# 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.

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