Tag Archives: development

The difference between homeobox and Hox genes

This is a big pet peeve. Let’s get straight to business: the terms “homeobox” and “Hox” are not interchangeable. They do mean different things. I’m correct in saying that Amphioxus (Branchiostoma lanceolatum) has 15 Hox genes. I’m also correct in pointing out that it has over 130 homeobox genes.

Gene names can be very confusing and difficult to remember, so there are many abbreviations in biology. For example, the gene insulin-like growth factor 1 is abbreviated to Igf1. Does that make it easier to remember? Who knows. But I believe the use of abbreviations is partly responsible for the incredible confusion over homeobox and Hox genes. And I do mean incredible. It’s very obviously a confusing topic for students, or anyone new to evo-devo, developmental genetics, or gene regulation… but it’s so much worse than that. Professional publications make the mistake, academics make the mistake, and they do it often. I think the reason it keeps happening is that the word “Hox” appears to be a shortened “Homeobox”. All over the internet you will see the terms used interchangeably, and sometimes with the apparently shortened version in brackets. “Homeobox (Hox)”. This otherwise decent glossary for Epigenesys manages to dump the terms homeotic, homeobox, and Hox into one single paragraph and glossary entry, which is of little help to a confused student seeking clarity. So let’s clear this up, and I’ll keep it quick.  Continue reading The difference between homeobox and Hox genes

The Monday Quote #4

A T.H. double-whammy this week for embryology and development. First, a 19th century appreciation for the wonder that is biological development. Also, a comment on how mere wonder isn’t enough if we wish to truly understand development, and that experimental embryology must supplant purely descriptive embryology.


“The student of Nature wonders the more and is astonished the less, the more conversant he becomes with her operations; but of all the perennial miracles she offers to his inspection, perhaps the most worthy of admiration is the development of a plant or animal from its embryo.”

– T.H. Huxley, Darwiniana, 1896, p.29.


“A transparent egg as it develops is one of the most fascinating objects in the world of living beings. The continuous change in form that takes place from hour to hour puzzles us by its very simplicity. The geometric patterns that present themselves at every turn invite mathematical analysis. The constancy and oderliness of the whole series of events, repeating themselves a thousandfold in every batch of eggs, assures us of a causal sequence conspiring to create an object whose parts are adjusted to make a machine of extraordinary complexity.

This pageant makes an irresistible appeal to the emotional and artistic sides of our nature. Hence not without a feeling of jealous regret, the old-fashioned embryologist sees these gems of nature consigned to test tubes for chemical analysis, to centrifuges to disturb their arrangements, to microdissecting instruments to pick them to pieces, and to endless tortures by alternations in the environment to disturb the orderly, normal course of events. Yet we feel, too, that if the mystery that surrounds embryology is ever to come within our comprehension, we must try not to be sentimental and have recourse to other means than description of the passing show. The recompense, we hope, will be to substitute a more intelligent interest in place of the older emotional response to the order of nature.”

– T.H. Morgan, Experimental Embryology, 1927



Of course, there’s nothing wrong with having an emotional response to nature. Morgan’s point was that we wouldn’t begin to understand the mystery that was development unless the field took an experimental approach.

EmbryologyExperimentalQuotesTH HuxleyTH MorganThe Monday Quote

The Monday Quote #1

I occasionally find obscure and often brilliant quotes and add them to a little collection. Because I come across some in weird places, they usually aren’t quotes I see regularly posted anywhere else, so I thought I’d start sharing them here. This one combines many of my interests including evolution, developmental biology, creationism, and a healthy dose of 19th century wit and sarcasm.

20121231-150908.jpg

“What say the schools to this case? Whence and for what purpose, if the Serpulae were produced or created as ready-formed species, these lateral filaments of the opercular peduncle? To allow them to sprout forth merely for the sake of an invariable plan of structure, even when they must be immediately retracted again as superfluous, would certainly be an evidence rather of childish trifling or dictatorial pedantry, than of infinite wisdom. But no, I am mistaken; from the beginning of all things the Creator knew, that one day the inquisitive children of men would grope about after analogies and homologies, and that Christian naturalists would busy themselves with thinking out his Creative ideas; at any rate, in order to facilitate the discernment by the former that the opercular peduncle of the Serpulae is homologous with a branchial filament, He allowed it to make a détour in its development, and pass through the form of a barbate branchial filament.”

– Fritz Müller, Facts and Arguments for Darwin (English translation of Für Darwin), 1869, p.114.