BACKGROUND Numerous epidemiological factors affect the probability of developing breast or ovarian cancer, but no predictor is as determinant as inheriting a mutation in BRCA1 or BRCA2. The concept of the founder effect explains the reduced genetic variability in some populations, according to the theory that new populations can be formed from a reduced number of individuals, so the new populat...

The theory of founder-effect speciation proposes that colonization by very few individuals of an empty habitat favors rapid genetic changes and the evolution of a new species. We report here the results obtained in a 10-year-long and large-scale experiment with Drosophila pseudoobscura designed to test the theory. In our experimental protocol, populations are established with variable numbers o...

We analyzed the polymorphic (CAG)n and (GGC)n repeats of the androgen receptor gene in 113 unrelated X-linked spinal and bulbar muscular atrophy (SBMA) X chromosomes and 173 control X chromosomes in Japanese males. The control chromosomes had an average CAG repeat number of 21 +/- 3 with a range from 14-32 repeat units, and SBMA chromosomes had a range from 40-55 with a median of 47 +/- 3 copie...

We describe a mutation and haplotype analysis of Papillon-Lefèvre syndrome probands that provides evidence of a founder effect for four separate cathepsin C mutations. A total of 25 different cathepsin C mutations have been reported in 32 families with Papillon-Lefèvre syndrome (PLS) and associated conditions. A characteristic of these findings is the diversity of different cathepsin C mutation...

Homozygous STAT5B mutations causing growth hormone insensitivity with immune dysfunction were described in 10 patients since 2003, including two Brazilian brothers from the south of Brazil. Our objectives were to evaluate the prevalence of their STAT5B mutation in this region and to analyze the presence of a founder effect. We obtained DNA samples from 1,205 local inhabitants, 48 relatives of t...

Genetic and paleoanthropological evidence is in accord that today's human population is the result of a great demic (demographic and geographic) expansion that began approximately 45,000 to 60,000 y ago in Africa and rapidly resulted in human occupation of almost all of the Earth's habitable regions. Genomic data from contemporary humans suggest that this expansion was accompanied by a continuo...

BACKGROUND All honey bee species (Apis spp) share the same sex determination mechanism using the complementary sex determination (csd) gene. Only individuals heterogeneous at the csd allele develop into females, and the homozygous develop into diploid males, which do not survive. The honeybees are therefore under selection pressure to generate new csd alleles. Previous studies have shown that t...

Hemophilia A is a heterogeneous hemorrhagic disorder caused by a large number of mutations. Recurrent mutations are rare, except intron 22 and intron 1 inversions. The substitution of a cytosine to a thymine at nucleotide 6046 in F8 gene was identified in a group of Italian patients affected by hemophilia A from a specific region of Northern Italy with a prevalence of 7.6%. This F8 variant was ...