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 »
X-linked inheritance
Photo: US National Library of Medicine