(Wikipedia.org 2013). However, these genes are usually
present in different individuals of a particular
species. Recently developed genomics techniques take
advantage of parallel genotyping of single feature
polymorphisms (SFPs) and other small differences
between two strain backgrounds (Deutschbauer and
Davis 2005). One of the tools used to identify
molecular markers associated with a trait in an
organism is bulked segregant analysis (BSA) which
measures the variation present in pools of segregants
that have been sorted according to phenotype and uses
the correlation between these measurements and the
pool phenotype to assign a likely map location (Brauer
et al. 2006). BSA relies on informative individuals
being grouped so that a particular genomic region is
studied against a randomized genetic background of
unlinked loci (Michelmore et al. 1991). This is an
improvement over methods that require individual
genotyping, as it simultaneously measures the average
genotype of progeny with a given phenotype (Brauer
et al. 2006). Also, the simplicity and low cost of BSA
have led to its use for complex traits including those
whose genetic control is unknown and is being used
increasingly to screen for quantitative trait loci (QTL)
(Mackay and Caligari 2000). Two contrasting bulks
for a trait in BSA will differ only at the locus harbouring
that trait and the minimum size of the samples
comprising the bulks is generally determined by the
frequency with which these unlinked loci might be
detected as polymorphic between the two bulks
(Mackay and Caligari 2000). While biotechnology