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Study Adds Evidence for Inheritability of Dyslexia

October 8, 1987

NEW YORK (AP) _ Scientists today reported new evidence that genetic inheritance can play a role in dyslexia.

Genes appeared to account for about 30 percent of the reading deficit seen in a group of dyslexic children, with the rest due to environmental influences, they said.

Last year, research linked some inherited cases to a genetic defect on chromosome 15, one of 23 pairs of chromosomes that carry genes.

Dyslexia impairs the brain’s ability to process written words, without any defect in intelligence or eyesight. It appears in perhaps 10 percent of school-aged children, although estimates vary.

The new study is reported in today’s issue of the British journal Nature by J.C. DeFries, David Fulker and Michele LaBuda of the University of Colorado in Boulder.

They studied 64 pairs of identical twins and 55 sets of fraternal twins in which at least one of the twins had dyslexia. The average age of the children was about 13.

Identical twins have identical genes, while fraternal twins are no more genetically alike than ordinary siblings. The difference in the two types of twins can be used to study how important genes are in producing various traits.

Analysis of the twins’ scores on reading tests suggests that 30 percent of the overall deficit shown by the dyslexic group was genetic, the researchers wrote.

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