His main research focuses primarily on the issue of genome size evolution (the "C-value enigma") in animals and the origins and biological significance of "junk DNA".
He outlined the Onion Test as a "reality check for anyone who thinks they have come up with a universal function for junk DNA".
Gregory is the author of more than 65 peer-reviewed scientific journal articles with an h-index of 51 according to Google Scholar,[3][4] and edited the book The Evolution of the Genome in 2004.
He is Senior Handling Editor of the journal Evolution: Education and Outreach founded by Niles Eldredge.
[5] He maintained a blog, Genomicron,[6] and created Evolver Zone,[7] an online resource for students and educators.