
B)
C)
D)
A parasitic protozoan like Trypanosoma or Leishmania might have its mtDNA in:
many mitochondria.
a kinetoplast.
minicircles and maxicircles.
b and c
Ans: D
Difficulty: 3
41.
A)
B)
C)
D)
Inhibitors of bacterial translation, such as chloramphenicol and erythromycin, generally:
are inhibitors of eukaryotic cytoplasmic protein synthesis.
are inhibitors of mitochondrial protein synthesis.
have no effect on mitochondrial protein synthesis.
a and c
Ans: B
Difficulty: 3
42.
A)
B)
C)
D)
cpDNA-encoded proteins include:
RNA polymerase.
RNA polymerase and translation factors.
RNA polymerase. translation factors, and ribosomal proteins.
none of the above
Ans: C
Difficulty: 2
43.
A)
B)
C)
D)
The codon “UGA” specifies:
“stop” in the “universal” genetic code.
the amino acid tryptophan in human mtDNA.
formyl-methionine in mtDNA.
a and b
Ans: D
Difficulty: 3
44.
A)
B)
C)
D)
Which of the following has been associated with aging in humans?
Loss of mitochondria.
5kb and 7.4kb deletions in mtDNA of heart cells.
Loss of cytochrome oxidase c genes.
All of the above
Ans: B
Difficulty: 2
Page 288
45.
A)
B)
C)
D)
Which of the following has been associated with Alzheimer's Disease?
Loss of mitochondria.
5kb and 7.4kb deletions in mtDNA of heart cells.
Mutations in cytochrome oxidase c genes in brain cells.
All of the above
Ans: C
Difficulty: 2
46.
A)
B)
C)
D)
The genomes of organelles inherited in a biparental fashion show:
mitotic segregation.
meiotic segregation.
blending inheritance.
Mendelian inheritance.
Ans: A
Difficulty: 3
Matching
Match the item with the correct answer below
a. leaf variegation
b. petite colonies
c. NADP
d. NAD
e. Rubisco LSU
f. Rubisco SSU
47. encoded by nuclear gene
Ans: f
Difficulty: 2
48. chloroplast dinucleotide
Ans: c
Difficulty: 1
49. maternal-chloroplast inherited
Ans: a
Difficulty: 2
50. encoded by chloroplast gene
Ans: e
Difficulty: 2
51. mitochondrion dinucleotide
Ans: d
Difficulty: 1
Page 289
52. due to mitochondrial mutation
Ans: b
Difficulty: 2
Match the item with the correct answer below
a. resistant to chloramphenicol
b. petite mutant yeast cells
c. mutant mtDNA tRNALys
d. a mutant nuclear gene in Chlamydomonas
e. mutant mitochondrial electron transport enzyme
f. a mating type among haploid yeast cells
53. MERFF
Ans: c
Difficulty: 1
54. LHON
Ans: e
Difficulty: 1
55. Cr
Ans: a
Difficulty: 1
56. rho–
Ans: b
Difficulty: 1
57. MATa
Ans: f
Difficulty: 1
58. yellow 1–
Ans: d
Difficulty: 1
Match the item with the correct answer below
a. a unicellular alga
b. a frog
c. a liverwort
d. a parasitic protozoan
e. a variegated geranium
f. brewer's yeast
Page 290
59. Plasmodium falciparum
Ans: d
Difficulty: 1
60. Chlamydomonas reinhartii
Ans: a
Difficulty: 1
61. Pelargonium zonale
Ans: e
Difficulty: 1
62. Saccharomyces cerevisiae
Ans: f
Difficulty: 1
63. Marchantia polymorpha
Ans: c
Difficulty: 1
64. Xenopus laevis
Ans: b
Difficulty: 1
Match the item with the correct answer below
a. 0.5kb - 2.5kb
b. 16.5kb
c. 21kb - 31kb
d. 55kDa
e. 186kb
f. 120kb - 217 kb
65. human mitochondrial genome
Ans: b
Difficulty: 2
66. Marchantia mitochondrial genome
Ans: e
Difficulty: 2
67. Rubisco LSU size
Ans: d
Difficulty: 2
Page 291
68. chloroplast genomes
Ans: f
Difficulty: 2
69. kinetoplast minicircle
Ans: a
Difficulty: 2
70. kinetoplast maxicircle
Ans: c
Difficulty: 2
True or False
71. Genomes of organelles are inherited exactly as nuclear chromosomes.
Ans: False
Difficulty: 2
72. Most mitochondrial genomes are linear dsDNA molecules.
Ans: False
Difficulty: 2
73. Human mitochondrial DNA contains tightly packed genes without introns.
Ans: True
Difficulty: 1
74. Yeast have a larger mitochondrial genome and unlike human mtDNA genes, yeast
mtDNA code for genes with introns.
Ans: True
Difficulty: 1
75. Plant mitochondrial genomes are smaller than animal mitochondrial genomes.
Ans: False
Difficulty: 2
76. The universal code of DNA also applies to mtDNA.
Ans: False
Difficulty: 2
77. RNA editing can occur in mitochondrial transcripts and is the addition and/or deletion
of uracils and/or cytosines, which results in codon changes from the original DNA.
Ans: True
Difficulty: 1
Page 292
78. Mitochondrial DNA has an approximately 10-fold higher rate of mutation compared to
nuclear DNA.
