Uniparental inheritance

Last updated December 16, 2020

Uniparental inheritance is a non-mendelian form of inheritance that consists of the transmission of genotypes from one parental type to all progeny. That is, all the genes in offspring will originate from only the mother or only the father. This phenomenon is most commonly observed in eukaryotic organelles such as mitochondria and chloroplasts. This is because such organelles contain their own DNA and are capable of independent mitotic replication that does not endure crossing over with the DNA from another parental type. 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. Furthermore, there is evidence that the form of organelle inheritance varied frequently over time. Uniparental inheritance can be divided into multiple subtypes based on the pathway of inheritance.^[1]^[2]

Examples

Organelles

Although most of the eukaryotic sub-cellular parts do not have their own DNA nor are capable of replication independent of the nucleus, there are some exceptions such as mitochondria and chloroplasts. Not only are these organelles capable of independent DNA replication, translation, and transcription, they are commonly known to inherit genes from only one parental type. In the case of mitochondria, maternal inheritance is almost the exclusive form of inheritance. Although, during egg cell fertilization, mitochondria are brought into the fertilized cell both by the egg cell and the sperm, the paternal mitochondria are usually marked with ubiquitin and are later destroyed.^[3] Even if they are not destroyed, the DNA's of different mitochondria rarely genetically recombine with one another. Thus, mitochondria in most animals are inherited from the maternal type only.

History

Like all other genetic concepts, the discovery of uniparental inheritance stems from the days of an Augustinian priest known as Gregor Johann Mendel. The soon-to-be "father of modern genetics" spent his days conducting hybridization experiments on pea plants( Pisum sativum ) in his monastery's garden. During a period of seven years (1856 to 1863), Mendel cultivated and tested some 29,000 pea plants which led to him deducing the two famous generalizations known as Mendel's Laws of Heredity. The first, the law of segregation, states that "when any individual produces gametes, the copies of a gene separate, so that each gamete receives only one copy". The second, the law of independent assortment, states that "alleles of different genes assort independently of one another during gamete formation". Although his work was published, it lay dormant until it was rediscovered in 1900 by Hugo de Vries and Carl Correns but it was not until 1909 that non-mendelian inheritance was even suggested. Carl Erich Correns and Erwin Baur, in separately conducted researches on Pelargonium and Mirabilis plants, observed a green-white variation (later found as the result of mutations in the chloroplast genome) that did not follow the Mendelian laws of inheritance. Nearly twenty years later, non-mendelian inheritance of a mitochondrial mutation was also observed and, in the sixties, it was proven that chloroplasts and mitochondria have their own DNA and that they are capable translation, transcription, and replication independent of the nucleus. Soon after, the discoveries of uniparental and doubly uniparental inheritance came.^[1]

Poky mutants of Neurospora

A well studied example of uniparental inheritance involves the poky mutants of Neurospora crassa . The original poky mutant was isolated by Mitchell and Mitchell in 1952 as a spontaneously occurring slow growing variant.^[4] In genetic crosses, the poky phenotype was found to be maternally inherited. The protoperithecial parent is regarded as the female (maternal) parent in Neurospora. When poky females were crossed to wild-type males, all progeny had the poky phenotype. When wild-type females were crossed to poky males, all progeny had the wild-type phenotype. That the poky determinant is only passed through the female line suggested that the determinant resides in the maternal cytoplasm. It was eventually shown that the primary defect in the poky mutants is a deletion in the mitochondrial DNA sequence encoding the small ribosomal RNA subunit.^[5]

Related Research Articles

An allele is one of two, or more, forms of a given gene variant. E.g. the ABO blood grouping is controlled by the ABO gene which has six common alleles. Nearly every living human's phenotype for the ABO gene is some combination of just these six alleles. An allele is one of two, or more, versions of the same gene at the same place on a chromosome. It can also refer to different sequence variations for a several-hundred base-pair or more region of the genome that codes for a protein. Alleles can come in different extremes of size. At the lowest possible size an allele can be a single nucleotide polymorphism (SNP). At the higher end, it can be up to several thousand base-pairs long. Most alleles result in little or no observable change in the function of the protein the gene codes for.

Mendelian inheritance Type of biological inheritance

Mendelian inheritance is a type of biological inheritance that follows the principles originally proposed by Gregor Mendel in 1865 and 1866, re-discovered in 1900 and popularized by William Bateson. These principles were initially controversial. When Mendel's theories were integrated with the Boveri–Sutton chromosome theory of inheritance by Thomas Hunt Morgan in 1915, they became the core of classical genetics. Ronald Fisher combined these ideas with the theory of natural selection in his 1930 book The Genetical Theory of Natural Selection, putting evolution onto a mathematical footing and forming the basis for population genetics within the modern evolutionary synthesis.

