Explain how d option only...
Q.149. In a cross between TtRr × TtRr, total 640 seeds are produced. Find the number of plants produced with first dominant and second recessive traits :-
(1) 106 (2) 300 (3) 240 (4) 120
 

Dear student.

The correct answer is 4. 120.

Phenotypic Ratio of dihybrid cross is
T_R_: 9
T_rr   : 3
ttR_   : 3
ttrr: 1

The question asked is first dominant and second recessive traits, here T_rr is the genotype, that signifies first dominant and second recessive.


The Ratio of progeny with T_rr is 3/16
So the no of seeds with first dominant and second recessive trait= 640*3/16
                                                                                                     =120

Regards.

 

  • 1
What are you looking for?