question_answer

Phenotypic of Downs syndrome increases when the maternal age is

A)  3:.1             

B)  1 :1

C)  1:2: 1           

D)  2: 1  

Correct Answer: B

Solution :

 Monohybrid test cross is cross between a hybrid dominant for one gene and recessive homozygous individual, e.g., Rr and rr. Thus, the phenotypic ratio is 1:1.