Ans: True
Difficulty: 1
79. In uniparental inheritance, transmission is usually maternal.
Ans: True
Difficulty: 1
80. Heteroplasmic cells lead to earlier appearance of mitochondrial-inherited disease
compared to homoplasmic cells.
Ans: False
Difficulty: 2
81. The proportion of mutant mtDNAs and the tissue in which they reside influence
phenotype.
Ans: True
Difficulty: 1
82. Mutations in mtDNA are often caused by free-radical damage, which results from
oxidative phosphorylation.
Ans: True
Difficulty: 1
83. Oxidative phosphorylation decreases with age.
Ans: True
Difficulty: 1
84. Mitochondria in brain cells of patients with symptoms of Alzheimer's disease have
unusually high energy metabolism.
Ans: False
Difficulty: 2
85. Mitochondria and chloroplasts are considered to be semiautonomous.
Ans: True
Difficulty: 1
Short Answer
86. Why does organelle DNA often have a buoyant density different from the cell's nuclear
DNA?
Ans: Different base composition; different AT:GC ratio.
Difficulty: 3
Page 293
87. What is an explanation of the observation that mtDNA evolves almost ten times more
rapidly than nuclear DNA in the same species?
Ans: More errors in replication and less efficient repair mechanism.
Difficulty: 3
88. Why is the mode of transmission of streptomycin resistance in Chlamydomonas said to
be “uniparental inheritance” rather than “maternal inheritance”?
Ans: Chlamydomonas is isogamous, gametes are neither “egg” nor “sperm.”
Difficulty: 2
89. Is the so-called “universal” genetic code truly universal? Why or why not?
Ans: No. There are several different codon assignments in mitochondria, for example.
Difficulty: 3
90. Why do scientists believe the COXII gene transferred from the mtDNA to the nuclear
genome, via an RNA intermediate, in some plants?
Ans: The mtDNA COXII pseudogene has an intron, which the nuclear sequence lacks.
Difficulty: 4
91. Why might the brain cells show abnormally low energy metabolism in individuals with
Alzheimer's Disease?
Ans: Defective mitochondrial cytochrome oxidase genes may reduce energy
metabolism.
Difficulty: 2
92. How does mtDNA variation provide evidence that modern humans emerged in Africa?
Ans: More sequence differences among Africans, due to longer time to accumulate
mutations.
Difficulty: 4
93. The “Endosymbiont” hypothesis posited by Lynn Margulis in the 1970's is now
considered a “theory.” What molecular evidence strongly supports the hypothesis to the
point where it is now accepted as a theory?
Ans: 1. both mitochondria and chloroplasts have their own DNA, which replicates
independently of the nuclear genome. 2. like the DNA of bacteria, mtDNA and
cpDNA are not organized into nucleosomes by histones. 3. mitochondrial
genomes use N-formyl methionine as the “start” amino acid. 4. inhibitors of
bacterial translation also inhibit mitochondrial translation.
Difficulty: 3
Page 294
94. Explain how mitochondrial traits are inherited.
Ans: Mitochondrial traits are inherited in a non-Mendelian fashion. Because
mitochodria are not separated like chromosomes in cell division, equal
segregation is not seen. Also mitochondria are usually maternally inherited in
diploids, but can be paternal or biparentially inherited in some cases.
Difficulty: 2
95. What is RNA editing?
Ans: RNA editing is a molecular mechanism by which pre-mRNA is converted to
mature mRNA through the unusual insertion and/or deletion of either uracils or
cytosines. Without the editing the message does not correctly code for the protein
produced. In other words, the DNA contains only bits and pieces of the actual
gene which is added to or clipped prior to translation.
Difficulty: 3
Experimental Design and Interpretation of Data
96. A scientist studies matings between yeast cells of the grande and petite forms; after
sporulation, what types of yeast colonies will result from the spores produced, and in
what proportions?
Ans: 4 grande: 0 petite.
Difficulty: 2
97. Why might a researcher attach a gene encoding a green fluorescent protein to a DNA
sequence before transforming a cell's mtDNA?
Ans: To confirm successful transformation by detecting fluorescence in the target.
Difficulty: 2
98. Identical twins arise from a single zygote. One twin has symptoms of MERFF but the
other twin does not show the disorder. Explain how this might happen.
Ans: Unequal distribution of mitochondria during initial cell division and development.
Difficulty: 3
99. Mom 1 and Mom 2 both show a hypothetical mitochondrial-related phenotype and
neither Father is effected. Both families have four kids. The kids of family 1 are all
affected but only half of the kids of family 2 show the phenotype. Interpret this result
with respect to the genotype of Moms 1 and 2.
Ans: Mom 1 is homoplasmic and Mom 2 is heteroplasmic for the hypothetical
phenotype.
Difficulty: 2
Page 295
100. Statistical calculations and assumptions regarding mutation rates are utilized in
evolutionary biology. Two hypotheses exist regarding the evolution of humans. One,
called the replacement theory, hypothesizes that man existed in parallel to other hominid
species and simply out-competed them to exist today. The second hypothesis is that
modern man is a direct descendent of Neanderthal man but that by random genetic loss
or negative selection large sequence discrepancies exist between the species. What
discovery and experiment is needed to test these two mutually exclusive hypotheses?
Ans: The discovery and testing of a North African Neanderthal mtDNA. Analysis of
Cro-Magnon mitochondrial DNA could also be supportive of one or the other
hypothesis.
Difficulty: 3
Page 296