Molecular analysis of the SMN and NAIP genes in Saudi spinal muscular atrophy patients.

In this study we examined the deletion of the SMN and NAIP genes in 14 Saudi families (16 patients and 38 relatives of the patients, including parents and siblings) and six healthy Saudi volunteers. The homozygous deletions of exons 7 and 8 of the telomeric SMN gene and exon 5 of the NAIP gene were found in seven out of eight spinal muscular atrophy (SMA) type-I patients. In seven SMA type-II patients, exons 7 and 8 of telomeric SMN were deleted in six cases and exon 5 of NAIP was deleted in three cases. Three patients with SMA diagnosis did not show either of the above deletions. All control Saudi volunteers and all but two family members of the patients had both normal SMN and NAIP genes. Our results show that the incidence of NAIP deletion is higher in the more severe SMA cases and the dual deletions of the SMN and NAIP genes are more common in Saudi SMA type-I patients compared to patients of other ethnic groups.

Mitochondrial DNA sequence variation and genetic stock structure of Atlantic cod (Gadus morhua) from bay and offshore locations on the Newfoundland continental shelf.

Bay cod, Atlantic cod (Gadus morhua) that over-winter in the deep-water bays of north-eastern Newfoundland, have historically been regarded as distinct in migration and spawning behaviour from offshore (Grand Bank) cod stocks. To investigate their genetic relationships, we determined the DNA sequence of a 307-base-pair portion of the mitochondrial cytochrome b gene for 236 adult cod taken from the waters off north-eastern Newfoundland, including fish found over-wintering and spawning in Trinity Bay. Although 17 genotypes were found, a single common genotype occurs at a frequency of greater than 80% in all samples, and no alternative genotype occurs at a frequency of greater than 3%. Genotype proportions did not differ significantly among samples. Measures of genetic subdivision among sampling locations are nil. Cod over-wintering in Trinity Bay are not genetically distinct from offshore cod. In combination with tagging and physiological studies, these data suggest that there is sufficient movement of cod between bay and offshore locations to prevent the development or maintenance of independent inshore stocks. Adult cod that over-winter in Trinity Bay appear to represent an assemblage of temporarily nonmigratory fish that have become physiologically acclimated to cold-water inshore environments. The pattern of genetic variation in northern cod suggests a recent population structure characterized by extensive movement of contemporary individuals superimposed on an older structure characterized by a bottleneck in the population size of cod in the north-western Atlantic.