Lineage (genetic)
Encyclopedia
A genetic lineage is a series of mutations which connect an ancestral genetic type (allele
, haplotype
, or haplogroup
) to derivative type. In cases where the genetic tree is very bushy the order of mutations in the lineage is mostly known, examples are the order of mutations between E1b1b and E1b1b1a1a for the human Y-chromosome. In other instances the order of mutations may not be known, an example is the sequence of mutations between the L0/L1 split
for human mitochondrial DNA and the basal L0
or L1
nodes.
A genetic lineage can be contrasted with an evolutionary lineage
in that a genetic lineage applies to a locus. An example of the difference is that ancient African ape evolved into proto-gorilla and a chimpanzee-human ancestor, which further evolved into chimps and humans. While most human lineages coalesce
with chimpanzee lineages, which then converge with gorilla lineages, a few human lineages coalesce with gorilla lineages and then converge with chimpanzee lineages (or chimpanzee lineages that coalesce with gorilla lineages and then converge with human lineages). This occurs because the speciation
that marks evolutionary lineages occur as non-discrete events that are composed of 10s to 10000s of individuals in each developing taxa. This allows many variant lineages to be passed millions of years (See 2N-rule; 2 * 20 year/generations * 10,000 inds * ploidy) allows multiple deeply rooted lineages to be passed millions of years, over 2 or more speciation events. Such lineages may randomly undergo fixation
at any time.
for L1.
Allele
An allele is one of two or more forms of a gene or a genetic locus . "Allel" is an abbreviation of allelomorph. Sometimes, different alleles can result in different observable phenotypic traits, such as different pigmentation...
, haplotype
Haplotype
A haplotype in genetics is a combination of alleles at adjacent locations on the chromosome that are transmitted together...
, or haplogroup
Haplogroup
In the study of molecular evolution, a haplogroup is a group of similar haplotypes that share a common ancestor having the same single nucleotide polymorphism mutation in both haplotypes. Because a haplogroup consists of similar haplotypes, this is what makes it possible to predict a haplogroup...
) to derivative type. In cases where the genetic tree is very bushy the order of mutations in the lineage is mostly known, examples are the order of mutations between E1b1b and E1b1b1a1a for the human Y-chromosome. In other instances the order of mutations may not be known, an example is the sequence of mutations between the L0/L1 split
Mitochondrial Eve
In the field of human genetics, Mitochondrial Eve refers to the matrilineal "MRCA" . In other words, she was the woman from whom all living humans today descend, on their mother's side, and through the mothers of those mothers and so on, back until all lines converge on one person...
for human mitochondrial DNA and the basal L0
Haplogroup L0 (mtDNA)
-Distribution:It is found most commonly in the Sub-Saharan Africa. It reaches its highest frequency in the Khoisan people at 73%. Some of the higher frequencies are: Namibia 79%, South Africa 83% and Botswana 100%....
or L1
Haplogroup L1 (mtDNA)
In human mitochondrial genetics, Haplogroup L1 is a human mitochondrial DNA haplogroup common in Central and West Africa.-Origin:Haplogroup L1 is believed to have appeared approximately 110,000 to 170,000 years ago...
nodes.
A genetic lineage can be contrasted with an evolutionary lineage
Lineage (evolution)
An evolutionary lineage is a sequence of species, that form a line of descent, each new species the direct result of speciation from an immediate ancestral species. Lineages are subsets of the evolutionary tree of life. Lineages are often determined by the techniques of molecular systematics.-...
in that a genetic lineage applies to a locus. An example of the difference is that ancient African ape evolved into proto-gorilla and a chimpanzee-human ancestor, which further evolved into chimps and humans. While most human lineages coalesce
Coalescence
Coalescence may refer to:* Coalescence , the merging of genetic lineages backwards time to a most recent common ancestor* Coalescence , the merging of two or more phonological segments into one...
with chimpanzee lineages, which then converge with gorilla lineages, a few human lineages coalesce with gorilla lineages and then converge with chimpanzee lineages (or chimpanzee lineages that coalesce with gorilla lineages and then converge with human lineages). This occurs because the speciation
Speciation
Speciation is the evolutionary process by which new biological species arise. The biologist Orator F. Cook seems to have been the first to coin the term 'speciation' for the splitting of lineages or 'cladogenesis,' as opposed to 'anagenesis' or 'phyletic evolution' occurring within lineages...
that marks evolutionary lineages occur as non-discrete events that are composed of 10s to 10000s of individuals in each developing taxa. This allows many variant lineages to be passed millions of years (See 2N-rule; 2 * 20 year/generations * 10,000 inds * ploidy) allows multiple deeply rooted lineages to be passed millions of years, over 2 or more speciation events. Such lineages may randomly undergo fixation
Fixation (population genetics)
In population genetics, fixation is the change in a gene pool from a situation where there exist at least two variants of a particular gene to a situation where only one of the alleles remains...
at any time.
Basal lineage
In genetics a basal lineage is a genetic lineage that connects a variant allele (type) possessed by a more common ancestor that evolves into two descendant variants possessed by a branch ancestor. An example of a basal lineage is the lineage between mitochondrial 'Eve' and L0 or L1. Basal lineages may have types that are no longer represented in the extant population, only being defined by derivative types such as CRSCambridge Reference Sequence
The 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...
for L1.