Question

A true-breeding plant with green pods and wrinded seeds is crossed with a plant that is heterozygous for both traits. Drawa

Answer 1

The possible genotype would be when one of the parent is homozygous dominant -    Phenotype ratio= 16:0,  genotype ratio= 1 YYRR : 1YYRr: 1 yYRR: 1 YyRr.

when one of the parent is homozygous recessive the phenotype ratio is 4 yellow and round : 4 yellow and wrinkle : 4 green and round : 4 green and wrinkle and genotype ratio = YyRr:  Yyrr: yyRr: yyrr  or

1:1:1:1   genotype ratio.

Explanation:

The data given:

yellow and round dominant ---  Y R

Green and wrinkle recessive ---- yr

It is given a true breeding plant, which means the parent plant is homozygous for the trait. Let one of the parent be YYRR

Also it is given that it was crossed with heterozygous parent so the other parent be YyRr

The cross between them is shown in punnet square as:

       YR        Yr          yR           yr

YR  YYRR   YYRr    yYRR     YyRr

YR   YYRR   YYRr    YyRR    YyRr

YR   YYRR   YYRr    YyRR    YyRr

YR   YYRR   YYRr    YyRR    YyRr

4 YYRR: 4 YYRr: 4 YyRR: 4 YyRr

thus genotype ratio is 1:1:1:1

phenotype ratio all 16 are yellow and round.

In case when either parent is homozygous recessive is crossed with heterozygous parent. The punnet square for this is shown as:

yyrr X YyRr

      YR        Yr        yR      yr

yr YyRr     Yyrr     yyRr   yyrr

yr YyRr     Yyrr    yyRr    yyrr

yr YyRr     Yyrr   yyRr     yyrr

yr  YyRr     Yyrr  yyRr     yyrr

4 YyRr: 4 Yyrr: 4yyRr: 4yyrr

1:1:1:1   genotype ratio

phenotype ratio =  4 yellow and round : 4 yellow and wrinkle : 4 green and round : 4 green and wrinkle.

Thus phenotype ratio is 1:1:1:1