Connor inherited Duchenne Muscular Dystrophy from his mum
Genetic conditions with an X-linked recessive pattern of inheritance usually only affect boys. This is because they are caused by an altered gene carried on the X-chromosome.
Girls have two copies of the X-chromosome (XX), so if there is an alteration in a gene on one of them, the working copy on the other can usually compensate.
Boys, by contrast, only have one copy of the X-chromosome (XY), so if they inherit just one altered gene they will be affected.
Duchenne Muscular Dystrophy is an X-linked recessive condition. It causes progessive muscle weakness and starts to affect boys when they're just toddlers.
Watch Connor's Story to see what life is like with this debilitating condition ยป
X-linked inheritance
Photo: US National Library of Medicine