Hopeful monsters

Last week, I posted about homeotic mutant flyheads with their antennae transformed into legs, also known as hopeful monsters.

I was wondering why they are called hopeful monsters. Monsters are supposed to be scary and powerful, like the cartoon below. Why do they need hope for?

Turns out that in reality such grossly mutated monsters don't have the phenotype that is favorable for survival or reproductive propagation. Imagine the fly with legs on its head walking upside down. It isn't going to go very far.

I'm digressing. Anyway to start understanding how this occur, let's observe the photographs closely.

Note how "clean" the transformation from antenna to leg is.

The transformation of one structure of the body did not affect the adjacent structures.

So what does this suggest?

That one structure develops independently of the other neighbouring structures.

Uh huh...but how did mutation cause the leg to end up on the head?

Have you heard of Hox genes? These are really cool genes that determine where limbs and other body segments will grow in a developing embryo.

So in the drosophila embryo, each region is specified by a cluster of Hox genes (below). So does it make sense that one part of the fly develops independently of the other parts?

Here's another blog that explains Hox genes in greater depths.

When you mutate one of the genes, mess up with one of the switches and viola! As if a magical trick, the leg ends up there.

Um, magic is not a very good explanation but I am sleepy. Stay tuned to the next blog post for explanation on switches..