Re: "Junk worth keeping,"1 just because functions have been identified for some regions of genomes thought to be non-functional does not mean that all regions thought to be junk are functional. This is particularly true for bloated genomes (like the human genome) which are loaded with parasitic elements.
A nearly neutral model for the evolution of eukaryotic genome structure, proposed by Michael Lynch2, suggests that mutational biases can overwhelm the costs associated with many deleterious changes if population sizes are small enough. If so, many features of eukaryotic genomes (introns, elaborate transcriptional regulatory systems, etc.) would be the result of semi-neutral processes, not adaptive evolution.
Richard Meisel
The Pennsylvania State University
University Park, PA
meisel@psu.edu
As an assistant professor constantly thinking about tenure (thus, thinking about funding), I couldn't agree more with Adam Jaffe's assertion in "Double research funding? Be careful" 1 that the current funding situation is bad, frightening, terrifying, ...