why are recessive genes more common than dominant genes? Like widows peak is not common but dominant?

Answer 1

The gene for widow's peak is dominant, but not many people have this gene. Most people have the gene for a straight hairline, so that's what gets passed on.

Just think about taking one pencil from each of the first two people who come through the door into your biology class. The teacher has it planned so that each biology student has two pencils. Most of the pencils are the plain, yellow, put-them-in-the-sharpener variety. But 8 out of the 30 biology students have bright red mechanical pencils. What are the chances that you will get one of the bright red pencils by taking one pencil from each of the first two people who come through the door? Even if one of those two people has a red pencil, you might get his other pencil -- the yellow one.

So, if the allele for widow's peak is not very common (kind of like the red pencils), then most offspring won't get a copy of that gene. Doesn't matter if it's dominant or not -- there just aren't that many of them out there.