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Sexual reproduction, where offspring result from the fusion of gametes from two parents, is the most common form of biparental inheritance. While less common, cases of biparental inheritance in extranuclear genes have been documented, such as biparental inheritance of mitochondrial DNA, or chloroplast DNA in plants. [1]
[2] [3] [4] In testing 172 sheep, "The Mitochondrial DNA from three lambs in two half-sib families were found to show paternal inheritance." [5] An instance of paternal leakage resulted in a study on chickens. [6] There has been evidences that paternal leakage is an integral part of mitochondrial inheritance of Drosophila simulans. [7]
Mitochondrial DNA is a small portion of the DNA contained in a eukaryotic cell; most of the DNA is in the cell nucleus, and, in plants and algae, the DNA also is found in plastids, such as chloroplasts. [3] Human mitochondrial DNA was the first significant part of the human genome to be sequenced. [4]
We previously thought mitochondrial DNA could only be passed on by mothers. Skip to main content. 24/7 Help. For premium support please call: 800-290-4726 more ways to reach us ...
In humans, mitochondrial DNA (mtDNA) forms closed circular molecules that contain 16,569 [4] [5] DNA base pairs, [6] with each such molecule normally containing a full set of the mitochondrial genes. Each human mitochondrion contains, on average, approximately 5 such mtDNA molecules, with the quantity ranging between 1 and 15. [ 6 ]
Mitochondria with their mitochondrial DNA are already present in the egg cell before it gets fertilized by a sperm. In many cases of fertilization, the head of the sperm enters the egg cell; leaving its middle part, with its mitochondria, behind. The mitochondrial DNA of the sperm often remains outside the zygote and gets excluded from inheritance.
Branches are identified by one or more unique markers which give a mitochondrial "DNA signature" or "haplotype" (e.g. the CRS is a haplotype). Each marker is a DNA base-pair that has resulted from an SNP mutation. Scientists sort mitochondrial DNA results into more or less related groups, with more or less recent common ancestors.
Mitochondrial DNA usually has 16,569 base pairs (the number can vary slightly depending on addition or deletion mutations) [24] and is much smaller than the human genome DNA which has 3.2 billion base pairs. Mitochondrial DNA is transmitted from mother to child, as it is contained in the egg cell.