The fidelity of translation is dependent on the reliable action of aminoacyl tRNA syntheta...

The fidelity of translation is dependent on the reliable action of aminoacyl tRNA synthetases that ensure the association of only one type of amino acid with a specific tRNA. Two relatively rare human conditions, Charcot-Marie-Tooth disease 2D (CMT2D) and distal spinal muscular atrophy type V (dSMA-V), are neuropathologies of the peripheral axons that map to a well-defined region of the short arm of chromosome 7, as does the gene for glycyl tRNA synthetase. Families with CMT2D or dSMA-V have been identified with missense mutations in the gene for glycyl tRNA synthetase; and the mutations present in CMT2D and dSMA-V have been found to result in a loss of activity of glycyl tRNA synthetase (Antonellis et al., 2003). A sample pedigree (from Antonellis et al., 2003) is presented here (to maintain anonymity, sexes are not provided).

(a) Considering the following pedigree and the function of aminoacyl tRNA synthetases in general, would you conclude that the genes causing these diseases are dominant or recessive in their action?

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(b) Considering the vital role that synthetases play in protein synthesis, speculate as to how individuals might survive with such a defect in translational efficiency.

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(c) Why might some tissues (neural) be more affected than others?