Question

Study the below figures that show experiments on transgenic mice. In experiment one, the mice have either a single transgenic copy of A, a single transgenic copy of B, or copies of both A and B. In experiment two, the mice are homozygous for no deletion of gene C(C+/C+), heterozygous for gene deletion (C+/C-), or have double deletion of gene C (C-/C-). a) Of genes A, B, and C, which ones are oncogenes and which ones are tumor suppressor genes? Explain your reasoning. b) What can you infer from the result that mice that are transgenic for both A and B are particularly susceptible to tumors? c) Why do mice that are heterozygous for the gene deletion display lower survival than the C+/C+ controls but much better survival than the homozygous deletion mice? AT ( 20 Eupena 10 ce

Answer 1

A. Since -/- transgenic condition is showing double deletion (or double transgenic) and exhibiting lowest survival as shown in the graph, which suggest oncogenic expression in gene C whereas gene A shows homozygous wild type (+/+) showing maximum survival and it suggest presence of tumour suppressor gene in the mice.

B. Graph suggest that gene B is more susceptible to tumor formation as compared to A which can be evidently seen in the graph for survival of days in mice experiment.

C. Homozygous (C+/C+) is having tumor suppresser gene which inhibit the tumor formation and heterozygous condition is having one deletion (C+/C-) and gene C contain homozygous deletion (-/-) that means there are no tumor suppressor gene which will lead to oncogene expression. Therefore, the order of tumor susceptibility would be C>B>A

C^-/C^- > C⁺/C^- > C⁺/C⁺.