DNA in Amy Mihaljevic Jonbenet same killer linkage theory

In the mid-2000s, improved forensic technology detected DNA among the evidence found with Amy's body. But it's not nuclear DNA, the kind you can enter into a national database. It's mitochondrial DNA, shorter strands that can only be compared directly to another person's sample. Investigators began collecting DNA from suspects, hoping for a match, but so far, none has been found.

wikipedia wrote:
Unlike nuclear DNA, which is inherited from both parents and in which genes are rearranged in the process of recombination, there is usually no change in mtDNA from parent to offspring. Although mtDNA also recombines, it does so with copies of itself within the same mitochondrion. Because of this and because the mutation rate of animal mtDNA is higher than that of nuclear DNA,[33] mtDNA is a powerful tool for tracking ancestry through females (matrilineage) and has been used in this role to track the ancestry of many species back hundreds of generations.

The low effective population size and rapid mutation rate (in animals) makes mtDNA useful for assessing genetic relationships of individuals or groups within a species and also for identifying and quantifying the phylogeny (evolutionary relationships; see phylogenetics) among different species, provided they are not too distantly related. To do this, biologists determine and then compare the mtDNA sequences from different individuals or species. Data from the comparisons is used to construct a network of relationships among the sequences, which provides an estimate of the relationships among the individuals or species from which the mtDNAs were taken. This approach has limits that are imposed by the rate of mtDNA sequence change. In animals, the high mutation rate makes mtDNA most useful for comparisons of individuals within species and for comparisons of species that are closely or moderately-closely related, among which the number of sequence differences can be easily counted. As the species become more distantly related, the number of sequence differences becomes very large; changes begin to accumulate on changes until an accurate count becomes impossible.

Mitochondrial DNA was admitted into evidence for the first time ever in 1996 during State of Tennessee v. Paul Ware.[34]

Mitochondrial DNA was first admitted into evidence in California in the successful prosecution of David Westerfield for the 2002 kidnapping and murder of 7-year-old Danielle van Dam in San Diego: it was used for both human and dog identification.[35] This was the first trial in the U.S. to admit canine DNA.[36] Human mitochondrial genetics is the study of the genetics of human mitochondrial DNA (the DNA contained in human mitochondria). 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.

Mitochondrial DNA (mtDNA) is not transmitted through nuclear DNA (nDNA). In humans, as in most multicellular organisms, mitochondrial DNA is inherited only from the mother's ovum. There are theories, however, that paternal mtDNA transmission in humans can occur under certain circumstances.[1]

Mitochondrial inheritance is therefore non-Mendelian, as Mendelian inheritance presumes that half the genetic material of a fertilized egg (zygote) derives from each parent.

wiki wrote:
Later developments

In December 2003, forensic investigators extracted enough material from a mixed blood sample found on JonBenét's underwear to establish a DNA profile.[22] The DNA belongs to an unknown male. The DNA was submitted to the FBI's Combined DNA Index System (CODIS), a database containing more than 1.6 million DNA profiles, mainly from convicted felons. The sample has yet to find a match in the database, although it continues to be checked for partial matches on a weekly basis, as are all unmatched samples.