Table Creation Process

Possible 2-gene combinations from each type of parent:

4-Genes Notation Color Type 2-gene Combinations
BBDD Nat. Natural not carrying brown or dilute BD
BbDD Nat(b) Natural carrying brown BD, bD
BbDd Nat(d) Natural carrying dilute BD, Bd
BbDd Nat(bd) Natural carrying brown & dilute BD, bD, Bd, bd
BBdd Blue Blue not carrying brown Bd
Bbdd Blue(b) Blue carrying brown Bd, bd
bbDD Champ. Champagne not carrying dilute bD
bbDd Champ(d) Champagne carrying dilute bD, bd
bbdd Plat. Platinum bd


This example calculates the probabilities when mating a Natural carrying both brown and dilute alleles Nat(bd) to a Blue carrying a brown allele Blue(b).
  1. Obtain the 2-gene parent combinations from the above table.

    Parent A - BbDd Nat(bd) combinations: BD, bD, Bd, bd.
    Parent B - Bbdd Blue(b) combinations: Bd, bd There will be 8 children cells.

  2. Create a matrix of all parent combinations. There will be 8 children cells.
      Parent A BD Parent A bD Parent A Bd Parent A bd
    Parent B Bd        
    Parent B bd        

  3. Add the parent combinations together for a 4-gene combination and put them in each cross inner cell to create the resulting possible children combinations. Put the Gene 1s together and the two Gene 2s together.
      Parent A BD Parent A bD Parent A Bd Parent A bd
    Parent B Bd BBDd bBDd BBdd bBdd
    Parent B bd BbDd bbDD Bbdd bbdd

  4. Figure out the color of each child combination.
      Parent A BD Parent A bD Parent A Bd Parent A bd
    Parent B Bd BBDd Natural bBDd Natural BBdd Blue bBdd Blue
    Parent B bd BbDd Natural bbDD Champagne Bbdd Blue bbdd Platinum

    Remember that BdDd is the same as bBDd. I usually write the dominant (uppercase) allele first regardless of whether it came from the horizontal or vertical cells. In this example, I always put Parent A's allele first, so I could illustrate that the order of the two alleles (withinin each set of Gene 1s and Gene2s) is not important. BdDd and bBDd are the same. Putting the dominant allele first just makes it easier to recognize the colors.

  5. Since there are 8 possible results, each results represents a probability of 1/8. Adding up the number of occurrences you get the following probabilities:
    • Natural 3/8
    • Blue 3/8
    • Champagne 1/8
    • Platinum 1/8