Table Creation Process
- Determine all the 2-gene combinations for each parent. This is determined by making all the different combinations of one Black/brown Gene 1 and one Dense/dilute Gene 2 that can occur from the 4-genes of the parent. The table below shows the combinations for each unique type.
- Create a matrix using all
parent combinations.
Children cells = # of Parent A combinations x # of Parent B combinations
- Put Parent A 2-gene combinations in the header cells horizontily on top and Parent B 2-gene combinations in the header cells vertically on the left.
- 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.
- Figure out the color of each child combination. Remember Bb is the same as bB and Dd is the same as dD. Order is not important in this case, although usually I put the dominant (uppercase) allele first.
- Calculate the percentage of each color.
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 |
Example:
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).- 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. -
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
- 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
- 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.
- 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