Descendants bred to have two defective copies of the Clock gene, one from each parent, had a daily rhythm four hours longer than normal.

Most people with inherited metabolic disorders inherit two defective copies of the gene - one from each parent.

Both parents are "carriers" of the bad gene, meaning they carry one defective copy and one normal copy.

An English family with a severe, heritable language dysfunction was found to have a defective copy of this gene.

For decades, only defective copies were available.

The substitute leaf was taken from a defective copy of volume two, which was being broken up for sale in parts and leaves.

About 5 to 10 percent carry two defective copies and therefore make a defective version of the enzyme.

Each virion contains a full length copy, or defective interfering copies.

Prenatal testing seeks to determine whether the fetus has inherited two defective copies, one from each parent.

The gene for the allergen will be knocked out by replacing it with a defective copy.