...a blog by Richard Flowers

Thursday, December 21, 2006

Day 2177: Virgin Birth: It's a Lizard!


Flora the Komodo Dragon Lizard, the biggest lizard in the world, who has never KNOWN a boy lizard, has given birth to a clutch of eggs and is looking forward to babies by Christmas.


Apparently it is down to CHROMOSOMES! If you think of your DNA as the blueprints for building you, then your chromosomes are sort of the volumes of the encyclopaedia that your DNA is put in.

It's not REALLY like a blueprint, though: DNA is more sort of like a little set of workers who come in and do one job each. If you have all the right workers in all the right order then you get a bathroom at the end!

So, chromosomes are like the flats where your little workers live.

Among your "blocks of flats", you human beings have a pair called sex chromosomes: they are called "X" and "Y". This does NOT mean these are the married quarters! If you have two of chromosome "X" then you are a lady human being and if you have one "X" and one "Y" then you are a boy human being. Basically lady human beings get a whole load of extra DNA workers who enable them to do extra things like give birth, cook an entire Christmas dinner or understand what Barbara Cartland is all about.

Lizards on the other fluffy foot have it the other way around. Because Flora is a lady lizard she has two DIFFERENT sex chromosomes, called "W" and "Z". If she had two "W" chromosomes then she would be a boy!

Flora's babies will not be EXACT clones of their mummy, because rather than having the same DNA, they will have one half-copy of her DNA which then doubles itself up to make a full set of DNA. When you look at what you get, one half of the times you will get double "Z" which does not work, and the other half of times you will get double "W" which becomes a new baby boy lizard.

In fact, this means that ALL baby lizards born this way are always boy lizards.

(I will gloss over what happens next… just think Oedipus Rex. Ew!)

But this means that an isolated lady lizard can restart the population. This is a helpful EVOLUTIONARY trick, which allows your species to send out lone female colonists – swimming to new islands say – and spread out.

Obviously, because your chromosomes are different, if human people could do this, then a lady human would always give birth to GIRLS, because she does not have any of the "Y" chromosomes needed to turn a sugar'n'spice little girl who likes ponies into a slugs'n'snails little boy who likes cars.

Now, some of you MIGHT be thinking that this a handy way of doing away with boys altogether – and scientists in JAPAN seem to have found a way to make it happen! If you are a MOUSE!

That, however, is an entirely artificial process (there would be some IRONY in calling a baby from all lady reproduction "man-made") and does not really work very well. At least not at the moment: I am sure some scientist will be working on it!

[R: paging Dr Frankenstein, paging Dr Frankenstein]

Nature, over millions of years of evolution, has gotten there first with a branch on the tree of life of all-lady species: a group of tiny shrimp called – isn't THIS cool – Darwinulids who have been managing without boys since before the Dinosaurs roamed the Earth! (Or have they…?)

Meanwhile, water fleas aside, parthenogenesis is a rare (if not QUITE miraculously unique) phenomenon that has been observed in several species of VERTEBRATE, including amphibians, lizards and even (maybe) in sharks.

And apparently in turkeys too.

Merry Christmas!

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