You may ask, what does probability have to do with Genetics? Actually it does alot. Probability is the likely hood of
a certain trait occurring. For example, if you take a brunnette woman (i.e. BB) and a blond haired man
(i.e. bb), chances are the union of the two would produce all brunnette and the offsprings would be heterozygous.
To figure that out, you must use a Punnett Square, which is a diagram.
Step One: Label the couple's alleles on top and on the side:
Step Two: You then take the top letter and the letter to the left and put them in the same box:
Step Three: Fill in the three remaining boxes:
Since the dominant allele pair must be BB or Bb, all the offspring will be brunnette. Since
there is one lowercase and uppercase letter, they will all be heterozygous!