>>>>Erm, if you breed two horses and the stallion is solid, that results in only a 25% chance of the foal inheriting sabino. If the mare is heterozygous for sabino then she is going to be n/Sb as opposed to Sb/Sb (homozygous). The stallion will be n/n for sabino. Out of four possibilities, only one results in sabino, giving you a 25% chance of her passing it on when bred to a non-sabino stud.
If the stud is also n/Sb then you have two out of four genes being sabino and a 50% chance. Load it into the quadrant.
You are mistaken. If the mare is SB/n and the stallion is n/n, it **is** 50%, since the mare will pass her Sb 50% of the time, or her n 50% of the time.... and the stud will pass his n all the time.
Here is a rough square-- mare is Sb/n horizontal entry, stud is n/n vertical entry---the four quadrant shows Sb/n, n/n, Sb/n,n/n... so 50/50.
...........Sb.....n
----------------------
...n..|..Sb/n..n/n
...n..|..Sb/n..n/n
If both parents are heterozygous Sabino, the odds of getting sabino rise to 75%-- 50% heterozygous and 25% homozygous--
...........Sb........n
----------------------------
.Sb..|..Sb/Sb..Sb/n
...n..|..Sb/n.....n/n
Sorry about all the ..... I am using them as placeholders, because the posting program ignores the spaces I try to put in, LOL