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Extranuclear inheritance or cytoplasmic inheritance is the transmission of genes that occur outside the nucleus. It is found in most eukaryotes and is commonly known to occur in cytoplasmic organelles such as mitochondria and chloroplasts or from cellular parasites like viruses or bacteria. [1] [2] [3]
Extranuclear inheritance (also known as cytoplasmic inheritance) is a form of non-Mendelian inheritance also first discovered by Carl Correns in 1908. [9] While working with Mirabilis jalapa, Correns observed that leaf colour was dependent only on the genotype of the maternal parent.
Mutations in mtDNA or other cytoplasmic DNA will also be inherited from the mother. This uniparental inheritance is an example of non-Mendelian inheritance. Plants also show uniparental mtDNA inheritance. Most plants inherit mtDNA maternally with one noted exception being the redwood Sequoia sempervirens that inherit mtDNA paternally. [46]
Although uniparental inheritance is the most common form of inheritance in organelles, there is increased evidence of diversity. Some studies found doubly uniparental inheritance (DUI) and biparental transmission to exist in cells. Evidence suggests that even when there is biparental inheritance, crossing-over doesn't always occur.
One of the most noteworthy aspects of plasmagenes is their involvement in non-Mendelian inheritance patterns. Unlike nuclear genes, which are inherited from both parents, plasmagenes are typically inherited maternally. This occurs because cytoplasmic organelles, like mitochondria, are transferred primarily through the egg cell during fertilization.
Uniparental inheritance refers to the fact that, in most organisms, many offspring inherit organelle genes from only one parent. However, this is not a general law. Many organisms that have the ability to differentiate maternal and paternal sexes will produce offspring with a mixture of maternal, paternal, and biparental mitochondrial DNA.
Petite mutants show extranuclear inheritance.The inheritance pattern varying with the type of petite involved. Segregational petites (pet–): mutants are created by nuclear mutations and exhibit Mendelian 1:1 segregation. [9] Neutral petites (rho–N): Neutral petite when crossed to wild-type, all offspring are wild-type. It has inherited ...
Since nuclear and cytoplasmic genes usually have different modes of transmission, intragenomic conflicts between them may arise. [18] Mitochondria and chloroplasts are two examples of sets of cytoplasmic genes that commonly have exclusive maternal inheritance, similar to endosymbiont parasites in arthropods, like Wolbachia. [19]