Chapter 7, Problem 2NST

Campomelic dysplasia (CMD1) is a congenital human syndrome featuring malformation of bone and cartilage. It is caused by an autosomal dominant mutation of a gene located on chromosome 17. Consider the following observations in sequence, and in each case, draw whatever appropriate conclusions are warranted.

1. (a) Of those with the syndrome who are karyotypically 46, XY, approximately 75 percent are sex reversed, exhibiting a wide range of female characteristics.
2. (b) The nonmutant form of the gene, called SOX9, is expressed in the developing gonad of the XY male, but not the XX female.
3. (c) The SOX9 gene shares 71 percent amino acid coding sequence homology with the Y-linked SRY gene.
4. (d) CMD1 patients who exhibit a 46, XX karyotype develop as females, with no gonadal abnormalities.

HINT: This problem asks you to apply the information presented in this chapter to a real-life example. The key to its solution is knowing that some genes are activated and produce their normal product as a result of expression of products of other genes found on different chromosomes.