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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]
Mechanisms for this include simple dilution (an egg contains on average 200,000 mtDNA molecules, whereas a healthy human sperm has been reported to contain on average 5 molecules), [43] [44] degradation of sperm mtDNA in the male genital tract and in the fertilized egg; and, at least in a few organisms, failure of sperm mtDNA to enter the egg.
Each human cell contains approximately 100 mitochondria, giving a total number of mtDNA molecules per human cell of approximately 500. [35] However, the amount of mitochondria per cell also varies by cell type, and an egg cell can contain 100,000 mitochondria, corresponding to up to 1,500,000 copies of the mitochondrial genome (constituting up ...
[13] [14] Mitochondria have been implicated in several human disorders and conditions, such as mitochondrial diseases, [15] cardiac dysfunction, [16] heart failure [17] and autism. [18] The number of mitochondria in a cell can vary widely by organism, tissue, and cell type.
The number of mtDNA molecules per mitochondrion varies from species to species, as well as between cells with different energy demands. For example, muscle and liver cells contain more copies of mtDNA per mitochondrion than blood and skin cells do. [ 23 ]
Human mtDNA codes for 13 proteins, most of which are involved in oxidative phosphorylation (OXPHOS). The nuclear genome encodes the remaining mitochondrial proteins, which are then transported into the mitochondria. [2] The genomes of these organelles have become far smaller than those of their free-living predecessors.
Pearson syndrome is a mitochondrial disease caused by a deletion in mitochondrial DNA (mtDNA). [3] An mtDNA is genetic material contained in the cellular organelle called the mitochondria. Depending on the tissue type, each cell contains hundreds to thousands of mitochondria. There are 2–10 mtDNA molecules in each mitochondrion.
Macro-haplogroup L is the most basal of human mtDNA haplogroups, from which all other haplogroups descend (specifically, from haplogroup L3). It is found mostly in Africa. Haplogroup L0; L1-7 Haplogroup L1; L2-7 L3'4'6 Haplogroup L2