Acho ndroplasia is a common cause of dwarfism in humans. All individuals with acho ndroplasia are thought to be heterozygous at the locus that controls this trait. When two individuals with acho ndroplasia have children, the offspring occur in a ratio of 2 acho ndroplasia:1 wild type. What is the most likely explanation for these observations

The question is incomplete. The complete question is:

Acho ndroplasia is a common cause of dwarfism in humans. All individuals with acho ndroplasia are thought to be heterozygous at the locus that controls this trait. When two individuals with acho ndroplasia have children, the offspring occur in a ratio of 2 acho ndroplasia:1 wild type. What is the most likely explanation for these observations

A. The allele that causes acho ndroplasia is a late-onset lethal allele.

B. The allele that causes acho ndroplasia is a recessive lethal allele.

C. The allele that causes acho ndroplasia is a dominant lethal allele.

D. Acho ndroplasia is incompletely dominant to the normal condition.

E. Acho ndroplasia is codominant to the normal condition.

Answer:

B. The allele that causes acho ndroplasia is a recessive lethal allele.

Explanation:

According to the given information, acho ndroplasia is a genetic disorder and the individuals with the disorder are heterozygous. The individuals with homozygous recessive genotype do not survive as the allele for the disorder is lethal in the homozygous condition. Let's assume that the allele "a" causes acho ndroplasia while the allele "A" imparts normal height to the individuals. Two heterozygous parents each with genotype "Aa" would produce a progeny in the following ratio=

Aa x Aa = 1 AA (normal height) : 2 Aa (acho ndroplasia) : 1 aa (do not survive).