My interpretation of your requirement is not quite the same as @teylyn’s (though hers makes more sense to me!) Say your ‘Yes, No’ list is in F1:F2
and you require to validate from Row1 onwards:
Select B1
Data > Data Tools – Data Validation, Data Validation, for Allow: choose List, and under Source: enter:
=IF(ISBLANK(A1),,F$1:F$2)
Click OK and copy B1
down as far as required.