Allozymes may result from point mutations or from insertion-deletion ( indel ) events that affect the DNA coding sequence of the gene.

Perhaps the " high-water mark " of phenetics were the DNA-DNA hybridization studies by Charles G. Sibley, Jon E. Ahlquist and Burt L. Monroe Jr., from which resulted the 1990 Sibley-Ahlquist taxonomy for birds.

These base pairs have a higher thermal stability ( melting point, see also DNA-DNA hybridization ) than adenine-thymine, a property that might convey, among organisms living in high-temperature environments, a selective advantage on variants enriched in GC content.

The use of techniques such as DNA-DNA hybridization to study evolutionary relationships was pioneered by Charles Sibley and Jon Edward Ahlquist resulting in what is called the Sibley-Ahlquist taxonomy.

However, the resolution of the DNA-DNA hybridization technique used by Sibley & Ahlquist was not sufficient to properly resolve the relationships in this group, and indeed it appears as if the Charadriiformes consititute a single large and very distinctive lineage of modern birds of their own.

Following the development of research techniques in molecular biology in the late 20th century, in particular methods for studying DNA-DNA hybridization, a great deal of new information has surfaced, much of it suggesting that many birds, although looking very different from one another, are in fact more closely related than was previously thought.

Molecular studies such as DNA-DNA hybridization ( Sibley & Ahlquist, 1990 ) and sequence analyses fail to resolve the relationships of grebes properly due to insufficient resolution in the former and long-branch attraction in the latter.

* ( 1988 ): A classification of the living birds of the world based on DNA-DNA hybridization studies.

In the period of 1974 – 1986, DNA-DNA hybridization was the dominant technique.

In the period of 1974 – 1986, DNA-DNA hybridization was the dominant technique.

This was confirmed by Sibley & Ahlquist ( 1990 ) based on DNA-DNA hybridization and subsequently by Paton et al.

Sibley and Ahlquist furthermore removed button-quails ( Turnicidae ) from the Gruifomes based on large DNA-DNA hybridization distances to other supposed Gruiformes.

It is based on DNA-DNA hybridization studies conducted in the late 1970s and throughout the 1980s.

DNA-DNA hybridization is among a class of comparative techniques in molecular biology that produce distance data ( versus character data ) and that can be analyzed to produce phylogenetic reconstructions only using phenetic tree-building algorithms.

In DNA-DNA hybridization, the percent similarity of DNA between two species is estimated by the reduction in hydrogen bonding between nucleotides of imperfectly complemented heteroduplex DNA ( i. e., double stranded DNAs that are experimentally produced from single strands of two different species ), compared with perfectly matched homoduplex DNA ( both strands of DNA from the same species ).

However the classification study did not employ modern cladistic methods, as it relies strictly on DNA-DNA hybridization as the sole measure of similarity.

Initial mtDNA cytochrome b sequence analysis ( Mariaux & Braun 1996 ) agreed with earlier morphological ( Cracraft 1981 ) and DNA-DNA hybridization ( Sibley & Ahlquist 1990 ) studies insofar as that the oilbird and the frogmouths seemed rather distinct.

The swallows and martins are morphologically unique within the passerines, but the use of DNA-DNA hybridization studies has suggested relationships with the Old World warblers ( a large wastebin taxon that has recently been split into several new families ), the white-eyes and the tits.

This makes the expanded Sturnidae a rather noninformative group and is probably due to the methodological drawbacks of their DNA-DNA hybridization technique.

Estimate of relationships among subgenera based on DNA-DNA hybridization.

DNA-DNA hybridization and RAG-1 sequence data places it as a wader related to the jacanas ( Sibley & Ahlquist 1990, Paton et al.

The Sibley-Ahlquist taxonomy elevated them to ordinal status as the Turniciformes and basal to other Neoaves either because their accelerated rate of molecular evolution exceeded the limits of sensitivity of DNA-DNA hybridization or because the authors did not perform the appropriate pairwise comparisons or both.

Morphological, DNA-DNA hybridization and sequence data indicate that turnicids correctly belong to the shorebirds ( Charadriiformes ).

