Question

Mendelian ratios are modified in crosses involving autotetraploids. Assume that one plant expresses the dominant trait green seeds and is homozygous (WWWW). This plant is crossed to one with white seeds that is also homozygous (wwww). If only one dominant allele is sufficient to produce green seeds, the F1 phenotypic ratio will be all green. Predict the phenotypic ratio of the F2 generation.

Answer 1

35 : 1

Step-by-step explanation:

WWWW plant will produce all WW gametes and wwww plant will produce all ww gametes. When WWWW X wwww :

WWww (F1) = All green since one dominant W is enough to produce green color.

When WWww X WWww :

Gametes will be produced by them in 1:4:1 ratio ( WW : Ww : ww ) because each W can pair with two w so two W will give total of four Ww combinations.

1WW 4Ww 1ww

1WW 1WWWW 4WWWw 1WWww

4Ww 4WWWw 16WWww 4Wwww

1ww 1WWww 4Wwww 1wwww

Out of the total 36 progeny, only 1 has wwww genotype which has not a single dominant W allele so it will be white in color. Thus, in F2 generation the phenotypic ratio will be 35 (green) : 1 (white).