Putative null mutations

The yeast ACCl 3 -tail was used to complement ACCl null mutation. These genes encode a full-length plastid enzyme, with or without the putative chloro-plast transit peptide, as well as five chimeric cytosolic/plastid proteins (Fig. 9.3). 

In general, null alleles are associated with the classic early-onset phenotype, whereas missense mutations which lead to defective proteins that exhibit residual enzyme activity lead to attenuated phenotypes (Froissart et al., 2002). However, studies of genotype-phenotype correlation have revealed a lack of perfect concordance, which suggests other factors may be involved that influence disease outcome (Froissart et al., 2002). At present, the putative factors that modify LSD-phenotypes among patients with identical genotypes remain obscure. 

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