What the heck does it mean when a biology book, teaching heredity, speaks of a pedigree, or pedigree trait? An example is given of a Virginia family in which some offspring have webbed fingers (kinda like siamese fingers). It is a pedigree trait, but the book never bothers to define “pedigree traits”. What is this? Inbreeding? Do they have AKC papers? (ha-ha) 
Pedigrees are simply family tree type diagrams used to determine the inheritence patterns of traits (hence pedigree traits) across a large number or long time frame of a set of relatives.
Here’s a large example.
A rather famous example is hemophilia among European royal families.[
In this case, it means that the trait has been traced through several generations of a family, each individual possessing it or not having been recorded in a pedigree. So, in a sense, these families do have papers–but the papers are part of genetics research.
Jk1245, my problem with these trees is that the 1st generation will show the parents, the 2nd generation shows the offspring, but…there’s always a link between two offspring suggesting an inbreeding!
In your link, for example, the 1st generation shown is the offspring, but we see a cross-tie between two circles and one square! What the heck is that? (It doesn’t say it, but the square is usually male, and the circle is for female.) Maybe I am mis-reading the tree, but I cannot see any other meaning here esp. when a vertical line comes off each horizontal line indicating the two mated (by the horizontal line) and had offspring (indicated by the vertical line).
Very poorly explained in most biology books, by the way…
They were from Arkansas.
If you trace your family history back a couple of hundred years, you may well find at least one limb on your tree where 2nd or even first cousins marrying. It was more practice than taboo back then.
You mean the (one of several) double diagonal lines that occurs somewhere in the XXX generation? That means there was a first/second cousin marriage, and the resulting daughter(second circle). The double lines indicate inbreeding.
The pedigree in question is of royalty, who are probably more prone to inbreeding than the general population. Regardless, if you trace your lineage back far enough, you’ll find out that you’re probably your own cousin five times removed on your mother’s side and six times removed on your father’s side. My mother keeps an extremely long scroll (for want of a better word) on which is diagrammed out our ancestors all the way back to the 1700’s. My immediate family appears four or five times, as distant branches of the the family would get married. And that’s just on my mother’s side. My father’s side is even more prolific, and I shudder to think what my father’s pedigree looks like. (No, we’re not from Arkansas.)