Biomedical Engineering Reference
In-Depth Information
However,. note. that. the. performance. of. transposition. will. be. affected.
by. the. size. of. the. lanking. sequence,. especially. when. a. small. population.
size. is. encountered.. If. a. long. sequence. is. defined,. the. average. length. of.
the.transposon.increases..The.occurrence.probability.of.transposition.will.
then. be. reduced. since. the. next. same. lanking. sequence. (or. reverse. lank-
ing.sequence).is.less.likely.to.be.found..As.a.consequence.of.having.fewer.
transpositions. of. genes,. minimal. effect. is. expected.. Moreover,. extra. com-
putational.effort.is.required.because.the.sequence.searching.is.tedious.on.a.
bit-by-bit.basis.
3.2.2 bacterial Operations
Horizontal.transmission.is.not.the.only.cause.of.genetic.transfer.in.chromo-
somes.. Similar. effects. are. also. observed. when. bacteria. attack. a. cell.. In. the.
past.few.years,.a.series.of.computational.bacterial.operations.has.been.pro-
posed..These.operations,.though.inspired.by.another.source,.have.somehow.
similar.effects.in.altering.a.chromosome.
3.2.2.1 Transduction
Transduction. [18,41-43,64]. is. a. process. involving. a. virus. that. accidentally.
picks.up.a.copy.of.genes.from.a.host.cell.and.inserts.it.in.the.chromosome.
of.an.infected.cell..With.such.a.process,.features.of.a.single.bacterium.can.be.
passed.to.the.entire.population.
The.computational.transduction.mechanism.is.depicted.in
.
Figure 3.5.
.
A.
chromosome.is.divided.into.
p
parts,.each.of.which.may.represent.a.system.
parameter..The.chromosome.is.then.reproduced.into.
m
clones..A.randomly.
chosen.gene.portion,.say.the.
i
th.part.of.(
m
−.1).clones,.is.mutated..The.elite.
among. the
m
clones. is. then. selected,. and. its.
i
th. part. is. transferred. to. the.
other.(
m
.−.1).clones,.replacing.the
i
th.part.of.all.the.other.clones..The.process.
of.mutation-evaluation-selection-replacement.is.repeated,.and.each.time.a.
new.part.(i.e.,.not.selected.before).is.randomly.chosen..When.all.the
p
parts.
have. been. processed,. only. one. clone. is. kept. in. the. population;. the. others.
are.discarded.
In. References. 18,. 41-43,. and. 64,. transduction. is. embedded. into. a. GA. to.
form.a.new.algorithm,.named.the.pseudobacterial.genetic.algorithm.(PBGA)..
In.a.PBGA,.transduction.is.performed.prior.to.crossover,.while.mutation.is.
abandoned..It.has.been.used.to.solve.several.fuzzy.system.design.problems,.
and.it.outperforms.conventional.GA.by.locating.the.optimal.solutions.more.
efficiently.
Transduction.realizes.a.local.improvement.mechanism.in.parts.in.a.chro-
mosome.while.interactions.among.chromosomes.are.performed.through.the.
crossover. operation.. The. performance. of. transduction. highly. depends. on.
the. choice. of. parts. in. the. chromosomes,. implying. that. the. coding. scheme.
is.important..For.example,.each.part.of.the.chromosome.represents.a.fuzzy.
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