However, the grouping of Sibley & Monroe ( besides leaving the subfamily rank vacant ) is overly coarse due to methodological drawbacks of their DNA-DNA hybridization technique and most of their proposed revisions of taxonomic rank have not been accepted ( see for example Ciconiiformes ).

* Sheldon, Frederick H .; McCracken, Kevin G. & Stuebing, Keeley D. ( 1995 ): Phylogenetic relationships of the zigzag heron ( Zebrilus undulatus ) and white-crested bittern ( Tigriornis leucolophus ) estimated by DNA-DNA hybridization.

DNA-DNA hybridization generally refers to a molecular biology technique that measures the degree of genetic similarity between pools of DNA sequences.

More recently published phylogenetic reconstructions based on cladistic and maximum likelihood analyses of DNA sequences lend credence to some of the DNA-DNA hybridization-based taxonomy, e. g. the recognition of palaeognathous birds as monophyletic and sister to all others.

DNA-DNA hybridization placed the Olive Warbler as an early branch of the finch clade ( which included the finches, cardinals and Hawaiian honeycreepers ) and the New World sparrow clade ( which includes the tanagers, icterids and New world warblers ), and a 1998 study of mitochondrial DNA confirmed its status as being far removed from the New world warblers.

These conclusions have demonstrated good statistical support using nuclear and mitochondrial DNA, as well as DNA-DNA hybridization.

The removal of the RNA primer allows DNA ligase to ligate the DNA-DNA nick between the new fragment and the previous strand.

Since then, the same principle has been adapted to describe many alternative methods including some that detect protein – DNA interactions, DNA-DNA interactions and use Escherichia coli instead of yeast.

Sim4 is a nucleotide sequence alignment program akin to BLAST but specifically tailored to DNA to cDNA / EST ( Expressed Sequence Tag ) alignment ( as opposed to DNA-DNA or protein-protein alignment ).

The Sibley-Ahlquist taxonomy of birds, based upon DNA-DNA hybridization, suggested that the Limpkin's closest relatives were the Heliornithidae finfoots, and Sibley and Monroe even placed the species in that family in 1990.

With the new insights generated by the DNA-DNA hybridisation studies of Sibley and his co-workers toward the end of the 20th century, however, it became clear that these apparently unrelated birds were all descended from a common ancestor: the same crow-like ancestor that gave rise to the drongos.

Charles Sibley and Jon Ahlquist, pioneers of the technique, used DNA-DNA hybridization to examine the phylogenetic relationships of avians ( the Sibley-Ahlquist taxonomy ) and primates.

The model is used in a variety of biochemical situations other than enzyme-substrate interaction, including antigen-antibody binding, DNA-DNA hybridization and protein-protein interaction.

Following the development of research techniques in molecular biology in the late 20th century, in particular methods for studying DNA-DNA hybridisation, a great deal of new information has surfaced, much of it suggesting that many birds, although looking very different from one another, are in fact more closely related than was previously thought.

That move was supported by chromosome and DNA-DNA hybridisation studies, but challenged on the grounds that all three groups are monophyletic with respect to the other Coraciiformes.

In their pioneering DNA-DNA hybridisation work, Sibley and Ahlquist found that the genetic difference between the eared-nightjars and the typical nightjars was, in fact, greater than that between the typical nightjars and the nighthawks of the New World.

An older and superseded approach was to determine the divergences between the genotypes of individuals by DNA-DNA hybridisation.

Sibley & Ahlquist ( 1990 ) united the " Old World warblers " with the babblers and other taxa in a superfamily Sylvioidea as a result of DNA-DNA hybridisation studies.

Sibley and Ahlquist's landmark DNA-DNA hybridisation studies ( see Sibley-Ahlquist taxonomy ) led to them placing the families traditionally contained within the Pelecaniformes together with the grebes, cormorants, ibises and spoonbills, New World vultures, storks, penguins, albatrosses, petrels, and loons together as a sub-group within a greatly expanded order Ciconiiformes, a radical move which by now has been all but rejected: their " Ciconiiformes " merely assembled all early advanced land-and seabirds for which their research technique delivered insufficient phylogenetic resolution.