Readers Nuggets:

Wanted to know more about dodo cloning? PSD takes us through a few of the pitfalls regarding a notoriously tricky branch of science.

The top conclusion is that it'd be a bloody hard thing to achieve. In fact, if I were cloning Dodos - Didus ineptus or Raphus cucculatus (sources vary, possibly due to confusion with the solitaire, which looked like a dodo and went extinct at the same time through spending too much time playing crap card games) - I wouldn't start from here...

I'll explain why it would be impossible below, however.

Go straight to jail, do not collect DNA, do not pass go

One reason that poeple are optimistic about recreating extinct species is becasue DNA has been isolated from preserved remains. THey see that scientists have been able to comapre the DNA to extant species to examine evolutionary relationships, and assume that this means that the genetic information is usable.

The problem is that DNA degrades very quickly after death. For DNA fingerprinting this is not a problem, because of the way fingerprinting works. To create a DNA fingerprint you isolate the DNA of the species in question (you can do this with household chemicals, if you're so inclined), and then use restriction enzymes to cut it into chunks.

Restriction enzymes work by recognising certain sequences in the code and cutting the DNA at that point. HindII, for example, always cuts DNA at the sequence GTTAAC or GTCGAC. Every time the enzyme meets its recognition sequence, it will snip the DNA in two.

Because each genome will contain many sequences that provoke cutting at different lengths apart, each genome will produce different numbers of smaller or larger chunks of DNA. THis DNA is then placed in a gel, and an electric current run across.

This curent moves the DNA molecules through the gel, with smaller lengths of DNA able to move faster. This spreads the DNA segments out into bands - exactly as you see whenever DNA fingerprints are shown on the news.

Because DNA is cut up to enable fingerprinting, the fact that it has already fallen into pieces is no hinderance, as the enzymes merely create still smaller chunks. THis is why it is possible to compare old and contemporary DNA.

However, for cloning, one would need to have an entire genome, in order. The preserved DNA sin't good enough for this.

Firstly, any dodo flesh that has been preserved has been dried. Oxygen can still get to it, and DNA + heat = 1 big chemical mess. Frozen mammoths are likely to have better DNA than a dodo, and it's stilll useless.

It has been argued that if we can get enough chunks we could compare the dodo to other members of the pigeon family. THis is fair enough, it would give us some important markers for working out where genes ought to be. Unfortuantely DNA does some very strange things, and important mutations may not be reconstructable through comparison.

For example, one type of mutation is inversion, where a section turns itself around in the sequence. A part of the genome reading CATCATCAT now reads CATTACCAT, for example. If a large section of a chromosome is reversed in this way in only the dodo you might not notice by comparing it to extant pigeons. Mr Ff's reference to splicing would be great - fill in gaps with DNA from somewhere else - if only we knew where the bleedin' gaps were to be filled.

Community Chest

The other issue is a slightly philosophical one. Is a newly un-extincted dodo a dodo?

It may share a load of DNA with a dodo (although not microsomal DNA, importantly), it may look like a dodo and plock like a dodo. This doesn't make it a dodo.

The dodo appears to have reproduced slowly, and this normally goes hand-in-hand with caring for the young for a time after hatching in order to teach them how to find food, behave, sing etc. This is something that many birds of prey do, for instance.

In the case of a newly cloned dodo, there's no adult bird to copy behaviour off. Our cloned dodo would show none of the behaviours that were learnt through 'culture', if you like. Behaving in this way, would it be a dodo? WE would learn something about dodo physiology, but little about dodos as a species.

Free parking

In short, it's impossible - if not harder - to clone a dodo. I would suggest that it would be better to invest the funds and effort into studying a different species before it went extinct and joined the dodo.

The real interest in the dodo is because it became a metaphor for extinction through human action, rather than any stand out feature of it as a bird. The resources would be better spent tackling avian malaria in the Hawaiian honeycreepers, helping the Kakapo and many other birds that are far more interesting and far more alive than the dodo.

Incidentally, I actually think the extinction of the Passenger Pigeon is far more important as a lesson about how humans can bugger up even the most common species, and part of me suspects the reason the dodo is mentioned more often is because the blame can be laid at the feet of colonial powers rather than the USA. The idea that the dodo was a victim of a fight for sea power (including the myth that they were made extinct for food) is a more powerful story for us than the destruction of the Passenger Pigeon for amusement and pig food.

Ben Tymens, AKA PSD