This is either because they cause no change in the composition of the protein that the gene encodes (some apparently different genetic words actually have the same meaning to the protein-making apparatus), or because the change they make has no effect on the protein's function.

ECONOMIST: Genetics gets more complicated

Working with the geneticists' favourite animal, the fruit fly Drosophila, Dr Gibson has pinpointed a series of so-called cryptic variations that have no effect on a protein's structure, but can nevertheless, if the circumstances are right, have a significant effect on the individual they belong to.

ECONOMIST: Genetics gets more complicated

Less than three weeks ago I revisited my own gluten intolerance and cut out all grains and milk (milk contains a gluten-like protein cassein which has an equally bad effect on me).

FORBES: If You Want To Lose Weight, Check What You Can Eat

In osteoporosis the RANK ligand protein is all too effective in producing the breakdown effect, resulting in debilitating hip fractures in postmenopausal women and others.

FORBES: Biotech Behemoth

The flavonoids inhibited the secretion of various inflammatory cells called cytokines in H5N1-infected cells, but had no effect on noninfected cells or tumor necrosis factor, a key inflammatory protein.

WSJ: Sleep's Surprising Effects on Hunger

They are, in effect, internal viruses unable to leave a cell because they lack the protein coats that allow real viruses to survive in the outside world and attach themselves to new host cells, but contributing nothing to the welfare of the cells they inhabit.

ECONOMIST: The first complete DNA sequence of an animal is now in the bag