Biomedical Engineering Reference
In-Depth Information
Homothallic
. switching. (
HO
). endonuclease-induced. double-strand.
breaks,.which.are.lethal.
.
3.. The.
gag
.region.of.the.retrovirus.of.the.human.endogenous.retrovirus-
like.(
HERV-L
).family.derived.the.
Friendvirussusceptibility1
(
Fv1
).gene.
of.mice.[1]..It.protected.the.host.by.conferring.retroviral.resistance.
.
4.. Viviparous. organisms. with. active. immune. systems. face. a. problem.
that.the.maternal.immune.system.treats.the.developing.embryo.as.a.
“foreign”.organism..The.embryo.would.be.attacked.by.the.immune.
system. if. unprotected.. However,. endogenous. retroelements. in. all.
mammals. (e.g.,.
endogenous retrovirus-3
. [
ERV3
]. in. humans). were.
expressed.at.high.levels.in.specific.tissues..The.purpose.of.these.tis-
sue.expressions.(e.g.,.in.the.placenta).was.to.protect.the.embryo.from.
being.attacked.by.the.maternal.immune.system.[27,60].
3.2 OverviewofComputationalGeneTransposition
Inspired.by.the.mechanisms.of.gene.transposition,.several.related.computa-
tional.algorithms.have.been.proposed,.and.they.are.briefly.summarized.next.
3.2.1 Sexual or asexual Transposition
In. References. 47-51,. gene. transposition. operations. were. suggested.. The.
genes.to.be.transposed.are.determined.by.referring.to.a.flanking.sequence.
that. is. randomly. selected.. An. example. is. given. in.
Figure 3.3..
A. flanking.
sequence. consisting. of. two. genes. bc. is. randomly. selected. and. indicated.
by. the. pointer p.. It. is. then. to. search. the. next. identical. or. inverse. lanking.
sequence.in.the.chromosome..If.successfully.found,.a.transposon.is.specified.
by.including.the.genes.starting.at.the.end.of.the.first.flanking.sequence.to.
the.end.of.the.second.lanking.sequence..In.the.example.given.in
.
Figure 3.3
,.
dbc.is.the.transposon.
The. transposon. can. undergo. sexual. or. asexual. transposition.. In. sexual.
transposition,. two. chromosomes. are. involved,. while. only. one. chromo-
some.is.involved.in.asexual.transposition..For.sexual.transposition,.two.dif-
ferent. ways. are. possible. to. generate. the. resultant. chromosomes,. as. given.
in.
Figure 3.3
..
The. first. method. is. called. tournament-based. transposition,.
for. which. the. transposon. is. pasted. at. the. position. right. after. the. lanking.
sequence.found.in.another.chromosome,.but.the.original.chromosome.is.kept.
unchanged..Another.way.is.simple.transposition..The.two.gene.segments.in.
the.corresponding.chromosomes.are.swapped,.as.shown.in.
Figure 3.3.
For. asexual. transposition,. after. identifying. the. transposon. by. finding.
the. first. and. the. second. flanking. sequences,. a. third. flanking. sequence. in.
the. same. chromosome. is. searched.. An. insertion. point. is. then. defined,. as.
Search WWH ::
Custom Search