What is the most common genetic abnormally?

[Andrew Goldfinger]

In article
<Pine.A41.3.95b.970616104123.22810B-100000 at dante27.u.washington.edu> Ryan
Maves, smithers at u.washington.edu writes:
>On 16 Jun 1997, Andrew Goldfinger wrote:
>
>> >>What is the most common genetic abnormally?
>> 
>> Lactose intolerance?
>
>Hard to call it an abnormality, since more people worldwide have it than
>don't. 

Lack of lactose intolerance?