John A. Gifford

Bio: John A. Gifford is an academic researcher. The author has contributed to research in topics: Ancient DNA & Molecular cloning. The author has an hindex of 1, co-authored 1 publications receiving 452 citations.

Mitochondrial DNA sequences from a 7000-year old brain

Abstract: Pieces of mitochondrial DNA from a 7000-year-old human brain were amplified by the polymerase chain reaction and sequenced. Albumin and high concentrations of polymerase were required to overcome a factor in the brain extract that inhibits amplification. For this and other sources of ancient DNA, we find an extreme inverse dependence of the amplification efficiency on the length of the sequence to be amplified. This property of ancient DNA distinguishes it from modern DNA and thus provides a new criterion of authenticity for use in research on ancient DNA. The brain is from an individual recently excavated from Little Salt Spring in southwestern Florida and the anthropologically informative sequences it yielded are the first obtained from archaeologically retrieved remains. The sequences show that this ancient individual belonged to a mitochondrial lineage that is rare in the Old World and not previously known to exist among Native Americans. Our finding brings to three the number of maternal lineages known to have been involved in the prehistoric colonization of the New World.

The polymerase chain reaction. A new method of using molecular genetics for medical diagnosis.

Abstract: THE development of molecular genetics, both as a self-contained field and as a body of techniques broadly useful in biologic investigation, has had a profound influence on medical research. The beneficiaries include every discipline in basic science and, at least indirectly, most clinical and applied medical disciplines. Certain technical milestones can be identified over the past several decades that have been particularly important in the progress of the field. One is the discovery of restriction endonucleases, which together with the development of DNA ligation and transformation procedures, led to the ability to clone and thus propagate genes of any organism . . .

Identification of the remains of the Romanov family by DNA analysis

Abstract: Nine skeletons found in a shallow grave in Ekaterinburg, Russia, in July 1991, were tentatively identified by Russian forensic authorities as the remains of the last Tsar, Tsarina, three of their five children, the Royal Physician and three servants. We have performed DNA based sex testing and short tandem repeat (STR) analysis and confirm that a family group was present in the grave. Analysis of mitochondrial (mt) DNA reveals an exact sequence match between the putative Tsarina and the three children with a living maternal relative. Amplified mtDNA extracted from the remains of the putative Tsar has been cloned to demonstrate heteroplasmy at a single base within the mtDNA control region. One of these sequences matches two living maternal relatives of the Tsar. We conclude that the DNA evidence supports the hypothesis that the remains are those of the Romanov family.

Identification of the heme compound copurified with deoxyribonucleic acid (DNA) from bloodstains, a major inhibitor of polymerase chain reaction (PCR) amplification.

Abstract: The heme compound found in deoxyribonucleic acid (DNA) extracted from bloodstains, which is regarded as a major inhibitor of polymerase chain reaction (PCR), was characterized in comparison with alkaline and acid hematin, histidine and ammonia hemochromogens, and globin and serum albumin hemochromogens digested by proteinase K. Alkaline and acid hematin were almost completely removed by phenol/chloroform treatment and ethanol precipitation, so as not to be copurified with DNA from the specimens. Spectrophotometric results indicated that the contaminant was likely to be the product of proteinase K digestion of some heme-blood protein complex, which was not completely extracted by organic solvents and remained in the ethanol precipitates of DNA. The results of polyacrylamide gradient gel electrophoresis and intensity of the inhibition of PCR suggested that the ligand of the contaminant was a somewhat large molecule, resistant to the proteolysis by proteinase K. The addition of bovine serum albumin to the reaction mixture prevented the inhibition of PCR by the heme compounds, probably by binding to the heme. This showed that the inhibition was not due to the irreversible inactivation of the enzyme.

Sympatric speciation suggested by monophyly of crater lake cichlids

Abstract: THE existence of sympatric speciation—that populations diverge into species in the absence of physical or ecological barriers—is controversial1–6. The East African Great Lakes harbour hundreds of cichlid species representing only a few monophyletic lineages7,8, although palaeolimnological evidence9–11 and local restrictions on species distribution12 suggest that speciation in these lakes could have been allopatric13,14. The case for sympatry in restricted areas of Lakes Malawi and Tanganyika is stronger15–17 but not unassailable. A better case might be made for cichlid species flocks in small, ecologically monotonous crater lakes. Here we present a mitochondrial DNA analysis of cichlid species flocks endemic to two such lakes in Cameroon. The results suggest that the flocks in each lake are monophyletic: the implication being that each lake was colonized once only, the size and shape of each lake being such that subsequent diversification would have been sympatric.