The woman gave birth to a baby girl with no copy of the gene.

Normally a person would have two copies of the gene.

Then doctors can assume that both parents have one copy of the gene.

His mother has a mutation in one copy of the gene.

You must get a copy of the defective gene from both your parents to have the disease.

The second copy of the gene is often relatively free from selective pressure.

They also looked at mice which only lacked one copy of the gene.

People inherit one copy of the gene from each parent.

These genes are translated faster than they would be if only a single copy of the gene was available.

First, the researchers must breed animals that lack both copies of the gene.