Mitochondrial DNA is the DNA located in mitochondria, cellular organelles within eukaryotic cells that convert chemical energy from food into a form that cells can use, adenosine triphosphate (ATP). Mitochondrial DNA is only a small portion of the DNA in a eukaryotic cell; most of the DNA can be found in the cell nucleus and, in plants and algae, also in plastids such as chloroplasts.

The plastid is a membrane-bound organelle found in the cells of plants, algae, and some other eukaryotic organisms. They are considered endosymbiotic Cyanobacteria, related to the Gloeomargarita. The event to permanent endosymbiosis probably occurred with a cyanobiont. Plastids were discovered and named by Ernst Haeckel, but A. F. W. Schimper was the first to provide a clear definition. Plastids are the site of manufacture and storage of important chemical compounds used by the cells of autotrophic eukaryotes. They often contain pigments used in photosynthesis, and the types of pigments in a plastid determine the cell's color. They have a common evolutionary origin and possess a double-stranded DNA molecule that is circular, like that of the circular chromosome of prokaryotic cells.

Genetic linkage is the tendency of DNA sequences that are close together on a chromosome to be inherited together during the meiosis phase of sexual reproduction. Two genetic markers that are physically near to each other are unlikely to be separated onto different chromatids during chromosomal crossover, and are therefore said to be more linked than markers that are far apart. In other words, the nearer two genes are on a chromosome, the lower the chance of recombination between them, and the more likely they are to be inherited together. Markers on different chromosomes are perfectly unlinked.

Heteroplasmy is the presence of more than one type of organellar genome within a cell or individual. It is an important factor in considering the severity of mitochondrial diseases. Because most eukaryotic cells contain many hundreds of mitochondria with hundreds of copies of mitochondrial DNA, it is common for mutations to affect only some mitochondria, leaving most unaffected.

Homoplasmy Identity of organellar DNA sequences in a cell

Homoplasmy is a term used in genetics to describe a eukaryotic cell whose copies of mitochondrial DNA are all identical. In normal and healthy tissues, all cells are homoplasmic. Homoplasmic mitochondrial DNA copies may be normal or mutated; however, most mutations are heteroplasmic. It has been discovered, though, that homoplasmic mitochondrial DNA mutations may be found in human tumors.

Human mitochondrial genetics is the study of the genetics of human mitochondrial DNA. The human mitochondrial genome is the entirety of hereditary information contained in human mitochondria. Mitochondria are small structures in cells that generate energy for the cell to use, and are hence referred to as the "powerhouses" of the cell.

Non-Mendelian inheritance is any pattern of inheritance in which traits do not segregate in accordance with Mendel's laws. These laws describe the inheritance of traits linked to single genes on chromosomes in the nucleus. In Mendelian inheritance, each parent contributes one of two possible alleles for a trait. If the genotypes of both parents in a genetic cross are known, Mendel's laws can be used to determine the distribution of phenotypes expected for the population of offspring. There are several situations in which the proportions of phenotypes observed in the progeny do not match the predicted values.

Carl Erich Correns was a German botanist and geneticist, who is notable primarily for his independent discovery of the principles of heredity, which he achieved simultaneously but independently of the botanist Hugo de Vries and for his rediscovery of Gregor Mendel's earlier paper on that subject.

Genetics, a discipline of biology, is the science of heredity and variation in living organisms.

Intragenomic conflict refers to the evolutionary phenomenon where genes have phenotypic effects that promote their own transmission in detriment of the transmission of other genes that reside in the same genome. The selfish gene theory postulates that natural selection will increase the frequency of those genes whose phenotypic effects cause their transmission to new organisms, and most genes achieve this by cooperating with other genes in the same genome to build an organism capable of reproducing and/or helping kin to reproduce. The assumption of the prevalence of intragenomic cooperation underlies the organism-centered concept of inclusive fitness. However, conflict among genes in the same genome may arise both in events related to reproduction and altruism.

petite (ρ–) is a mutant first discovered in the yeast Saccharomyces cerevisiae. Due to the defect in the respiratory chain, 'petite' yeast are unable to grow on media containing only non-fermentable carbon sources and form small colonies when grown in the presence of fermentable carbon sources. The petite phenotype can be caused by the absence of, or mutations in, mitochondrial DNA, or by mutations in nuclear-encoded genes involved in oxidative phosphorylation. A neutral petite produces all wild type progeny when crossed with wild type.

