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DeafBlind Cajuns


Phyllis Baudoin Griffard
Department of Biology
University of Louisiana at Lafayette


This modular case study tells the story of Dan and Annie, a married couple of Acadian ancestry who have a genetic form of deafblindness called Usher syndrome. They live in Southwest Louisiana, home of the largest population of DeafBlind citizens in the United States. Acadian Usher syndrome is caused by an allele of the USH1C gene that came to Louisiana with the first Acadian settlers from Canada who founded today’s Cajun population. This allele’s single nucleotide substitution creates an erroneous splice site that produces a defective cytoskeletal protein (harmonin) of the cochlear and vestibular hair cells and retinal photoreceptors. This splice site is the target of a promising gene therapy. The case study applies and connects Mendelian inheritance, chromosomes, cell division, vision and hearing, DNA sequences, gene expression, gene therapy and population genetics to a specific gene and its movement through generations of Dan and Annie’s families.  After the introduction, each of the remaining sections can be used independently either for in-class team activities or out-of-class extensions or assignments over an entire year of introductory undergraduate biology.


  • Apply the general understanding of genetics, gene expression, cell biology and neuron function to the special case of Usher syndrome, a genetic deafblindness in the human population of Acadian descent.
  • Apply concepts of Mendelian inheritance and gene expression to explain how a single nucleotide substitution can lead to a complex human condition such as Acadian Usher syndrome (deafblindness), sickle cell disease or others.
  • Apply the Hardy-Weinberg equation to a real population genetics problem.
  • Calculate allele and genotype frequencies in given populations and use these to predict whether a population is evolving.


Genetics; hearing; vision; deaf; blind; mitosis; meiosis; population genetics; gene expression; deafblindness; Usher syndrome; Louisiana, Acadian; cajun; disability

Topical Areas


Educational Level

Undergraduate lower division


PDF, Word

Type / Methods

Directed, Discussion, Modular



Subject Headings

Biology (General)  |   Genetics / Heredity  |   Molecular Biology  |  

Date Posted


Teaching Notes

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Supplemental Materials

The Word document below is used in Part V of the case and should not be printed until students have edited the included sequence according to instructions.


Answer Key

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