Possible genotypes of children - all Bb
Possible phenotypes of children - all brown-eyed children
|Possible genotypes||= 2Bb : 2bb|
|= 1Bb : 1bb|
|Possible phenotypes||= 2 brown : 2 blue|
|= 1 brown : 1 blue|
This means that about 1⁄2 of the children will be brown-eyed and the other 1⁄2 will be blue-eyed.
If an individual has a dominant phenotype, it is not known what the exact genotype is. For example with the phenotype of brown eye colour, the genotype could be BB or Bb. To find out the genotype of a dominant phenotype, one must cross the individual with the dominant phenotype (e.g. BB or Bb) with an individual with the recessive phenotype (e.g. bb). If the offspring all have the dominant phenotype (e.g. brown eyes), then the parent was pure-bred (e.g. BB). If the offspring have any with the recessive phenotype, then the parent was hybrid (e.g. Bb).
Possible genotypes = 1 BB : 2 Bb : 1 bb
Possible phenotypes = 3 brown : 1 blue
This means that 3⁄4 of the children will be brown-eyed, and 1⁄4 will be blue-eyed.