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In genetics, a maternal effect occurs when the phenotype of an organism is determined by the genotype of its mother. [1] For example, if a mutation is maternal effect recessive, then a female homozygous for the mutation may appear phenotypically normal, however her offspring will show the mutant phenotype, even if they are heterozygous for the mutation.
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]
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.
Paternal leakage – Although mtDNA is thought to be exclusively maternally inherited, paternal inheritance exists in a low frequency of 10 −4 relative to maternal inheritance in mice. [10] Hence, selection can act on male-specific deleterious mutations when they are paternally inherited, decreasing their frequency.
Paternal stress is an important factor in the determination of inheritance of genes as well as maternal stress inheritance. Factors such as environment and experiences can alter the epigenetic of paternal genes as well as in sperm. Epigenetic changes to the DNA in sperm ("epigenetic tags") prior to conception can be passed to offspring.
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]
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]
The cell-intrinsic properties arise from a cleavage of a cell with asymmetrically expressed maternal cytoplasmic determinants (proteins, small regulatory RNAs and mRNA). Thus, the fate of the cell depends on factors secreted into its cytoplasm during cleavage.