Theory question 106
Basic Genetics(a) Define crop improvement.
(b) Copy and complete the Punnett square (gametes TC, Tc, tC, tc on each side) based on Mendel's Law of Independent Assortment of Genes (Dihybrid inheritance), where T = Tall, C = Coloured, t = Dwarf, c = White, T and C dominant.
(c) Calculate the percentage of plants in 6(b) above that are: (i) Tall coloured; (ii) Tall white; (iii) Dwarf coloured; (iv) Dwarf white.
Show the model answer
(a) Crop improvement is the development of better crop varieties (higher yield, quality, resistance) through introduction, selection, breeding and other methods
(b) Rows TC: TTCC, TTCc, TtCC, TtCc; Tc: TTCc, TTcc, TtCc, Ttcc; tC: TtCC, TtCc, ttCC, ttCc; tc: TtCc, Ttcc, ttCc, ttcc
(c) Ratio 9 : 3 : 3 : 1 out of 16: (i) tall coloured 9/16 = 56.25%; (ii) tall white 3/16 = 18.75%; (iii) dwarf coloured 3/16 = 18.75%; (iv) dwarf white 1/16 = 6.25%
Fill all 16 boxes, then count phenotypes.