When Mendel crossed two plants that were heterozygous for a single trait, what was the genotypic ratio?

Question

of their offspring?

Answer 1

It's impoprtant that you know here what heterozygous means - it means that the alleles (genes) for the trait were one of each type (as in Rr).  If the alleles were the same (RR or rr), then the parent plants would be homozygous (hetero = different, homo = same).  So you're crossing parents that are Rr x Rr.  Just set up a Punnett square:

___|_R_|_r_|

_R_|___|___|

__r_|___|___|

Combine the letters from each row and colum inside each box (it helps if you always put the capital letter first), then count the number of each type you have:

#RR___ : #Rr___ : #rr___ (this will be your genotypic ratio).  In this case, you should have 1:2:1

If you have to figure a phenotypic ratio, both RR and Rr will give the same trait (if the trait shows complete dominance), so your phenotypic ratio would be:

#RR___ + #Rr___ : #rr___