One of the more fascinating mistakes of gene expression: in fruit flies (Drosophila melanogaster), the gene that tells the antenna to form occasionally causes legs to form instead. The top picture is a comparison of a normal (wild type) fruit fly with one with the abnormality (mutants, with this specific abnormality referred to as antennapedia). It turns out, as shown in the second picture, antenna and legs are quite similar (much in the same way that molars and incisors are similar, for example) and occasionally, when genes aren’t expressed properly… this will happen. Definitely makes you stop for a second to appreciate the fact that your genes, for the most part, were expressed correctly.
Zoology fan extraordinaire. I know the blog is called Animalia Chordata, and with that name you might assume this blog only contains chordates, but you should know I'm a huge liar and any animal, topic, or weird gelatinous thing that catches my interest will show up on this blog, notochord or not. If you have any questions or requests, just shoot me a message and I'll see what I can do!