A long-haired cat (recessive trait s) is crossed with a heterozygous short-haired cat (dominant trait S). What percentage of their offspring will have long hair?
The best way to see this is to simply draw a punnett square. As you've said, let's call
As you can see, out of the 4 possible outcomes, 2 will result in short hair, and 2 in long. So, you'd have a
Remember: each side of the punnett square represents all possible gametes that each parent can provide. In this case, the long haired cat can only contribute a long haired allele (
There's no way of telling which will happen, but the punnett square tells us all the possibilities of what could happen.
If you're having trouble with this concept, here's two great videos by Bozeman Science that can help:
Hope that helped :)