Hypervariable region
Encyclopedia
A hypervariable region is a location within nuclear DNA
or the D-loop
of mitochondrial DNA
in which base pair
s of nucleotide
s repeat (in the case of nuclear DNA) or have substitutions (in the case of mitochondrial DNA). Changes or repeats in the hypervariable region are highly polymorphic
.
ing. HVR1 is considered a "low resolution" region and HVR2 is considered a "high resolution" region. Getting HVR1 and HVR2 DNA tests can help determine one's haplogroup. HVR1 locations are numbered 16001-16568. HVR2 locations are numbered 001-574.
In some bony fishes, for example certain Protacanthopterygii
and Gadidae
, the mitochondrial control region
evolves remarkably slowly. Even functional mitochondrial gene
s accumulate mutations faster and more freely. It is not known whether such hypovariable control regions are more widespread. In the Ayu
(Plecoglossus altivelis), an East Asia
n protacanthopterygian, control region mutation
rate is not markedly lowered, but sequence differences between subspecies
are far lower in the control region than elsewhere. This phenomenon completely defies explanation at present.
and heavy chain
s. They also contribute to the specificity of each antibody. In a variable region, the 3 HV segments of each heavy or light chain fold together at the N-terminus to form an antigen binding pocket.
Nuclear DNA
Nuclear DNA, nuclear deoxyribonucleic acid , is DNA contained within a nucleus of eukaryotic organisms. In mammals and vertebrates, nuclear DNA encodes more of the genome than the mitochondrial DNA and is composed of information inherited from two parents, one male, and one female, rather than...
or the D-loop
D-loop
In molecular biology, a displacement loop or D-loop is a DNA structure where the two strands of a double-stranded DNA molecule are separated for a stretch and held apart by a third strand of DNA. The third strand has a base sequence which is complementary to one of the main strands and pairs with...
of mitochondrial DNA
Mitochondrial DNA
Mitochondrial DNA is the DNA located in organelles called mitochondria, structures within eukaryotic cells that convert the chemical energy from food into a form that cells can use, adenosine triphosphate...
in which base pair
Base pair
In molecular biology and genetics, the linking between two nitrogenous bases on opposite complementary DNA or certain types of RNA strands that are connected via hydrogen bonds is called a base pair...
s of nucleotide
Nucleotide
Nucleotides are molecules that, when joined together, make up the structural units of RNA and DNA. In addition, nucleotides participate in cellular signaling , and are incorporated into important cofactors of enzymatic reactions...
s repeat (in the case of nuclear DNA) or have substitutions (in the case of mitochondrial DNA). Changes or repeats in the hypervariable region are highly polymorphic
Polymorphism (biology)
Polymorphism in biology occurs when two or more clearly different phenotypes exist in the same population of a species — in other words, the occurrence of more than one form or morph...
.
Mitochondrial
There are two mitochondrial hypervariable regions used in human mitochondrial genealogical DNA testGenealogical DNA test
A genealogical DNA test examines the nucleotides at specific locations on a person's DNA for genetic genealogy purposes. The test results are not meant to have any informative medical value and do not determine specific genetic diseases or disorders ; they are intended only to give genealogical...
ing. HVR1 is considered a "low resolution" region and HVR2 is considered a "high resolution" region. Getting HVR1 and HVR2 DNA tests can help determine one's haplogroup. HVR1 locations are numbered 16001-16568. HVR2 locations are numbered 001-574.
In some bony fishes, for example certain Protacanthopterygii
Protacanthopterygii
Protacanthopterygii is a ray-finned fish taxon ranked as a superorder of the infraclass Teleostei. They inhabit both marine and freshwater habitat...
and Gadidae
Gadidae
Gadidae is a family of marine fish, included in the order Gadiformes. It includes the cod, haddock, whiting, and pollock.Most species of gadid are found in temperate waters of the northern hemisphere, although there are some exceptions. They are generally medium sized fish, and are distinguished...
, the mitochondrial control region
MtDNA control region
The mtDNA control region is an area of the mitochondrial genome which is non-coding DNA. It is the most polymorphic region of the human mtDNA genome, with polymorphism concentrated in hypervariable regions. The average nucleotide diversity in these regions is 1.7%...
evolves remarkably slowly. Even functional mitochondrial gene
Gene
A gene is a molecular unit of heredity of a living organism. It is a name given to some stretches of DNA and RNA that code for a type of protein or for an RNA chain that has a function in the organism. Living beings depend on genes, as they specify all proteins and functional RNA chains...
s accumulate mutations faster and more freely. It is not known whether such hypovariable control regions are more widespread. In the Ayu
Ayu
The or sweetfish, Plecoglossus altivelis, is an amphidromous fish, the only species in the genus Plecoglossus and in family Plecoglossidae. It is a relative of the smelts and is placed in the order Osmeriformes...
(Plecoglossus altivelis), an East Asia
East Asia
East Asia or Eastern Asia is a subregion of Asia that can be defined in either geographical or cultural terms...
n protacanthopterygian, control region mutation
Mutation
In molecular biology and genetics, mutations are changes in a genomic sequence: the DNA sequence of a cell's genome or the DNA or RNA sequence of a virus. They can be defined as sudden and spontaneous changes in the cell. Mutations are caused by radiation, viruses, transposons and mutagenic...
rate is not markedly lowered, but sequence differences between subspecies
Subspecies
Subspecies in biological classification, is either a taxonomic rank subordinate to species, ora taxonomic unit in that rank . A subspecies cannot be recognized in isolation: a species will either be recognized as having no subspecies at all or two or more, never just one...
are far lower in the control region than elsewhere. This phenomenon completely defies explanation at present.
Antibodies
In antibodies, hypervariable regions form the antigen-binding site and are found on both lightImmunoglobulin light chain
]The immunoglobulin light chain is the small polypeptide subunit of an antibody .A typical antibody is composed of two immunoglobulin heavy chains and two Ig light chains.-In humans:...
and heavy chain
Heavy chain
]The immunoglobulin heavy chain is the large polypeptide subunit of an antibody .A typical antibody is composed of two immunoglobulin heavy chains and two Ig light chains. Several different types of heavy chain exist that define the class or isotype of an antibody. These heavy chain types vary...
s. They also contribute to the specificity of each antibody. In a variable region, the 3 HV segments of each heavy or light chain fold together at the N-terminus to form an antigen binding pocket.
See also
- Cambridge Reference SequenceCambridge Reference SequenceThe Cambridge Reference Sequence for human mitochondrial DNA was first published in 1981 leading to the initiation of the human genome project.A group under Dr...
- Genealogical DNA testGenealogical DNA testA genealogical DNA test examines the nucleotides at specific locations on a person's DNA for genetic genealogy purposes. The test results are not meant to have any informative medical value and do not determine specific genetic diseases or disorders ; they are intended only to give genealogical...
- Human mitochondrial DNA haplogroup
- mtDNA control regionMtDNA control regionThe mtDNA control region is an area of the mitochondrial genome which is non-coding DNA. It is the most polymorphic region of the human mtDNA genome, with polymorphism concentrated in hypervariable regions. The average nucleotide diversity in these regions is 1.7%...