From Wikipedia, the free encyclopedia Interspersed repeat
Interspersed repeat
Interspersed repetitive DNA is found in all eukaryotic leads to the creation of new genes and new species dur-
genomes. Certain classes of these sequences propagate ing evolution[3]. By breaking the links that would oth-
themselves by RNA mediated transposition, and they erwise overwrite novel DNA sequence variations, inter-
have been called retrotransposons. Interspersed repeti- spersed repeats catalyse evolution, allowing the new
tive DNA elements allow new genes to evolve. They do genes and new species to develop.
this by uncoupling similar DNA sequences from gene
conversion during meiosis[1]. The recombinational
events of meiosis create heteroduplexes composed of
strands from each parental chromosome. These het-
eroduplexes lead to mismatch repair. The net result is
the homogenization and elimination of sequence differ-
ences during meiosis. Gene conversion can be viewed as
the force acting to create sequence identity within the Interspersed DNA elements
gene pool of a species. This is a cohesive force acting to
match up DNA sequences of individual organisms that catalyze the evolution of new
comprise a species. In effect the gene conversion causes
the DNA sequences to clump together within a species and
genes
by doing so creates the natural boundaries between DNA sequences are linked together in a gene pool by gene
species. The gene pool of a species consists of DNA se- conversion events. Insertion of an interspersed DNA el-
quences linked in a network by gene conversion events. ement breaks this linkage, allowing independent evolu-
tion of a new gene. The interspersed repeat is an isolat-
ing mechanism enabling new genes to evolve without in-
Intrachromosomal and inter- terference from the progenitor gene. Because insertion
chromosomal gene conversion of an interspersed repeat is a saltatory event the evo-
lution of the new gene will also be saltatory. Because
Gene conversion acts on DNA sequence homology as its speciation ultimately depends on the creation of new
substrate. There is no requirement that the sequence ho- genes, this naturally causes punctuated equilibria. Inter-
mologies lie at the allelic positions on their respective spersed repeats are thus responsible for punctuated evo-
chromosomes or even that the homologies lie on differ- lution and rapid modes of evolution.
ent chromosomes. Gene conversion events can occur be-
tween different members of a gene family situated on the
same chromosome[2]. When this happens, it is called in-
trachromosomal gene conversion as distinguished from
interchromosomal gene conversion. The effect of ho-
mogenizing DNA sequences is the same.
See also
Role of Interspersed Repetitive • Eukaryotic chromosome fine structure
DNA • Genomic organization
• L1Base
Repetitive sequences play the role of uncoupling the
gene conversion network, thereby allowing new genes
to evolve. The shorter Alu or SINE repetitive DNA are External links
specialized for uncoupling intrachromosomal gene con-
• http://www.repetitive-dna.org
version while the longer LINE repetitive DNA are spe-
cialized for uncoupling interchromosomal gene conver-
sion. In both cases, the interspersed repeats block gene References
conversion by inserting regions of non-homology within
[1] Schimenti JC, Duncan CH (February 1984).
otherwise similar DNA sequences. The homogenizing
"Ruminant globin gene structures suggest an
forces linking DNA sequences are thereby broken and the
evolutionary role for Alu-type repeats". Nucleic
DNA sequences are free to evolve independently. This
1
From Wikipedia, the free encyclopedia Interspersed repeat
Acids Res. 12 (3): 1641–55. doi:10.1093/nar/ doi:10.1073/pnas.80.19.5970. PMC 390199.
12.3.1641. PMC 318605. PMID 6322113. PMID 6310609. http://www.pnas.org/cgi/content/
http://nar.oxfordjournals.org/cgi/ abstract/80/19/5970.
pmidlookup?view=long&pmid=6322113. [3] Brunner AM, Schimenti JC, Duncan CH (September
[2] Hess JF, Fox M, Schmid C, Shen CK (October 1983). 1986). "Dual evolutionary modes in the bovine
"Molecular evolution of the human adult alpha- globin locus". Biochemistry 25 (18): 5028–35.
globin-like gene region: insertion and deletion of doi:10.1021/bi00366a009. PMID 3768329.
Alu family repeats and non-Alu DNA sequences". http://pubs.acs.org/doi/abs/10.1021/bi00366a009.
Proc. Natl. Acad. Sci. U.S.A. 80 (19): 5970–4. • MeSH Interspersed+Repetitive+Sequences
Retrieved from "http://en.wikipedia.org/w/index.php?title=Interspersed_repeat&oldid=461767251"
Categories:
• Mobile genetic elements
• Repetitive DNA sequences
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