Deck 24: DNA: The Genetic Material

Question 1

Mitochondria from which of the following model organisms utilize the universal genetic code in protein synthesis?

A) Arabidopsis thaliana, a mustard plant
B) Escherichia coli bacteria
C) Drosophila melanogaster, a fruit fly
D) Caenorhabditis elegans, a roundworm
E) Mus musculus, the house mouse

Answer 1

A

Question 2

Some parasitic or symbiotic organisms are passed from parent to offspring transovarially-through the egg-by invading the egg cytoplasm. A general term for this phenomenon is

A) infectious heredity.
B) extrachromosomal inheritance.
C) Lamarckian heredity.
D) parasitic inheritance.
E) extranuclear inheritance.

Answer 2

A

Question 3

Which of the following is lacking from animal mtDNA?

A) Complete stop codons
B) Histone proteins
C) Introns
D) Ribosomal protein genes
E) All of the above

Answer 3

E

Question 4

Which of the following is not a characteristic of non-Mendelian inheritance?

A) The results of reciprocal crosses involving extranuclear genes are not the same as reciprocal crosses involving nuclear genes.
B) Non-Mendelian inheritance is unaffected by substituting a nucleus with a different genotype.
C) Extranuclear genes cannot be mapped to the chromosomes in the nucleus.
D) Extranuclear inheritance is always maternal.
E) Ratios typical of Mendelian segregation are not found.

Question 5

Organellar DNA is typically

A) single stranded and linear.
B) single stranded and circular.
C) double stranded and circular.
D) double stranded and linear.
E) None of the above

Question 6

The phenomenon where the expression of certain genes is determined by whether they are inherited from the maternal parent or paternal parent is called

A) maternal inheritance.
B) maternal effect.
C) extranuclear inheritance.
D) genetic imprinting.
E) uniparental inheritance.

Question 7

Male sterility stemming from mtDNA mutation is termed

A) mitochondrial male sterility, or MMS.
B) extranuclear male sterility, or EMS.
C) mitochondrial emasculation, or ME.
D) cytoplasmic male sterility, or CMS.
E) mutational male sterility, or MMS.

Question 8

mRNAs transcribed in the mitochondria are translated in the

A) mitochondria.
B) cytoplasm.
C) nucleus.
D) All of the above
E) None of the above

Question 9

The neutral petites genotype of Saccaromyces would be lethal were it not for

A) nuclear-encoded and cytoplasmically localized fermentation.
B) mitochondrion-independence in yeast.
C) the genes of the chloroplast genome.
D) compensating mutations elsewhere in the genome.
E) all of the above.

Question 10

From the Chlamydomonas cross mt+ [eryr] × mt- [erys], most of the offspring

A) are erythromycin resistant.
B) whichever phenotype is shown by the female parent.
C) are mating type mt+.
D) are erythromycin sensitive.
E) whichever phenotype is shown by the male parent.

Question 11

Which of the following statements is true?

A) Mitochondrial genomes of different organisms are about the same size.
B) Mitochondrial DNA is typically biparentally inherited.
C) Mitochondrial genomes are almost identical to chloroplast genomes.
D) Mitochondrial genes are similar to bacterial genes in structure.
E) Mitochondrial DNA is rarely supercoiled.

Question 12

The endosymbiont theory posits that

A) chloroplasts are descended from photosynthetic bacteria.
B) Eukaryotic cells originally lacked mitochondria and chloroplasts.
C) mitochondria originated by free-living bacteria.
D) All of the above
E) None of the above

Question 13

Which of the following enzymes are required for mitochondrial function?

A) DNA polymerase
B) Aminoacyl synthetase
C) RNA polymerase
D) Cyclohexamide
E) Cytochrome oxidase

Question 14

In all plants, as in animals, extranuclear DNA is maternally inherited.

Question 15

Extranuclear inheritance refers to genes located in

A) the nucleus.
B) the chloroplasts.
C) the mitochondria.
D) A, B, and C
E) B and C only

Question 16

Cells with more than one mitochondrial genotype are

A) heteroplasmic.
B) polymorphic.
C) heterozygous.
D) homoplasmic.
E) homozygous.

Question 17

Chloroplasts are found in plant and some protist cells, while mitochondria are found in

A) animal cells.
B) plant and fungal cells.
C) animal, plant, protist, and fungal cells.
D) animal and plant cells.
E) animal and bacterial cells.

Question 18

In the maternal effect case of shell coiling in Limnaea snails, a Mendelian cross starting with a dextral (D/D) female and a sinistral (d/d) male yields ________ F2s.

A) all dextral
B) a 3:1 dextral:sinistral ratio
C) all sinistral
D) half dextral and half sinistral
E) None of the above

Question 19

A patrilineal analog of mitochondrial inheritance is

A) X-linked genes.
B) chloroplasts.
C) the Y chromosome.
D) A, B, and C
E) B and C only

Question 20

Which yeast mutant overcomes the wild-type mitochondria so that a respiratory-deficient phenotype results?

