IB Biology Practice Test 6

A student investigated the inheritance of two genes in tomato (Solanum lycopersicum): stem colour (purple, allele A, dominant to green, a) and leaf shape (cut, allele C, dominant to potato-leaf, c). True-breeding purple-stemmed, cut-leaved plants were crossed with true-breeding green-stemmed, potato-leaved plants, and all F1 plants had purple stems and cut leaves. F1 plants were self-pollinated and 320 F2 seedlings were grown in the same compost, light and temperature and scored three weeks after germination. Null hypothesis: the four F2 phenotypes occur in a 9 : 3 : 3 : 1 ratio.