In this article we will discuss about: 1. Heterothallism in Fungi 2. Heterokaryosis in Fungi 3. Parasexuality. Heterothallism in Fungi: A. F. Blakeslee, an American. heterokaryosis The presence in the same cell of two or more genetically different nuclei. Heterokaryosis occurs naturally in certain fungi, in which it results from. Heterokaryosis, the association of genetically diverse nuclei in a system capable of propagation, is a phenomenon peculiar to, but common in, the fungi. During.

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Blakeslee coined the terms homothallism and heterothallism to explain this phenomenon. The term Heterokaryosis was proposed by Hansen and Smith hetrrokaryosiswho reported it for the first time in Botrytis cinerea. Every step differs drastically. A heterothallic species may not be of only two mating types. The segregation of the diploid strains occurs when uninucleate diploid conidia are formed. The requirement for the other thallus does not lie in morphologically distinct sex organs, but in genetically-different nuclei which are not available in the same mycelium.

Both the daughter nuclei are called aneuploidy. Heterokarylsis of these diseases result in problems in mucopolysaccharide metabolism. Because each style has its own formatting nuances that evolve over time fungo not all information is available for every reference entry or article, Encyclopedia. Blakeslee observed, that while some isolates of Mucor formed sporangia as well as zygospores e.


Sexually undifferentiated- The male and female sex organs are morphologically similar and, therefore, indistinguishable. Cite this article Pick a style below, inn copy the text for your bibliography. Majority 63 per cent of the heterothallic Basidiomycota are tetrapolar, forming four types of basidiospores. Home Science Dictionaries thesauruses pictures and press releases heterokaryosis.

The homothallic species were those that produced zygospores independently, while heterothallic species required the presence of the opposite mating type.


The spores give rise to two types of thalli, which must come together to bring together the two nuclei carrying the compatibility factors A and a. This situation is termed secondary homothallism.

When genetically divergent nuclei come together in the plasmodium form, cheaters have been shown to emerge. Thus, the hyphae produced behave as homothallic, though it involves genetically-different nuclei. However, if crossing over does not take place, heterokaryosiz two types of spores AB and ab or Ab and aB are formed and only two types of thalli are produced.

Such fungi need genetically-different nuclei, which does not occur when the same thallus forms both the sex organs.

heterokaryosis |

The heterothallic forms provide another example of physiological heterothallism. Heterokaryosis is often accompanied by parasexual cycle. Heterokaryosis can also be induced in vitroto study the interaction between the cellular components from different species see cell fusion.

Dioecious sexually dimorphic – The two sex organs are present on different thalli. The cell, and the hypha or mycelium containing hetedokaryosis, is known as a heterokaryon ; the most common type of heterokaryon is a dikaryon.


This is called morphological heterothallism. The Unit of Life for Class 11 Biology. Whatever be the reason for heterothallism, the fact remains that different thalli are needed for sexual reproduction. It is to the credit of microbial geneticists that a series of novel methods of genetic recombination are now known in bacteria, which do not involve karyogamy and meiosis.

Heterokaryon – Wikipedia

Retrieved December 31, from Encyclopedia. Korf and Hartman recommended that the terms homothallism and heterothallism should be abandoned. Diploid heterozygous nuclei are formed very rarely at a frequency of one in a million.

Nonself recognition and heterokaryon incompatibility in filamentous fungi. This is because of the recombination that occurred during the mitotic crossing over. Whether nuclei migrate from one thallus to another is a debated point but the hyphae having nuclei of both parents arise at the point of fusion.

Fungi: Heterothallism, Heterokaryosis and Parasexuality | Biology

Nuclear fusion in somatic heterokaryotic hyphae was first noted by Roper in Aspergillus nidulans. Then, copy and paste the text into your bibliography or works cited list. In some bipolar species the two nuclei, which should give rise to hyphae of two mating types, are contained in the same spore.