Observe the following cross between tall plants having round seeds and dwarf plants having wrinkled seeds. The individuals obtained in the F1 -generation were thereafter self-crossed.
TTRR X ttrr
(Tall, Round) (Dwarf, Wrinkled)
TtRr X TtRr (F1 -generation self-crossed)
(Tall, Round) (Tall, Round)
1. What would be the phenotypes of the individuals obtained in the F2-generation? Give their ratios.
2. Why do you think all the individuals of the F1-generation were tall with round seeds?
3. What will be the number of progenies obtained in F2-generation in a dihybrid cross with pure dominant traits?
4. What would be the phenotype of the individual obtained in F1 -generation?
Answers
Answer:
Correct option is D)
As we know that tallness (T) is dominant over dwarfism (t) and round seed (R) is dominant over wrinkled (r).
Parent Generation, P
1
: TTRR x ttrr
F
1
generation : TtRr (tall plant, round seed)
P
2
generation : TtRr x TtRr
Gametes TtRr --->
TtRr TR Tr tR tr
TR TTRR
(tall plant, round seed)
TTRr
(tall plant, round seed)
TtR
R
(tall plant, round seed)
TtRr
(tall plant, round seed)
Tr TTRr
(tall plant, round seed)
TTrr
(tall plant, wrinkled seed)
TtRr
(tall plant, round seed)
Ttrr
(tall plant, wrinkled seed)
tR TtRR
(tall plant, round seed)
TtRr
(tall plant, round seed)
ttRR
(dwarf plant, round seed)
ttRr
(dwarf plant, round seed)
tr TtRr
(tall plant, round seed)
Ttrr
(tall plant, wrinkled seed)
ttRr
(dwarf plant, round seed)
ttrr
(dwarf plant, wrinkled seed)
Thus, dwarf plant, wrinkled seeded progeny (ttrr) in F
2
generation= 1/16; D is correct answer.