Gene flow: Difference between revisions

From Citizendium
Jump to navigation Jump to search
imported>David Tribe
imported>David Tribe
Line 16: Line 16:
:''See also [[Horizontal gene transfer]]''
:''See also [[Horizontal gene transfer]]''


Genes can flow between species by a variety of mechanisms, including cross-hybridization (as in many land plants <ref>Rieseberg, L.H., Kim, M. J., and Seiler, G. J. (1999). Introgression between cultivated sunflowers and a sympatric wild relative, ''Helianthus petiolaris'' (Asteraceae). Int. J. Plant Sci 160, p102-108.</ref>, during phagocytosis of food in unicellular protists <ref>Loftus B, Anderson I, Davies R, Alsmark UCM, Samuelson J, Amedeo P, Roncaglia P, Berriman M, Hirt RP, Mann BJ, Nozaki T, Suh B, Pop M, Duchene M, Ackers J, Tannich E, Leippe M, Hofer M, Bruchhaus I, Willhoeft U, Bhattacharya A, Chillingworth T, Churcher C, Hance Z, Harris B, Harris D, Jagels K, Moule S, Mungall K, Ormond D, Squares R, Whitehead S, Quail MA, Rabbinowitsch E, Norbertczak H, Price C, Wang Z, Guillen N, Gilchrist C, Stroup SE, Bhattacharya S, Lohia A, Foster PG, Sicheritz-Ponten T, Weber C, Singh U, Mukherjee C, El- Sayed NM, Petri WAJ, Clark CG, Embley TM, Barrell B, Fraser CM, Hall N: The genome of the protist parasite  ''Entamoeba histolytica''. Nature 2005, 433(7028):865-868.</ref> <ref>Huang J, Mullapudi N, Lancto CA, Scott M, Abrahamsen MS, Kissinger JC: Phylogenomic evidence supports past [[endosymbiosis]], intracellular and horizontal gene transfer in Cryptosporidium parvum. Genome Biol 2004, 5(11):R88.</ref>, which often take up new genes from bacteria they engulf, or direct DNA uptake (as in bacterial DNA [[transformation]] and promiscuous [[conjugation]]al mating by bacteria <ref>[http://www2.nau.edu/~bah/BIO471/Reader/Pennisi_2003.pdf]</ref>.  Viruses can transfer genes between species <ref>[http://66.102.7.104/search?q=cache:tpICVNWaTbgJ:non.fiction.org/lj/community/ref_courses/3484/enmicro.pdf+sex+evolution+%22Horizontal+gene+transfer%22+-human+Conjugation+RNA+DNA&hl=en]</ref>.  
Genes can flow between species by a variety of mechanisms, including cross-hybridization (as in many land plants <ref>Rieseberg, L.H., Kim, M. J., and Seiler, G. J. (1999). Introgression between cultivated sunflowers and a sympatric wild relative, ''Helianthus petiolaris'' (Asteraceae). Int. J. Plant Sci 160, p102-108.</ref>, during phagocytosis of food in unicellular protists <ref>Loftus B, Anderson I, Davies R, Alsmark UCM, Samuelson J, Amedeo P, Roncaglia P, Berriman M, Hirt RP, Mann BJ, Nozaki T, Suh B, Pop M, Duchene M, Ackers J, Tannich E, Leippe M, Hofer M, Bruchhaus I, Willhoeft U, Bhattacharya A, Chillingworth T, Churcher C, Hance Z, Harris B, Harris D, Jagels K, Moule S, Mungall K, Ormond D, Squares R, Whitehead S, Quail MA, Rabbinowitsch E, Norbertczak H, Price C, Wang Z, Guillen N, Gilchrist C, Stroup SE, Bhattacharya S, Lohia A, Foster PG, Sicheritz-Ponten T, Weber C, Singh U, Mukherjee C, El- Sayed NM, Petri WAJ, Clark CG, Embley TM, Barrell B, Fraser CM, Hall N: The genome of the protist parasite  ''Entamoeba histolytica''. Nature 2005, 433(7028):865-868.</ref> <ref>Huang J, Mullapudi N, Lancto CA, Scott M, Abrahamsen MS, Kissinger JC: Phylogenomic evidence supports past [[endosymbiosis]], intracellular and horizontal gene transfer in Cryptosporidium parvum. Genome Biol 2004, 5(11):R88.</ref>, which often take up new genes from bacteria they engulf, or direct DNA uptake (as in bacterial DNA [[transformation]] and promiscuous [[conjugation]]al mating by bacteria <ref>[http://www2.nau.edu/~bah/BIO471/Reader/Pennisi_2003.pdf Pennisi, E. (2004) Researchers Trade Insights About Gene Swapping:Genes that move between species play by rules that microbial experts are just beginning to discern SCIENCE VOL 305 16 JULY 2004 p334-335]</ref>.  Viruses can transfer genes between species <ref>[http://66.102.7.104/search?q=cache:tpICVNWaTbgJ:non.fiction.org/lj/community/ref_courses/3484/enmicro.pdf+sex+evolution+%22Horizontal+gene+transfer%22+-human+Conjugation+RNA+DNA&hl=en]</ref>.  


