if anyone can help, thank you! 10. \"Achondroplasia is an autosomal dominant dis
ID: 198372 • Letter: I
Question
if anyone can help, thank you!
10. "Achondroplasia is an autosomal dominant disorder. Guanine at position 1138 in the FGFR3 gene is one of the most mutable nucleotides identified in any human gene. Mutation of this nucleotide accounts for nearly 100% of achondroplasia; more than 80% of patients have a de novo mutation." A couple with normal height came to you with their daughter who is affected by achondroplasia. As a etic counselor, how would you explain the origin of the allele that caused Achondroplasia to this couple? Your answer has to be specific and incorporate information as provided. In order t credits, you have to show a clear understanding of how an inherited case differs from a sporadic case; or how mutation arises.Explanation / Answer
Achondroplasia is a form of short-limbed dwarfism. All people with achondroplasia have short stature. Characteristic features of achondroplasia include an average-size trunk, short arms and legs with particularly short upper arms and thighs, limited range of motion at the elbows, and an enlarged head. People with achondroplasia are generally of normal intelligence.The average height of an adult male with achondroplasia is 131 centimeters (4 feet, 4 inches), and the average height for adult females is 124 centimeters (4 feet, 1 inch).
Mutations in the FGFR3 gene cause achondroplasia. The FGFR3 gene provides instructions for making a protein that is involved in the development and maintenance of bone and brain tissue. Two specific mutations in the FGFR3 gene are responsible for almost all cases of achondroplasia. Researchers believe that these mutations cause the FGFR3 protein to be overly active, which interferes with skeletal development and leads to the disturbances in bone growth seen with this disorder. 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. In the remaining cases, people with achondroplasia have inherited an altered FGFR3 gene from one or two affected parents. Individuals who inherit two altered copies of this gene typically have a severe form of achondroplasia that causes extreme shortening of the bones and an underdeveloped rib cage. These individuals are usually stillborn or die shortly after birth from respiratory failure.
Genetic counseling is the process of providing individuals and families with information on the nature, inheritance, and implications of genetic disorders to help them make informed medical and personal decisions.
Mode of Inheritance
Achondroplasia is inherited in an autosomal dominant manner means the phenotype can be expressed in individuals who have one copy of a pathogenic variant at a particular locus (heterozygotes); specifically refers to a gene on one of the 22 pairs of autosomes (non-sex chromosomes).
How mutation occurs in achondroplasia:
Achondroplasia is caused by a gene alteration (mutation) in the FGFR3 gene. The FGFR3 gene makes a protein called fibroblast growth factor receptor 3 that is involved in converting cartilage to bone. FGFR3 is the only gene known to be associated with achondroplasia. It is a dominant genetic disease so only one copy of the FGFR3 gene needs to be mutated for symptoms to develop. Achondroplasia can be inherited from a parent with the disease. However, most cases of achondroplasia are the result of a new mutation in the FGFR3 gene, over 80 per cent of people with achondroplasia have parents who are unaffected.
Sporadic cases of achondroplasia have been associated with advanced paternal age, suggesting that these mutations occur preferentially during spermatogenesis.
Related Questions
Navigate
Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.