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Originally Posted by mommadog1  Then erect ears are a dominate trait, and would dominate over floppy ears. So how can a recessive trait show up over a dominate? As far as I know it can't.  |
Probably over-simplifying here, but, with a recessive gene, an offspring must get a copy of that gene from each parent in order to be expressed. With a dominate gene, only one copy of that gene is needed for a trait to be expressed.
" There are 3 genotypes for every trait:
1. Double Dominant or pure for a character =Double Homozygous
2. Double Recessive or pure for a character = Recessive Homozygous
3. Mixed genes or hybrids = Heterozygous "
The above taken from Ann Seranne's 'The Joy of Breeding Your Own Show Dog'.
As you can see, breeding pure for a trait means to be homozygous. An animal that is heterozygous for a trait may give you that trait, but not predictably. In the case of the Yorkie, Huddersfield Ben is considered the foundation stud because he was the first to breed pure but probably wasn't the first to exhibit the desired traits.
Also, a gene being recessive doesn't mean it's a 'bad' gene. A great many features of the Yorkshire Terrier come from recessive genes.
I recommend Seranne's book. It's a good place to start with dog genetics. You'll get more from it the more you go back to it.