Biology concepts and applications

Biology

Dunne, Vanessa and Maselli, Ricardo a. (2004). Common founder effect of rapsyn N88K studied using intragenic markers. The Japan Society of Human Genetics and Springer-Verlag. 8 June 2004.

Many researchers believe that the rapsyn N88K gene, which has links to the preponderance of congenital myasthenic syndrome, is derived from a common founder effect, much as many other singularly associated genetic mutations. To date no definitive answer has been found in other research in regard to this hypothesis, but the authors of this article believe that by the use and observation of intragenic markers they may prove this to be the case.

Common founder effect is the minimization of a particular gene pool that creates a particular type of genetic drifting. This drifting in founder effect is caused by a limited number of original organisms in a startup population creating a restricted gene pool for its future descendants to draws from. This smaller population has the effect upon the descendants of a reduced genetic variation from the larger original gene pool. This also has the effect of creating a non-random sample of the genes, as opposed ot the wide variety of effect in the larger population. Founder effect creates a situation closer to hardy-Weinberg equilibrium than would otherwise be found.

The authors study was comprised of "…six patients with symptoms of CMS since birth from six independent families who carried the N88K mutation. Three patients were homozygous for the mutation, and three were heterozygous and carried a second mutation (L14P, 46 insC, orY269X)" (Dunne, & Maselli, 2005, p.367). Although this was certainly a rather small sample the group consisted of member from various genetic backgrounds. Two of the families were from Spain, one family was from India and Hindu and the other three families were of northern European descent. For intragenic markers they chose used seven intragenic single nucleotide polymorphisms (SNPs) spanning 8 kb to characterize the haplotype that is associated with N88K. They were searching to discover if there was a common haplotype associated with the N88K mutation, which would support the hypothesis that the creation of the genetic stream was assisted by the founder effect. The Congenital myasthenic syndromes are specific to certain hereditary traits:

Congenital myasthenic syndromes (CMS) constitute a group of rare diseases heterogeneous both in terms of their mode of hereditary transmission (recessive and dominant forms) and their pathophysiology (with presynaptic, synaptic, and postsynaptic defects). They are responsible for dysfunction of neuromuscular transmission giving rise to a condition of muscle weakness which is accentuated by exertion. In most cases, CMS begin in early childhood but later onset in adulthood is possible. Severity also varies from severe with respiratory failure to mild expression. (Richard, P, et. Al., 2004, p. 81)