We learn a lot from pedigrees

February 22nd, 2009 by admin | Filed under cardiac.

Many of our research projects are genetic studies. In some cases, we are studying pedigrees of animals with heart disease to determine the mode of transmissionof a trait (or how a trait is inherited). There are a few common “modes” including X-linked, Autosomal recessive and Autsomal dominant.

X-linked traitsare those in which the diseaseor defect may be seen morein males than females and females can be silent carriers. There is some evidence that dilated cardiomyopathy (DCM) in the Great Dane is inherited this way (at least in some familes).Since femalescan be silent carriers and males tend to show thetrait, itmayfirst seem thatthe trait is passed from the father, but it actually came from the mother who was a silent carrier.

Other forms of cardiomyopathy in the dog including Boxer ARVC and Doberman pinscher Dialted Cardiomyopathy,as well as Hypertrophic cardiomyopathy in the cat are autosomal dominant traits. In these cases,males and females are generallyequally affected andevery affected individual should have at least one affected parent. The trait should show up in every generation.

Geneticists generally studythe informationfrom the animal's pedigree by putting it into a pedigree drawing in whicheach animal is represented as a circle or a square.Traditionally, affected animals arerepresented by black symbols andunaffected animals are represented by white symbols.Male animalsare represented by squares and females by circles. The attached pedigree drawing is from a family of Doberman pinschrers with dilated cardiomyopathy. One can see 4 affected males (black squares) and 4 affected females (black circles).