This New Year as the weather turns chilly, spare a thought
for the orphan genes. Around a third of all genes in all genomes have no
relatives – no parents, no family tree, no evolutionary past. They’ve had a
tough time of it and they’re struggling for recognition.
Orphan genes are genes found in just one species (or a group
of closely related species) and nowhere else – the jellyfish gene that guides
the formation of stinging cells, the polar cod gene that prevents the fish from
freezing, and the fruit fly gene that helps it to fly. They may even have
stimulated the evolution of human brain. They’re innovative and they’re
everywhere – orphan genes have been found in all of the genomes examined so far.
But because they have no obvious relatives, they struggle to
fit into evolutionary theory. Genes, like all life, must have evolved from
somewhere. Most genes are formed from other genes, creating a traceable family
history. So how are orphan genes made?
Creationists have cited the apparent incompatibility between
orphan genes and evolutionary theory as evidence of intelligent design. It’s not. They’re actually an example of natural selection at its finest.
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| Photo by John Goode DNA at the Science Museum |
The majority of orphan genes, it now seems, lack obvious
parents because they’ve sprung up from junk DNA. The idea, once considered
totally implausible, is gathering credence as scientific papers pinpoint the
non-coding sequences and processes that have forged these foundlings.
Our cells may be constantly experimenting with
new genes all the time – ‘testing’ random stretches of non-coding DNA to see if
they can produce anything useful. The cell’s cytoplasm is bustling with
well-coordinated activity, so most of the proteins manufactured from these
sequences won’t fit in. The wannabe gene won’t be selected for, and reverts to
plain old, non-coding DNA. But once in a while, junk DNA throws up something
useful. The sequence may then start to pick up useful mutations, and over
millions of years of natural selection it becomes shaped it into a fully
functional gene.
So spare a thought for the orphan gene. Its parents might
not look like much – just a jumble of DNA letters arranged in a long string.
But orphan genes are masters of innovation. And their success today, means are likely
to go on and have families of their own. A happy ending for the orphan gene.
Would you like to find out more?
Have a look at the article I wrote for New Scientist:
Genes from nowhere - Orphans with a surprising story
Also:
Genes from nowhere - Orphans with a surprising story
Also:
