A mutation in gene in a case of fertilization.

Congenital adrenal hyperplasia, one of the most frequent autosome recessive disorders, is caused by defects in steroidogenic enzymes involved in the cortisol biosynthesis. Approximately 95% of the cases are caused by abnormal function of the 21-hydroxylase enzyme. This deficiency leads to androgen excess, consequently, to virilization and rapid somatic growth with accelerated skeletal maturation.

Screening for the GJB2 c.-3170 G>A (IVS 1+1 G>A) mutation in Brazilian deaf individuals using multiplex ligation-dependent probe amplification.

Mutations in GJB2 gene are the most common cause of nonsyndromic sensorineural recessive hearing loss. One specific mutation, c.35delG, is the most frequent in the majority of Caucasian populations and may account for up to 70% of all GJB2 mutations.