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Scientists sort mitochondrial DNA results into more or less related groups, with more or less recent common ancestors. This leads to the construction of a DNA family tree where the branches are in biological terms clades , and the common ancestors such as Mitochondrial Eve sit at branching points in this tree.
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 ]
[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]
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 ]
The MT-TK gene is located on the p arm of the mitochondrial DNA at position 12 and it spans 70 base pairs. [2] The structure of a tRNA molecule is a distinctive folded structure which contains three hairpin loops and resembles a three-leafed clover .
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.
The mtDNA control region is an area of the mitochondrial genome which is non-coding DNA. This region controls RNA and DNA synthesis. [1] It is the most polymorphic region of the human mtDNA genome, [2] with polymorphism concentrated in hypervariable regions. The average nucleotide diversity in these regions is 1.7%. [3]