A nuclear gene is a gene located in the cell nucleus of a eukaryote. The term is used to distinguish nuclear genes from the genes of the endosymbiotic organelle, that is genes in the mitochondrion, and in case of plants and algae, the chloroplast, which host their own genetic system and can produce proteins from scratch. A nuclear gene is just one of the genetic building blocks of a eukaryotic organism's entire genome.

Extrachromosomal DNA is any DNA that is found off the chromosomes, either inside or outside the nucleus of a cell. Most DNA in an individual genome is found in chromosomes contained in the nucleus. Multiple forms of extrachromosomal DNA exist and serve important biological functions, e.g. they can play a role in disease, such as ecDNA in cancer.

In genetics, paternal mtDNA transmission and paternal mtDNA inheritance refer to the incidence of mitochondrial DNA (mtDNA) being passed from a father to his offspring. Paternal mtDNA inheritance is observed in a small proportion of species; in general, mtDNA is passed unchanged from a mother to her offspring, making it an example of non-Mendelian inheritance. In contrast, mtDNA transmission from both parents occurs regularly in certain bivalves.

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.

Cytoplasmic male sterility is total or partial male sterility in plants as the result of specific nuclear and mitochondrial interactions. Male sterility is the failure of plants to produce functional anthers, pollen, or male gametes.

Organellar DNA (oDNA) is DNA contained in organelles, outside the nucleus of Eukaryotic cells.

The CoRR hypothesis states that the location of genetic information in cytoplasmic organelles permits regulation of its expression by the reduction-oxidation ("redox") state of its gene products.

References

1 2 Xu, Jianping (1 December 2005). "The inheritance of organelle genes and genomes: patterns and mechanisms". Genome. 48 (6): 951–958. doi:10.1139/g05-082.
↑ Birky, C. W. (5 December 1995). "Uniparental inheritance of mitochondrial and chloroplast genes: mechanisms and evolution". Proceedings of the National Academy of Sciences. 92 (25): 11331–11338. doi: 10.1073/pnas.92.25.11331 .
↑ Sutovsky, P.; et al. (1999). "Ubiquitin tag for sperm mitochondria". Nature . 402 (6760): 371–372. doi:10.1038/46466. PMID 10586873. Discussed in Science News.
↑ Mitchell MB, Mitchell HK (May 1952). "A Case of "Maternal" Inheritance in Neurospora Crassa". Proc. Natl. Acad. Sci. U.S.A. 38 (5): 442–9. doi:10.1073/pnas.38.5.442. PMC 1063583 . PMID 16589122.
↑ Akins RA, Lambowitz AM (June 1984). "The [poky] mutant of Neurospora contains a 4-base-pair deletion at the 5' end of the mitochondrial small rRNA". Proc. Natl. Acad. Sci. U.S.A. 81 (12): 3791–5. doi:10.1073/pnas.81.12.3791. PMC 345306 . PMID 6233613.

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[Xu2005-1] 1 2 Xu, Jianping (1 December 2005). "The inheritance of organelle genes and genomes: patterns and mechanisms". Genome. 48 (6): 951–958. doi:10.1139/g05-082.

[2] Birky, C. W. (5 December 1995). "Uniparental inheritance of mitochondrial and chloroplast genes: mechanisms and evolution". Proceedings of the National Academy of Sciences. 92 (25): 11331–11338. doi: 10.1073/pnas.92.25.11331 .

[3] Sutovsky, P.; et al. (1999). "Ubiquitin tag for sperm mitochondria". Nature . 402 (6760): 371–372. doi:10.1038/46466. PMID 10586873. Discussed in Science News.

[pmid16589122-4] Mitchell MB, Mitchell HK (May 1952). "A Case of "Maternal" Inheritance in Neurospora Crassa". Proc. Natl. Acad. Sci. U.S.A. 38 (5): 442–9. doi:10.1073/pnas.38.5.442. PMC 1063583 . PMID 16589122.

[pmid6233613-5] Akins RA, Lambowitz AM (June 1984). "The [poky] mutant of Neurospora contains a 4-base-pair deletion at the 5' end of the mitochondrial small rRNA". Proc. Natl. Acad. Sci. U.S.A. 81 (12): 3791–5. doi:10.1073/pnas.81.12.3791. PMC 345306 . PMID 6233613.

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