A) Suppressive grandes
B) Segregational petite
C) Suppressive petite
D) Neutral grandes
E) None of the above

Question 21

Human mtDNA is about 16,000 bp in size.

Question 22

In reciprocal crosses of animals, extranuclear inheritance typically results in the exclusive expression of the maternal phenotype.

Question 23

Purple nonsulfur photosynthetic bacteria are the group of bacteria most closely related to modern mitochondria. Does this mean that mitochondria evolved from these bacteria?

Question 24

Unlike nuclear DNA, replication of mitochondrial DNA is conservative.

Question 25

The endosymbiosis theory was proposed by Lynn Margulis in the 1980s. Her ideas met with much criticism early on, but ultimately prevailed. Margulis' arguments are a good example of using strong inference, making sense of multiple independent observations with a single explanatory hypothesis. In other words, in this way of investigating nature, seemingly independent observations present a pattern that can be used to deduce process. What are the seemingly independent observations of organellar DNA that make sense in light of the endosymbiosis explanation?

Question 26

The Malagasy people, who are native to the island of Madagascar off the African coast, are linguistically and phenotypically more similar to Indonesians than they are to mainland Africans. Outline a test of relationship using mitochondrial DNA.

Question 27

Certain sea turtles that feed along the coast of South America migrate hundreds of miles in open ocean back to their natal south Atlantic island beaches in order to breed. An intriguing hypothesis proposed by marine biologist Archie Carr in the 1980s suggested that turtles in these populations began this migration pattern millions of years ago when the continental coast was much closer to the islands. As the continents drifted, the turtles were forced to migrate farther and farther out to sea. Can you think of a way to use mtDNA to test this hypothesis?

Question 28

Mitochondrial and nuclear DNA differ in density, permitting separation with density gradient centrifugation. What is the source of this density difference?

Question 29

Some proteins consist of a combination of mitochondrial-encoded and nuclear-encoded subunits.

Question 30

The genetic code is universal, including organisms of all kingdoms and organellar DNA.

Question 31

The endosymbiotic hypothesis of mitochondrial origins suggests that modern-day mitochondria are descended from symbiotic bacteria, in particular an ancestral member of the purple nonsulfur photosynthetic bacterial group. How can evolutionary biologists be so specific as to group of origin? What kinds of analyses would help narrow down the possibilities, leading biologists to this group?

Question 32

A horticulturist who has not taken genetics is collecting seeds from flowers produced on different branches of a variegated plant. He separates and packages the seeds produced from normal green portions of the plant, from variegated branches, and from pure white portions, and markets them as normal, variegated, and albino varieties, respectively. Which patrons are likely to be unhappy with their purchase?

Question 33

The malarial protist Plasmodium, which is an obligate internal parasite of the blood of vertebrates, possesses a dysfunctional plastid. Formulate a hypothesis as to how this organism, which is never exposed to light, may have acquired its plastid. How could you test this hypothesis?

Question 34

Pigmentless chloroplasts are called albinoplasts.

Question 35

Maternal inheritance is also referred to as maternal effect.

Question 36

List some features of mitochondrial DNA that make these molecules so useful for population studies.

Question 37

Mitochondrial DNA is maternally inherited, so shouldn't patterns of mitochondrial inheritance and expression parallel that of X-linked genes? Why or why not?

Question 38

As a conservation geneticist, you are interested in saving the genetic heritage of an endangered bird species that has dwindled in population size to just a few individuals. You decide the best course of action is to attempt to hybridize these individuals with a related species. There are several species that look similar to the endangered bird species, but some are likely to be more closely related to it than others. How might you use mtDNA to help select the hybrid partner for your captive breeding program, and why might it be important to select the closest relative?

Question 39

Briefly explain how selective antibiotics can be used to investigate cytoplasmic vs. mitochondrial protein synthesis.

Question 40

In mitochondria, the initiator codon specifies F-met tRNA, as with nuclear genes.

Question 41

Lateral gene transfers between organellar and nuclear genomes appear to be very common. For example, an approximately 270-kb segment of Arabidopsis mitochondrial DNA is found in the nuclear genome of the plant (Lin et al. 1999. Nature 402: 761-768), and a 33-kb piece of chloroplast DNA is found on chromosome 10 in rice plants (Yuan et al. 2002. Mol. Genet. Genomics 267: 713-720). How do you suppose that DNA sequestered in organelles can be transferred to and integrated with nuclear DNA?

Question 42

Explain how the inheritance of dextral vs. sinistral coiling in Limnaea snails is an example of maternal effect but not maternal inheritance.

Question 43

Describe the pattern of inheritance you would expect if you crossed petite yeast mutants with wild-type (grande) individuals, if (a) the petite mutant is mitochondrial, or (b) the petite mutant is nuclear.