You are a geneticist specialising in paediatric diseases and disorders. One day Martin and Lorna bring their daughter Ruby to see you. Ruby is 4 years old and her parents are concerned that she appears to have teeth malformation, sparse hair and only appears to sweat in certain patches on her skin. In fact, Ruby’s symptoms appear to be mosaic in nature. You suspect that Ruby has mosaic X-linked hypohidrotic ectoplasmic dysplasia. You take blood from Ruby for DNA testing and send it to the lab. When the results are returned to you, your suspicions are confirmed. Ruby has a mutation in the gene EDA. You call Martin and Lorna and ask them to come to see you. When they arrive, you take out of your drawer a series of photos and diagrams to explain Ruby’s condition. Provide a detailed explanation of the genetic aspect of this disorder to Martin and Lorna. Assume that Ruby’s parents have a basic knowledge of gene expression and inheritance. In your answer, include all of the diagrams/images below.

Your explanation should include (but not be limited to):

a. Location of EDA gene and normal role of EDA protein product.

b. The effect of mutation in this gene in the body, and how this leads to the symptoms of X-linked hypohidrotic ectoplasmic dysplasia.

c. Mosaicism, and its potential relevance to this disorder, as one of the hypotheses surrounding the mosaic nature of Ruby’s condition.