Unqualified Offerings

By Thoreau

In the past 24 hours I’ve read two interesting pieces on evolution and developmental biology:

1)  In the latest Scientific American, there’s a nice article explaining the role of regulatory DNA sequences in shaping anatomy.  An amazing number of genes are quite similar throughout the vertebrate family tree, yet vertebrates come in all shapes and sizes. One reason is sequences of DNA that don’t get translated into proteins but do affect when protein-coding sequences are turned on and off.  These sequences play a crucial role in deciding which cells will exhibit which traits, and they provide a means by which a gene can be used again and again for a variety of purposes.  That wheel doesn’t have to be reinvented; instead, changes in much smaller sequences of DNA are sufficient to give rise to changes during the course of evolution.

2)  In the latest issue of Developmental Dynamics (a research journal) there’s a nice article highlighting the importance of evolutionary theory in this field:

Nowhere is the topic of evolution more interconnected than with the study of developmental biology. Understanding the establishment of pattern and form in a developing embryo necessitates a greater appreciation of the genes that control these processes across species. It has become impossible to describe embryonic development without considering the conserved roles of transcription factors and members of signaling pathways, components of the so-called genetic toolkit, that are used reiteratively and in different contexts.

The DNA sequences that don’t code for proteins are hard to analyze because they don’t include the “start” and “stop” sequences that mark gene sequences.  This DNA has historically been referred to as “junk DNA” but as we’re learning more we realize that “junk” is a misnomer.  However, difficulties in interpretation can slow the work.  Evolutionary insights regarding conserved sequences in related species can be helpful in analyzing the “junk” DNA.  If you can’t find a marker saying “This codes for a protein!” you can at least observe that a bunch of related species all contain the same sequence that doesn’t code for a protein, and from there you can get ideas that lead to testable hypotheses.

No, the role of conserved non-coding sequences doesn’t lead to predictions quite as hard and quantifiable as those in certain areas of physics, and yes, you could probably do this work without thinking about evolution, if you put yourself through some mental gymnastics.  However, it’s damn hard to do this without some concept of species sharing common lineages leading to similar conserved sequences, with the degree of variation increasing as the common ancestors become more ancient.