Genetic map of MTP mutations in patients with abetalipoproteinemia. The map shows the genomic structure of MTP gene. Black boxes represent exons; dotted lines point to mutation positions. Above the map are single-nucleotide and small insertion-deletion mutations. Nucleotide position in reference to the first ATG of MTP cDNA (GenBank Accession No. NM_000253) are shown. Directly under the linear map are splicing mutations. The position relative to the intron-exon boundary is shown numerically. Larger deletions are shown as horizontal lines below the linear map, with the span of the deleted region indicated by text label.