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Nuclear States Questions

Question 1

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Answer 1

In reference to the nuclei in a compartment, a diploid nucleus contains two sets of chromosomes in one nucleus. The dikaryotic compartment contains two genetically different sets of haploid nuclei, each with one set of chromosomes.

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Question 2

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Answer 2

Following contact between two compatible hyphae, the walls at the junction dissolve. The haploid nucleus from one mycelium passes into the compartment of the compatible fungus, divides mitotically, spreads through the mycelium, where two genetically different haploid nuclei subsequently coexist in each compartment.

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Question 3

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Answer 3

The most significant advantage is that selection takes place on the entire functional genome. Any disadvantageous traits are expressed and the individual removed. Dominance can only be expressed in the diploid individual, and by the time a diploid is formed, disadvantageous recessive alleles have been removed from the population. Surviving individuals will be well adapted to that environment.

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Question 4

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Answer 4

Its very hard to see how a fungus is advantaged by a multinuclear state unless it is through identical alleles in each nucleus producing particular enzymes in the compartment. The fungus would be able to control production of important enzymes by managing nuclei separately. Further, mutations in one nucleus might be masked, enabling the fungus to function normally. In the case of Rhizoctonia solani, the species has formed a diversity of biotypes, some of which are pathogens, others are saprotrophs, and yet others mycorrhizal fungi. As far as we can tell, the sexual state is rare outside the laboratory. Thus variation may become fixed in the populations following mutations in different nuclei.

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Question 5

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Question 6

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Question 7

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