Familial Trends in Handedness: A study of 30 left handed individuals and their family members

Abstract

Left handedness is seen only in 8-15% of human population but precise cause of it is not known. According to some studies it is inherited while others report no familial correlation. Therefore the present study has been conducted on left handed subjects with the aim to trace the familial correlation of their handedness and if possible to find out genetic basis for left handedness. Present study is a trace back study which was conducted on 30 left handed primary subjects and their family members were considered secondary subjects. Handedness was evaluated using 13 items given by Raczkowski. In 16.7% families left handedness could be traced back to 2-3 more generations. Frank Left handedness was found to be running among 50% (15/30) of the families while among rest 15 families, 60% (9/15) families had one of the parents either ambidextrous or forced right handed. Left, ambidextrous or forced right handedness was more prevalent in mothers as compared to fathers (p = 0.05) and families with affected single parent are significantly higher in comparison to families with both affected parents (p>0.001). On tracing in families, it was observed that both parents were equally transmitting left handedness or ambidexterity to male as well as female offsprings Hence it is concluded that left handedness has strong hereditary correlation, Inheritance is more prevalent in families where both parents are left handed, also has correlation with maternal left handedness and inheritance is X-linked but with autosomal pattern of inheritance.