"Sequence comparisons suggest recent horizontal transfer of many [[gene]]s among diverse [[species]] including across the boundaries of [[phylogenetic]] "domains". Thus determining the phylogenetic history of a species can not be done conclusively by determining evolutionary trees for single genes." <ref>[http://opbs.okstate.edu/~melcher/MG/MGW3/MG334.html]</ref>
"Sequence comparisons suggest recent horizontal transfer of many [[gene]]s among diverse [[species]] including across the boundaries of [[phylogenetic]] "domains". Thus determining the phylogenetic history of a species can not be done conclusively by determining evolutionary trees for single genes." <ref>[http://opbs.okstate.edu/~melcher/MG/MGW3/MG334.html]</ref>

Revision as of 15:38, 3 December 2006

Gene flow (also known as gene migration) is the transfer of alleles of genes from one population to another.

Migration into or out of a population may be responsible for a marked change in allele frequencies (the number of individual members carrying a particular variant of a gene). Immigration may result in the addition of new genetic material to the established gene pool of a particular species or population, and conversely emigration may result in the removal of genetic material.

There are a number of factors that affect the rate of gene flow between different populations. One of the most significant factors is mobility, and animals tend to be more mobile than plants. Greater mobility of an individual tends to give it greater migratory potential.

Barriers to gene flow

Physical barriers to gene flow are usually, but not always, natural. They may include impassable mountain ranges or vast deserts, or something so simple as the Great Wall of China, which has hindered the natural flow of plant genes [1]. Examples of the same species which grow on either side have been shown to be genetically different.

Gene flow in humans

Gene flow has been observed in humans, for example in the United States, where a white European population and a black West African population were recently brought together. The Duffy blood group gives carriers some resistance to malaria, and as a result in West Africa, where malaria is prevalent, the Fyo allele is essentially one hundred percent. In Europe, which has much lower levels of malaria, have either allele Fya or Fyb. By measuring the frequencies, the rate of gene flow between the two populations can be measured, showing that gene flow is greater in the Northern U.S. than in the South.

Gene flow between species

See also Horizontal gene transfer

Genes can flow between species by a variety of mechanisms, including cross-hybridization (as in many land plants [2], during phagocytosis of food in unicellular protists [3] [4], which often take up new genes from bacteria they engulf, or direct DNA uptake (as in bacterial DNA transformation and promiscuous conjugational mating by bacteria [5]. Viruses can transfer genes between species [6].

"Sequence comparisons suggest recent horizontal transfer of many genes among diverse species including across the boundaries of phylogenetic "domains". Thus determining the phylogenetic history of a species can not be done conclusively by determining evolutionary trees for single genes." [7]

Biologist Gogarten suggests "the original metaphor of a tree no longer fits the data from recent genome research" therefore "biologists [should] use the metaphor of a mosaic to describe the different histories combined in individual genomes and use [the] metaphor of a net to visualize the rich exchange and cooperative effects of HGT among microbes." [8]

"Using single genes as phylogenetic markers, it is difficult to trace organismal phylogeny in the presence of HGT [horizontal gene transfer]. Combining the simple coalescence model of cladogenesis with rare HGT [horizontal gene transfer] events suggest there was no single last common ancestor that contained all of the genes ancestral to those shared among the three domains of life. Each contemporary molecule has its own history and traces back to an individual molecule cenancestor. However, these molecular ancestors were likely to be present in different organisms at different times." [9]

In pathogenic microorganisms, particularly when rates of horizontal gene transfer are high due to processes such as DNA transformation that occurs with some organisms inhabiting the upper respiratory tract of humans, evolutionary lineages can still be analysed by considering DNA sequence change that occurs in several genes. This techniques is called multi-locus sequence typing[10] [11] [12] [13].

