PATHOLOGY

Detailed explanation-1: -Achondroplasia is an autosomal dominant bone disorder that causes dwarfism. While the inheritance of one achondroplasia allele can cause the disease, the inheritance of two recessive lethal alleles is fatal.

Detailed explanation-2: -Achondroplasia is inherited in an autosomal dominant pattern, which means one copy of the altered gene in each cell is sufficient to cause the disorder. About 80 percent of people with achondroplasia have average-size parents; these cases result from new mutations in the FGFR3 gene.

Detailed explanation-3: -In the case of achondroplasia, the homozygous dominant genotype results in a lethal phenotype. These fetuses are stillborn or die shortly after birth. The phenotype is determined by a dominant allele that interferes with bone growth during development.

Detailed explanation-4: -Achondroplasia is an autosomal dominant condition and has three main forms. The lethal homozygous form, the non-lethal heterozygous form and the third in which the achondroplasia is severe and is associated with developmental delay and acanthosis nigricans (SADDAN).

Detailed explanation-5: -Some alleles associated with human genetic disorders are recessive lethal. For example, this is true of the allele that causes achondroplasia, a form of dwarfism. A person heterozygous for this allele will have shortened limbs and short stature (achondroplasia), a condition that is not lethal.