Heterokaryosis and Parasexuality
Heterokaryosis
Botrytis cinereus experiment (multinucleate spore0
How formed:
Germination of heterokaryotic spore
Mutation
Fusion of haploid nuclei
Hyphal fusion
Parasexuality (read pages 252-255 in the handout)
Aspergillus nidulans: conidia uninucleate; strains have yellow and green conidia and can synthesis biotin or thiamine
Experiment: strains (green, biotin+, thiamine-) and (yellow, biotin-, and thiamine +).
Mixed the two strains, eventually obtained
Green conidia and yellow conidia on the same head; could grow on minimal media and thus could synthesize biotin and thiamine.
Yellowish-green conidia that when plated out could grow on minimal media (i. e. media lacking in thiamine and biotin)
Continued to grow yellowish-green generations eventually obtained the following combinations
Yellow, biotin-, thiamine +
Green, biotin+, thiamine -
Yellow, biotin+, thiamine-
Green, biotin-, thiamine +
Means got recombination
Example of parasexual cycle: heterokaryosis to diploidization to haploidization
Explanation (see handout):
Mitotic crossing-over
Adaptability and Pleomorphism