(a) Define crop improvement. [2 marks] (b) Copy and complet the table below based on Mendel's Law of Indepen-dent Assortment of Genes (Dihybrid inheritance)...
Question 1 Report
(a) Define crop improvement. [2 marks]
(b) Copy and complet the table below based on Mendel's Law of Indepen-dent Assortment of Genes (Dihybrid inheritance).
| TC | Tc | tC | tc | |
| TC | TTCC | |||
| Tc | Ttcc | |||
| tC | ttCc | |||
| tc | ttcC |
Use the following information: T = Tall; C = Coloured; t = Dwarf; c = White. (Where T and C are dominant character; while t and c are recessive TC TTCC characters) [6 marks]
(c) Calculate the percentage of plants in (b) above that are: (i) Tall coloured; (ii) Tall white; (iii) Dwarf coloured; (iv) Dwarf Tc Ttcc white [8 marks]
Answer Details
(a) Crop improvement is the application of genetic and agronomic principles (selection, hybridization, mutation and modern biotechnology) to produce new or better crop varieties that possess desirable qualities such as high yield, early maturity, resistance to pests and diseases, and improved nutritional or market quality.
(b) Completed dihybrid Punnett square for the cross TtCc \( \times \) TtCc (gametes TC, Tc, tC, tc):
| TC | Tc | tC | tc | |
|---|---|---|---|---|
| TC | TTCC | TTCc | TtCC | TtCc |
| Tc | TTCc | TTcc | TtCc | Ttcc |
| tC | TtCC | TtCc | ttCC | ttCc |
| tc | TtCc | Ttcc | ttCc | ttcc |
Counting the 16 offspring gives the classic dihybrid ratio 9 : 3 : 3 : 1: 9 Tall coloured (T_C_), 3 Tall white (T_cc), 3 Dwarf coloured (ttC_) and 1 Dwarf white (ttcc).
(c) Percentage of each phenotype (each box represents \( \frac{1}{16} \) of the plants):
- (i) Tall coloured = \( \frac{9}{16}\times100 = 56.25\% \)
- (ii) Tall white = \( \frac{3}{16}\times100 = 18.75\% \)
- (iii) Dwarf coloured = \( \frac{3}{16}\times100 = 18.75\% \)
- (iv) Dwarf white = \( \frac{1}{16}\times100 = 6.25\% \)
Download The App On Google Playstore
Everything you need to excel in your exams
