Recent genetic studies of the structure of microsporidian genomes, as well as the sequences of their tubulin genes and the gene for RNA polymerase II, indicate that microsporidians are closely related to the fungi. Microsporidians lack flagella, centrioles, peroxisomes, and mitochondria (although they do have degenerate mitochondria, called mitosomes). They have the smallest genome of any eukaryote, and it is a genome that changes quickly. The genome is contained within two haploid nuclei. All microsporidians are obligate intracellular parasites. They use a unique organelle called a polar filament to gain access to the cells of their hosts. One species causes chronic diarrhea in AIDS patients. Another parasitizes Anopheles gambiae, the mosquito that transmits a fatal form of malaria to humans.
Given the eukaryotic structures they lack, it should be expected that microsporidians also lack
A) the "9 + 2 pattern" of microtubules.B) chitin.
C) lysosomes.
D) nuclei.
E) centrosomes.
Answer: A
The lifestyle of microsporidians is most similar to that of
A) scavengers.B) viruses.
C) free-living yeasts.
D) ectoparasites.
Answer: B
Which of the following microsporidian features are shared with many other fungi?
1. chitinous cell wall2. two haploid nuclei per cell
3. polar filament
4. chemoheterotrophy
A) 1 and 2
B) 1 and 3
C) 1 and 4
D) 1, 2, and 4
E) 2, 3, and 4
Answer: D
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