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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Thus four types of spores AB, Ab, aB and ab are formed which give rise to four types of thalli. Only those thalli that have nuclei carrying opposite genes for both the factors can mate.

During meiosis, the two chromosomes, containing the alleles A and a are separated in the haploid spores germ spores, ascospores, or basidiospores. Heterothallism in Fungi 2. Blakeslee coined the terms homothallism and heterothallism to explain this phenomenon. Cite this article Pick a style below, and copy the text for your bibliography. The sexually-undifferentiated fungi e.

In such hyphae, five types of nuclei are present- 2 types of haploid nuclei, their two types of homozygous diploids, and the one type of heterozygous diploids.

However, hegerokaryosis crossing over does not take place, only two types of spores AB and ab or Ab and aB are formed and only two types of thalli are produced. These can also be homo or heterothallic.



Heterokaryosis can lead to individuals that have different nuclei in different parts of their mycelium, although in ascomycetes, particularly in ” Neurospora “, nuclei have been shown to flow and mix throughout the mycelium.

From Wikipedia, the free encyclopedia. During mitosis of the diploid nucleus, the chromatids fail to separate non-disjunction in the anaphase stage. This type of heterothallism is governed by two pairs of compatibility factors Aa and Bb, located at different chromosomes, which segregate independently during meiosis.

Heterokaryosis is most common in fungi, but also occurs in slime molds.

Print this article Print heterokaryosus entries for this topic Cite this article. The haplodization occurs not by a reduction division meiosisbut by aneuploidy, a phenomenon in which chromosomes are lost during mitotic divisions. This situation is termed secondary homothallism.

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Sexually undifferentiated- The male and female sex organs are morphologically similar and, therefore, indistinguishable. However, mitotic crossing over was discovered in by Stern in Drosophila. Both species lack sexual reproduction. Heterokaryosis is often accompanied by parasexual cycle.

This can occur naturally, such as in the mycelium of fungi during sexual reproduction, or artificially as formed by the experimental fusion of two genetically different cells, as e.


Heterokaryons show dominance and, thus, resemble diploids in many respects. In some bipolar species the two nuclei, which should give rise to hyphae of two mating types, are contained in the same spore.

heterokaryosis |

This is a question and answer forum for students, teachers and general visitors for exchanging articles, answers and notes. Heterokaryosis in Fungi 3. The deficient aneuploid nucleus 2n — 1 may lose more chromosomes in the successive mitotic division and finally reduce to haploid state n. In this case, heterothallism is made obligatory because the opposite and morphologically distinct sex organs are formed only on different thalli. Both exist in a single cell at the same time and carry out different functions with distinct cytological and biochemical properties.

Here’s how it works: Both of these diseases result in problems in mucopolysaccharide metabolism. When genetically divergent nuclei come together in the plasmodium form, cheaters have been shown to emerge.

If crossing over occurs between the mating type loci, four types of segregations AB, Ab, aB, ab are possible depending on the chromosomal arrangement. They heherokaryosis this parasexual cycle.