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Chapter 16. Of Fruit Flies, Mice, and Patients: Tying It All Together

You see a patient with Wolf-Hirschhorn syndrome (deletion 4p). The parents have spent a lot of time on the internet. They have read that the gene for achondroplasia is in this region. They understand that this means that their child is missing one copy of the achondroplasia gene. Thus they ask you if they should implement the surveillance recommendations for achondroplasia in their child. You would be correct in telling them that:

A. Achondroplasia surveillance should be started immediately.

B. The first step to answer their question would be to sequence the achondroplasia gene.

C. It is probably time to start growth hormone therapy to avoid the extreme short stature seen in achondroplasia.

D. Forget looking on the internet for answers, this will only confuse them.

E. The pathogenesis of achondroplasia is not haplo-insufficiency, so they do not need to worry about achondroplasia related issues in their child.

E is the correct answer.

  • A. Achondroplasia is not caused by a missing copy of the gene.

  • B. Sequencing the gene would not add any helpful information.

  • C. Again, the child will not have achondroplasia (and hGH is not effective for achondroplasia anyways).

  • D. Families will find their own information. There is no way to prevent or dissuade it.

If a condition is inherited as an autosomal recessive trait. The most likely pathogenetic mechanism would be:

A. Haploinsufficiency.

B. Deficiency of the protein product.

C. Protein interference.

D. Protein suicide.

E. Autoregulatory dysfunction.

B is the correct answer.

  • A. Haploinsufficiency is a mechanism for dominant conditions. Only one allele has to be affected.

  • C. Protein interference is likely to cause dominant disorders.

  • D. Likewise protein suicide will be associated with dominant conditions.

  • E. Autoregulatory dysfunction is a made-up term.

The one-gene, one enzyme hypothesis:

A. is outdated and has no real clinical relevance.

B. is the most common pathogenetic mechanism in human disease.

C. explains some connective tissue disorders.

D. explains some inborn errors of metabolism.

E. explains some homeotic mutants.

D is the correct answer.

  • A. It is not outdated, but has limited applications.


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