Close-up image of a cat's face

Whose gene is it anyway?

Genes are widely shared but adapt to take on new roles in different organisms

To build a fruit fly, you need (among other things) a set of genes known as Hox genes. These are ‘master control’ genes that coordinate the activity of many other genes, so a head, abdomen, legs, antennae and all the other bits of a fly are built in the right place.

You need essentially the same genes to build a cockroach. Or a bumblebee, a frog, a mouse or a human being.

You need essentially the same genes to build a cockroach. Or a bumblebee, a frog, a mouse or a human being. Hox genes are found throughout the animal world. As new animals have evolved, their number and roles have changed slightly, but they still perform basically the same function.

There are many ways in which genes can take on new functions. The classical way is through mutation, a change in DNA sequence altering the properties of the protein (or RNA) that it codes for. But mutation does not necessarily change the protein (or RNA); if it affects control regions, the protein may be made in a different place in the body or at a different time during an organism’s life.

Sometimes genes or collections of genes (or even entire genomes) are duplicated. The vertebrate Hox genes, for example, come in four clusters, duplications of a single original group. Following duplication, genes can be free to take on new functions, as one gene can continue to perform its original role.

Loss of gene function does not necessarily mean that the gene disappears from the genome. Genes may become inactivated but remain in the genome as pseudogenes.

The human genome contains a staggering number of pseudogenes – almost as many as there are ‘real’ genes. Remarkably, more than half of our olfactory receptor genes are pseudogenes – evidence of how the sense of smell has become much less important to us.

Lead image:

Cats are indifferent to sweet things because they cannot taste sugar. A gene coding for part of the sugar receptor is a pseudogene.

iStockphoto

References

Questions for discussion

  • Are all pseudogenes ‘non-functional’?

Further reading

About this resource

This resource was first published in ‘Evolution’ in January 2007 and reviewed and updated in December 2014.

Topics:
Cell biology, Genetics and genomics, Biotechnology and engineering
Issue:
Evolution
Education levels:
16–19, Continuing professional development