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?

1 Answer
Nov 21, 2017

50%

Explanation:

The best way to see this is to simply draw a punnett square. As you've said, let's call $S$ the dominant trait (short hair) and $s$ the recessive trait (long hair):

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 color(blue(50%)) chance of getting a short haired cat.

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 ($s$), while the short haired cat can contribute either a short haired allele ($s$) or a long haired allele ($S$).

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 :)