How does the homozygous condition of achondroplasia affect survival?

The homozygous condition of achondroplasia is indeed lethal, primarily due to the severe complications that arise in the development of the fetus. Achondroplasia is typically caused by a mutation in the FGFR3 gene, and it is usually inherited in an autosomal dominant manner. Individuals who inherit two copies of this mutated gene (homozygous) do not usually survive to birth or infancy due to the resulting skeletal abnormalities that severely impact critical bodily functions such as respiration.

In contrast, individuals who are heterozygous for achondroplasia (having one copy of the mutated gene) can lead a normal life and have a typical lifespan. Therefore, the homozygous condition represents a significant deviation from the typical presentation of the disorder, which is why it is recognized as lethal. This understanding is crucial for professionals in genetics and healthcare, as well as for midwives who may encounter such cases during prenatal care.