∞ generated and posted on 2016.08.28 ∞
Means of inferring the genetics associated with a phenotypic character based on existing family relationships rather than experimental crosses.
Pedigree analysis is a way around both ethical and practical issues involved in the analysis of human Mendelian genetics. That is, in situations where both time and propensity precludes experimentation, then one is limited to considering those "experiments" that have already been "performed", that is, what already exists within the world around us.
This is very much the case in more "historical" sciences such as evolutionary biology and geology. In the case of pedigree analysis, though, it can be truly historical documentation that is relied upon, i.e., records concerning aspect of ancestor phenotypes, at best, or at least records which indicate how descendants are related.
The following video does a nice job of walking through a single pedigree, considering autosomal dominant versus autosomal recessive and sex-linked traits such as sex-linked recessive:
The following video also does a nice job of walking through a single pedigree, considering autosomal dominant versus autosomal recessive and sex-linked traits such as sex-linked recessive, but with an important twist:
And this is my own little pedigree:
Figure legend: So, just what is my eye color genotype? With grandfather's eyes, paternal aunt's eyes, and daughter's eyes all blue, it seem fairly certain that my grandmother, father, and myself all carry or carried a blue allele as well. My father and I presumably share the same blue allele that my daughter now carries as half her complement, while my father's brown came from his mother (and thus her blue is found in my aunt but not my father nor myself). The fact that a maternal aunt has blue eyes, however, complicates this story. My mother, brother, son, and myself, on the other hand, share green hazel eyes, all presumably traceable to my mother, or is it just the tendency to "hazel out" that can be traced to her? Note that circles are female, squares are males, horizontal lines between symbols indicate successful matings (which in this case I'm assuming are synonymous with marriages), and vertical lines (along with horizontal branchings) connect direct ancestors to direct descendants.