Q1. Hypophosphatemia (vitamin D-resistant rickets) is inherited as the sex-linked dominant trait. The relevant gene is found on an X chromosome. What is an expected outcome of a cross between a homozygous recessive woman and a man with hypophosphatemia?
Q2. A chimeric gene containing a cloned cDNA of the coat protein (CP) gene of tobacco mosaic virus (TMV) was introduced into tobacco cells on a Ti plasmid of Agrobacterium tumefaciens from which tumour inducing genes had been removed. Plants regenerated from transformed cells expressed TMV mRNA and CP as a nuclear trait. Seedlings from self-fertilized transgenic plants were inoculated with TMV and observed for expansion of disease symptoms. The seedlings that expressed the CP gene were delayed in symptom development and 10 to 60 percent of transgenic plants failed to develop symptoms for the duration of the experiments. Increasing the concentration of TMV in the inoculum shortened the delay in appearance of symptoms. The results of these experiments point to that plants can be genetically transformed for resistance to virus disease development.