First cousin marriages showed high b-thalassemia affliction than in unrelated couples and total consanguinity rate among parents of b-thalassemic children was 77.39% while the

coefficient of inbreeding calculated was 0.0455.

The

coefficient of inbreeding ([F.sub.IS]) was calculated using the FSTAT software (Goudet, 2002).

On the whole, the results support the theoretical expectation that inbreeding depression should be directly proportional to the coefficient of inbreeding, F, if all loci combine additively (Falconer 1989).

The simplest way commonly used to express the magnitude of inbreeding depression is to give the average reduction in mean value per 10% increase in F (the coefficient of inbreeding), or the slope of the regression of the measured character on F.

The level of inbreeding in a population can be measured by the

coefficient of inbreeding (F), which is the probability that the two alleles at a locus in an individual are identical by descent (IBD).

To investigate fitness differences between selfed and outcrossed progeny, the coefficient of inbreeding depression 6) was calculated according to Lande and Schemske (1985),

appendiculatum and the magnitude of the coefficient of inbreeding depression [delta] increased significantly through time (Kendall's correlation coefficient (tau) = 0.648, P < 0.003; Fig.

64), [f.sub.t] being the coefficient of inbreeding in generation t.

That is the value of the inbreeding effective size in the first generation in this case because, if there are equal number of sexes, a proportion 2/N of matings are expected to be between full-sibs and thus the expected coefficient of inbreeding is 1/2N (Ugarte et al., 1990).