A genetic lineage includes all descendants of a given genetic sequence, typically following a new

mutation In biology, a mutation is an alteration in the nucleic acid sequence of the genome of an organism, virus, or extrachromosomal DNA. Viral genomes contain either DNA or RNA. Mutations result from errors during DNA or viral replication, ...

. It is not the same as an

allele An allele is a variant of the sequence of nucleotides at a particular location, or Locus (genetics), locus, on a DNA molecule. Alleles can differ at a single position through Single-nucleotide polymorphism, single nucleotide polymorphisms (SNP), ...

because it excludes cases where different mutations give rise to the same allele, and includes descendants that differ from the ancestor by one or more

mutations In biology, a mutation is an alteration in the nucleic acid sequence of the genome of an organism, virus, or extrachromosomal DNA. Viral genomes contain either DNA or RNA. Mutations result from errors during DNA or viral replication, mitosi ...

. The genetic sequence can be of different sizes, e.g. a single

gene In biology, the word gene has two meanings. The Mendelian gene is a basic unit of heredity. The molecular gene is a sequence of nucleotides in DNA that is transcribed to produce a functional RNA. There are two types of molecular genes: protei ...

or a

haplotype A haplotype (haploid genotype) is a group of alleles in an organism that are inherited together from a single parent. Many organisms contain genetic material (DNA) which is inherited from two parents. Normally these organisms have their DNA orga ...

containing multiple adjacent genes along a

chromosome A chromosome is a package of DNA containing part or all of the genetic material of an organism. In most chromosomes, the very long thin DNA fibers are coated with nucleosome-forming packaging proteins; in eukaryotic cells, the most import ...

. Given recombination, each gene can have a separate genetic lineages, even as the

population Population is a set of humans or other organisms in a given region or area. Governments conduct a census to quantify the resident population size within a given jurisdiction. The term is also applied to non-human animals, microorganisms, and pl ...

shares a single organismal lineage. In asexual

microbes A microorganism, or microbe, is an organism of microscopic size, which may exist in its single-celled form or as a colony of cells. The possible existence of unseen microbial life was suspected from antiquity, with an early attestation in ...

or somatic cells, cell lineages exactly match genetic lineages, and can be traced.

Incomplete lineage sorting

Incomplete lineage sorting describes when the

phylogenetic tree A phylogenetic tree or phylogeny is a graphical representation which shows the evolutionary history between a set of species or taxa during a specific time.Felsenstein J. (2004). ''Inferring Phylogenies'' Sinauer Associates: Sunderland, MA. In ...

for a gene does not match that of the

species A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...

. For example, while most human gene lineages coalesce first with chimpanzee lineages, and then with gorilla lineages, other configurations also occur.

Lineage selection

Lineage selection occurs when the frequency of members of one lineage changes relative to another lineage. It is useful for studying alleles with complex effects that play out over multiple generations, e.g. alleles that affect recombination, evolvability, or

altruism Altruism is the concern for the well-being of others, independently of personal benefit or reciprocity. The word ''altruism'' was popularised (and possibly coined) by the French philosopher Auguste Comte in French, as , for an antonym of egoi ...

. Lineage selection is also useful in determining the effects of mutations in highly structured environments such as tumors. Long-term

stochastic Stochastic (; ) is the property of being well-described by a random probability distribution. ''Stochasticity'' and ''randomness'' are technically distinct concepts: the former refers to a modeling approach, while the latter describes phenomena; i ...

outcomes of competition among lineages can be quantified within

mathematical model A mathematical model is an abstract and concrete, abstract description of a concrete system using mathematics, mathematical concepts and language of mathematics, language. The process of developing a mathematical model is termed ''mathematical m ...

s as the ratio of fixation probability : counterfixation probability. Inclusive fitness is equal to the average organismal fitness of individuals across the

probability distribution In probability theory and statistics, a probability distribution is a Function (mathematics), function that gives the probabilities of occurrence of possible events for an Experiment (probability theory), experiment. It is a mathematical descri ...

of possible lineages.

Tree sequence recording

Tree sequence recording describes efficient methods to record surviving lineages while conducting

computer simulation Computer simulation is the running of a mathematical model on a computer, the model being designed to represent the behaviour of, or the outcome of, a real-world or physical system. The reliability of some mathematical models can be determin ...

s of

population genetics Population genetics is a subfield of genetics that deals with genetic differences within and among populations, and is a part of evolutionary biology. Studies in this branch of biology examine such phenomena as Adaptation (biology), adaptation, s ...

. Resulting 'forward time'

s offer an alternative to 'backward time' coalescent theory. Tree sequence recording has been incorporated into the population simulation software SLiM.

Sexual lineages compared to asexual lineages

Sexual reproduction Sexual reproduction is a type of reproduction that involves a complex life cycle in which a gamete ( haploid reproductive cells, such as a sperm or egg cell) with a single set of chromosomes combines with another gamete to produce a zygote tha ...

is the most common form of reproduction in the genetic lineages of multicellular organisms, and a complete lack of sexual reproduction is relatively rare among such

organisms An organism is any living thing that functions as an individual. Such a definition raises more problems than it solves, not least because the concept of an individual is also difficult. Many criteria, few of them widely accepted, have been pr ...

, particularly

animals Animals are multicellular, eukaryotic organisms in the biological kingdom Animalia (). With few exceptions, animals consume organic material, breathe oxygen, have myocytes and are able to move, can reproduce sexually, and grow from a ...

. Sexual reproduction appears to have emerged very early in the evolution of

eukaryote The eukaryotes ( ) constitute the Domain (biology), domain of Eukaryota or Eukarya, organisms whose Cell (biology), cells have a membrane-bound cell nucleus, nucleus. All animals, plants, Fungus, fungi, seaweeds, and many unicellular organisms ...

s implying that the essential features of

meiosis Meiosis () is a special type of cell division of germ cells in sexually-reproducing organisms that produces the gametes, the sperm or egg cells. It involves two rounds of division that ultimately result in four cells, each with only one c ...

were already present in the earliest eukaryotic genetic lineage. Among eukaryotes, almost all lineages with asexual modes of reproduction maintain meiosis either in a modified form or as an alternative pathway. A constraint on a meiotic sexual lineage undergoing switching to an ameiotic, asexual form of reproduction appears to be the concomitant loss of the protective recombinational repair of DNA damage that is a key function of meiosis.Avise, J. (2008) Clonality: The Genetics, Ecology and Evolution of Sexual Abstinence in Vertebrate Animals. See pp. 22-25. Oxford University Press.

References

Mutation {{genetics-stub