| Date | November 2015 | Marks available | 1 | Reference code | 15N.1.HL.TZ0.35 |
| Level | Higher level | Paper | Paper 1 | Time zone | TZ0 |
| Command term | Question number | 35 | Adapted from | N/A |
Question
In a fruit fly experiment, grey body, normal winged (homozygous dominant) fruit flies were mated with black body, short winged (homozygous recessive) fruit flies. The F1 dihybrid females were then used in a test cross. If the genes are always linked and no crossing over occurs, what would be the predicted ratio in the F2 generation?
A. 9 : 3 : 3 : 1
B. 1 : 1 : 1 : 1
C. 3 : 1
D. 1 : 1
Markscheme
D
Examiners report
This question proved to be too difficult for many candidates and was a poor discriminator. Many candidates just guessed the answer.