Models of gene flow

Models of gene flow can be derived from population genetics, e.g. Sewall Wright's neighborhood model, Wright's island model and the stepping stone model.

Template:Sect-stub

References

  1. ↑ [1]
  2. ↑ Rieseberg, L.H., Kim, M. J., and Seiler, G. J. (1999). Introgression between cultivated sunflowers and a sympatric wild relative, Helianthus petiolaris (Asteraceae). Int. J. Plant Sci 160, p102-108.
  3. ↑ Loftus B, Anderson I, Davies R, Alsmark UCM, Samuelson J, Amedeo P, Roncaglia P, Berriman M, Hirt RP, Mann BJ, Nozaki T, Suh B, Pop M, Duchene M, Ackers J, Tannich E, Leippe M, Hofer M, Bruchhaus I, Willhoeft U, Bhattacharya A, Chillingworth T, Churcher C, Hance Z, Harris B, Harris D, Jagels K, Moule S, Mungall K, Ormond D, Squares R, Whitehead S, Quail MA, Rabbinowitsch E, Norbertczak H, Price C, Wang Z, Guillen N, Gilchrist C, Stroup SE, Bhattacharya S, Lohia A, Foster PG, Sicheritz-Ponten T, Weber C, Singh U, Mukherjee C, El- Sayed NM, Petri WAJ, Clark CG, Embley TM, Barrell B, Fraser CM, Hall N: The genome of the protist parasite Entamoeba histolytica. Nature 2005, 433(7028):865-868.
  4. ↑ Huang J, Mullapudi N, Lancto CA, Scott M, Abrahamsen MS, Kissinger JC: Phylogenomic evidence supports past endosymbiosis, intracellular and horizontal gene transfer in Cryptosporidium parvum. Genome Biol 2004, 5(11):R88.
  5. ↑ Pennisi, E. (2004) Researchers Trade Insights About Gene Swapping:Genes that move between species play by rules that microbial experts are just beginning to discern SCIENCE VOL 305 16 JULY 2004 p334-335
  6. ↑ [2]
  7. ↑ [3]
  8. ↑ [4]
  9. ↑ [5]
  10. ↑ Urwin R, Maiden MC. (2006) Multi-locus sequence typing: a tool for global epidemiology.Trends Microbiol. 2003 Oct;11(10):479-87. Review.
  11. ↑ Delorme C, Poyart C, Ehrlich SD, Renault P., (2006) Extent of Horizontal Gene Transfer in Evolution of Streptococci of the Salivarius Group. J Bacteriol. 2006 Nov 3; [Epub ahead of print] PMID: 17085557
  12. ↑ Johnson JR, Owens KL, Clabots CR, Weissman SJ, Cannon SB. (2006) Phylogenetic relationships among clonal groups of extraintestinal pathogenic Escherichia coli as assessed by multi-locus sequence analysis. Microbes Infect. 2006 Jun;8(7):1702-13. Epub 2006 Apr 21.
  13. ↑ Jolley KA, Chan MS, Maiden MC.(2004) mlstdbNet - distributed multi-locus sequence typing (MLST) databases.BMC Bioinformatics. 2004 Jul 1;5:86.
  • Su, H et al. (2003) "The Great Wall of China: a physical barrier to gene flow?." Heredity, Volume 9 Pages 212-219

Template:Evolution

pdc:Gene Flow de:Genfluss es:Flujo genético he:זרימת גנים pt:Fluxo gênico sv:Genflöde

Retrieved from "https://citizendium.org/wiki/index.php?title=Gene_flow&oldid=81430"