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How can I tell if a horse is het Frame?



Screams of the Night


Would this baby be het or hom for Frame?

Frame is otherwise known as Overo (Lethal White) or OLW. The only homozygous (hom) OLW horses in the game as far as I know are Freaky Friday rank specials because homozygous OLW is, as the name indicates, lethal. In reality a foal with two copies of OLW dies soon after birth. In the game, they just don't ever exist at all.

@JustaSaddletramp: You did just fine. Your short post added something that FallenShadow hadn't mentioned, and said things a bit differently. Sometimes, especially with complicated subjects, having more than one explanation worded differently can help someone understand better.

@ GraveDancers: In light of that, here is my contribution to this discussion of Frame, Overo (Lethal White).

1. Frame works in conjunction with other gene mutations that cause white to appear on a horse (Ammit has said, "White means a broken gene.) So, in conjunction with most of the Kit mutations (except roan and tobiano, where the effect is minimal) and the three splash mutations in the game, Frame shifts where the white occurs on the horse, generally allowing pigment along the top and bottom of the horse's body and putting white spots along the sides, so the pigment makes a sort of jagged "picture frame" around the white. This is why it is called "Frame." What is called White Factor in the game, which governs how much white is produced by the broken genes that cause white spotting, is also part of this genetic combination. The greater the white factor, the more white a broken gene will put on a horse.

2. I don't know if you've had or remember having a science class that introduced you to the handy genetic tool called a Punnet Square. This is good for predicting what possible colors/patterns the foal of a given pair of horses might have.

Basically, you draw a largish tic tac board cross hatch. Here's a Punnet Square I made for the potential results of crossing two horses carrying Kit w1.


To make a Punnet Square for the possiblites of a stallion who tests OlwO and a mare who tests OOlw follow this plan:

A. In the top row of the cross hatch, put the sire's gene copies. Put Olw in the middle space and O in the right space.

B. In the left column of spaces, put the dam's gene copies, leaving the top space blank. Put O in the middle space and Olw in the bottom space.

C. Now, in the second row, second column space (middle of the diagram), bring down the sire's Olw and bring the dam's O across, giving OlwO as one possible result for the foal.

D. In the second row, third column space , bring down the sire's O and bring across the dam's O. OO is a second possible result.

E. In the third row, second column space, bring down the sire's Olw and bring across the dam's Olw. OlwOlw is a third possible, and lethal result.

F. In the third row, third column space, bring down the sire's O and bring across the dam's Olw. The fourth possible result is OOlw.

Summarizing the four possible results we see:
one OO, no frame, perfectly safe chance
two OlwO/OOlw, heterozygous frame, also safe chances
One OlwOlw, homozygous frame, definitely lethal chance.

So, if you cross two horses that both carry frame, there is 1 chance in 4 of there being a lethal foal.

3. Why does homozygous frame cause a foal to die after a day or so? Because the gene where this mutation is found is the gene that controls the development of the digestive system, and a break in the gene results in a foal without a complete digestive tract, and as soon as it starts drinking its mother's milk, everything gets backed up and the foal dies from impaction colic, a horrible death. The foal is also born pure white, which is where the phrase Overo (Lethal White) originated.

I hope this isn't more than you wanted to know. The teacher in me took over my fingers. :D

Just one more note here. You can GMT a currently living horse (who is eligible to be GMTd) to have lethal gene combinations. This means you could GMT a horse to be Hom for Frame, or to have the lethal combinations of splash markings (Hom Splash 2, Hom Splash 3, or het for Splash 2 and 3 together).

While I’ve never heard of anyone doing this, it is worth it to remember that it is technically possible to have a Lined Hom Frame horse in this manner.