In most multicellular organisms, mtDNA is inherited from the mother (maternally inherited). Mechanisms for this include simple dilution (an egg contains on average 200,000 mtDNA molecules, whereas a healthy human sperm was reported to contain on average 5 molecules, degradation of sperm mtDNA in the male genital tract, in the fertilized egg, and, at least in a few organisms, failure of sperm mtDNA to enter the egg.
In sexual reproduction, mitochondria are normally inherited exclusively from the mother; the mitochondria in mammalian sperm are usually destroyed by the egg cell after fertilization. Also, most mitochondria are present at the base of the sperm's tail, which is used for propelling the sperm cells; sometimes the tail is lost during fertilization. In 1999 it was reported that paternal sperm mitochondria (containing mtDNA) are marked with ubiquitin to select them for later destruction inside the embryo.Some invitro fertilization techniques, particularly injecting a sperm into an oocyte, may interfere with this.
In most multicellular organisms, mtDNA is inherited from the mother (maternally inherited). Mechanisms for this include simple dilution (an egg contains on average 200,000 mtDNA molecules, whereas a healthy human sperm was reported to contain on average 5 molecules, degradation of sperm mtDNA in the male genital tract, in the fertilized egg, and, at least in a few organisms, failure of sperm mtDNA to enter the egg.
In sexual reproduction, mitochondria are normally inherited exclusively from the mother; the mitochondria in mammalian sperm are usually destroyed by the egg cell after fertilization. Also, most mitochondria are present at the base of the sperm's tail, which is used for propelling the sperm cells; sometimes the tail is lost during fertilization. In 1999 it was reported that paternal sperm mitochondria (containing mtDNA) are marked with ubiquitin to select them for later destruction inside the embryo.Some invitro fertilization techniques, particularly injecting a sperm into an oocyte, may interfere with this.
As an expert in molecular biology and genetics, my extensive knowledge in the field allows me to provide a thorough understanding of the concepts mentioned in the article. The article primarily discusses mitochondrial DNA (mtDNA) inheritance in multicellular organisms, focusing on the maternally inherited nature of mtDNA and the mechanisms involved in this process.
One key concept highlighted is the phenomenon of maternal inheritance, where mtDNA is passed exclusively from the mother to her offspring. This is a well-established principle observed in most multicellular organisms. The article mentions several mechanisms contributing to maternally inherited mtDNA:
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Simple Dilution: The article notes that an egg contains, on average, 200,000 mtDNA molecules, while a healthy human sperm carries only about 5 molecules. This discrepancy in the quantity of mtDNA between eggs and sperm contributes to the predominant inheritance of maternal mtDNA.
See AlsoGenetic Genealogy -
Degradation of Sperm mtDNA: The male genital tract is identified as a site for the degradation of sperm mtDNA. This degradation process further reinforces the selective inheritance of maternal mtDNA.
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Failure of Sperm mtDNA Entry: In some organisms, the article suggests that there is a failure of sperm mtDNA to enter the egg, contributing to the maternally inherited pattern.
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Destruction of Mitochondria in Sperm: Following fertilization, the mitochondria in mammalian sperm are usually destroyed by the egg cell. This destruction ensures that only maternal mitochondria are retained in the developing embryo.
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Ubiquitin Marking: A noteworthy detail mentioned is the marking of paternal sperm mitochondria, which contain mtDNA, with ubiquitin. This ubiquitin marking serves as a tag to select these mitochondria for later destruction within the embryo.
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Mitochondrial Localization in Sperm: The article highlights that most mitochondria in sperm are located at the base of the sperm's tail, which is used for propelling the sperm cells. The loss of the tail during fertilization is also noted, indicating a potential impact on mitochondrial inheritance.
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In Vitro Fertilization (IVF) Techniques: The article suggests that certain IVF techniques, particularly the injection of sperm into an oocyte, may interfere with the typical mechanisms of mitochondrial inheritance. This interference could lead to variations in mitochondrial transmission patterns.
In summary, the article delves into the intricate details of mtDNA inheritance, shedding light on the various mechanisms and factors that contribute to the maternally inherited nature of mitochondria in most multicellular organisms. The described processes highlight the complexity and precision involved in the transmission of genetic material from one generation to the next.
