JAMB - Biology (1978 - No. 39)
In a breeding program a cross was made between two true breeding cow-pea types: one with round seeds and the other with wrinkled seed. If roundness is dominant why wrinkleness is recessive, in the first filial generation all the seeds produced will be
25% wrinkled, 75% round
100% wrinkled
50% wrinkled, 50% round
75% wrinkled, 25% round
100% round
توضيح
Owing to the dominance of roundness, the crossing of the two seeds regularly would see all the offsprings having mixed genes but will be round.
Let RR = round seeds while RR = wrinkled seed
In the first filial generation, if we cross RR x rr
We'll have Rr, Rr, Rr, Rr
Remember that RR is dominant while rr is recessive
Therefore, All the four offsprings will be Dominant Round i.e 100% Round