Plots the genotypes for a set of individuals.  Likely errors are
  indicated by red squares.  In a backcross, genotypes AA and AB are
  indicated by white and black circles, respectively.  In an intercross,
  genotypes AA, AB and BB are indicated by white, gray, and black
  circles, respectively, and the partially missing genotypes "not BB"
  (D in mapmaker) and "not AA" (C in mapmaker) are indicated by green
  and orange circles, respectively.
For the X chromosome in a backcross or intercross, hemizygous males
  are plotted as if they were homozygous (that is, with white and black
  circles).
For a 4-way cross, two lines are plotted for each individual.  The
  left or upper line indicates the allele A (white) or B (black); the
  right or lower line indicates the allele C (white) or D (black).  For
  the case that genotype is known to be only AC/BD or AD/BC, we use
  green and orange, respectively.