Assume that in pea plants yellow and smooth are dominant and unlinked (independent) traits. If a green, homozygous smooth plant is mated with a plant that is heterozygous for both traits, what fraction of the offspring can be expected to be both yellow and smooth

1/2 or 0.5

Explanation:

Given,

yellow (Y) is dominant over green (y)

smooth (S) is dominant over wrinkled (s)

Plant 1 : green, homozygous smooth = yySS

Plant 2 : heterozygous for both traits = YySs

When yySS X YySs :

        YS      Ys       yS       ys

yS  YySS   YySs   yySS   yySs

Out of the possible 4 combinations, YySS and YySs will be both yellow and smooth. Hence 1/2 or 0.5 fraction of offspring can be expected to be both yellow and smooth.