At various times, proposals have also been put forth to implement multiple user-defined Null markers in SQL.
Because SQL 2003 defines all Null markers as being unequal to one another, a special definition was required in order to group Nulls together when performing certain operations.
Because of the complexity of the Null-handling and logic systems required to support multiple Null markers, none of these proposals have gained widespread acceptance.
Any associations found between these null markers and phenotypes are attributed to the population stratification.
Both methods attained similar results with an estimate of π (the proportion of null markers) ranging from 59%to67%7% in the Bayes Cπ analysis in line with the reshuffling approach (data not shown).
Genomic Control (GC) (Devlin and Roeder, 1999; Devlin et al., 2004) uses supplementary loci (called null markers) to correct for the population effect, which is assumed to be uniform across the genome.
Prior to selecting this ramet, six short simple repeat (SSR) marker loci – specifically PtTX2123, PtTX4058, PtTX4093, PtTX4181, PtTX3013 and PtTX3052 [53] – and the CAD-null marker [54] were used to genotype ten 7-56 and two non-7-56 ramets in a double blind experiment.
To investigate if tetrasomic recombination was influenced by genetic factors, we carried out quantitative trait loci analyses using, as a phenotype, the number of null PCR marker data points for each RIL from the PCR marker linkage map of Shirasawa et al. (2013) with only codominant markers (supporting information, File S1, worksheet "PCR and SMA," line 1205).
Single-marker analysis for tendency to undergo tetrasomic recombination (number of null PCR markers per genotype) indicated significant marker associations on LGA02 and LGA07.
In Codd's book, these two Null-type markers are referred to as 'A-Values' and 'I-Values', representing 'Missing But Applicable' and 'Missing But Inapplicable', respectively.
