AFRMA

American Fancy Rat & Mouse Association

This article is from the Winter 1997 AFRMA Rat & Mouse Tales news-magazine.

Rat Genetics - The WHAT IF chart

By Nichole Royer


What will I get if I breed this rat to that one? This is a question I hear frequently. Quite often the people asking it have no particular background or interest in genetics and simply want to know what the likely outcome will be. I was asked at one of our recent shows if there was a way to look up what different color combinations will produce, without understanding genetics. This got me wondering, and gave birth to the “What If” chart.

The charts on the following pages are an oversimplification of a rather complicated concept. Despite this, they can be a simple to use, useful tool. The major thing to understand is that they represent what should and could happen, not what will happen. They are not an absolute, just a guide.

How does it work?

Find the color of your male rat at the top of the chart. Find the color of the female along the left hand side. Draw lines down the column from the male’s color, and across the row from the female’s. Where they intersect, is the color you should get in the litter.

If you know the background behind one or both of the rats in question, you can take this one step further. First draw lines for your male and female. Next find the color of your male’s parents along the top of the chart and draw lines down their columns. Do the same for the female’s parents down the left side. This gives you six lines on the chart. Anywhere any two of the lines intersect is a color you could get by breeding your male and female.

Problems with the “What If” chart

In including the potential grandparents, this chart does not take into account dominant genes. For instance, if you breed together two blacks, one of whom had an Agouti parent, the chart will tell you that you could get Agouti babies. You won’t! The colors on this chart can be broken down into two groups. Everything from Agouti to Cinnamon Pearl is in the Agouti group. Everything else is in the Black group. When you breed together two animals from the Black group, you will never get any of the Agouti group colors.

The other major problem with the “What If” chart is that it does not take into account the combining of two recessive traits. For instance, if you breed together two Blacks which both have a Seal Point Siamese and a Blue parent, the chart says that you should get Black, Blue, and Seal Point Siamese babies. This is true, however, it does not tell you that you will also get Blue Point Siamese.

Needless to say, this system for predicting potential outcome from a breeding is neither precise, nor decisive. As I said, it is simply a useful tool which assumes that the rats in question are not carrying any hidden traits (recessive genes). Most of our rats are carrying other colors; therefore, you can expect to get other colors in addition to the ones this chart predicts. These can be considered “lucky surprises.”

For anyone who would like to know in more detail what their litters will produce, I highly recommend learning more about genetics. It is an extremely interesting subject, and well worth most breeders time to learn.

Click HERE for the WHAT IF chart

NOTE: The WHAT IF (color) two-page chart is actually one chart which has been split in half due to space limitations. Those boxes which contain more than one color means that any (all) of those colors could be expected. The coat and body type charts below work the same way the color chart does.
M/L=Mink/Lilac, SP=Seal Point, PE=Pink-Eyed. *

COATS STANDARD REX SATIN HAIRLESS
STANDARD STANDARD REX/STANDARD STANDARD STANDARD
REX REX/STANDARD REX/STANDARD/
POOR HAIRLESS
REX/STANDARD REX/STANDARD
SATIN STANDARD REX/STANDARD SATIN STANDARD
HAIRLESS STANDARD REX/STANDARD STANDARD HAIRLESS

BODY TYPE NORMAL ODD-EYE TAILLESS
NORMAL NORMAL NORMAL NORMAL
ODD-EYE NORMAL NORMAL / A FEW ODD-EYES NORMAL
TAILLESS NORMAL NORMAL NORMAL / A FEW TAILLESS

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Updated February 24, 2014