Tragic genetic riddle solved for Texas families

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<http://www.statesman.com/news/content/news/stories/local/01/11/0111fatalgene.ht\

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> A team of scientists in the United States and Germany said it has

> discovered the gene that caused the rare disease — known as X-linked

> infant spinal muscular atrophy — that killed and three sons of

> Ann Messer's cousins. It was announced in a paper published Thursday

> in The American Journal of Human Genetics.

>

> The X-linked form is the most severe type of spinal muscular atrophy,

> The more common form of spinal muscular atrophy is believed to

> affect one in 6,000 births, she said. She identified 16 families

> worldwide with the X-linked variety, including the Messers and Ann

> Messer's cousins, who joined the study. She said it's possible that

> many of the 4 percent of the babies born with spinal muscular atrophy

> might actually have the X-linked form.

>

> Because the defective gene is recessive and on the X chromosome, the

> disease can be passed on only to boys, who inherit the X chromosome

> from their mothers and a Y chromosome from their fathers. Girls, who

> have two X chromosomes, can carry the defective gene but won't

> develop the disease, Baumbach-Reardon said.