Texas Tech University

Lewis Irving Held

Associate Professor
Developmental Genetics

Email: See TTU Directory

Phone: (806) 834-3283

  • Ph.D., Molecular Biology, University of California Berkeley, 1977.
  • B.S., Life Sciences, Massachusetts Institute of  Technology, 1973.

Teaching Awards

Book Awards

  • 2nd Place Medal, TTU University-wide Book Competition, 2004.
  • 2nd Place Medal, TTU University-wide Book Competition, 2011.
  • 3rd Place Medal, TTU University-wide Book Competition, 2016.
Dr. Held

Web Links:


Wall Street Journal
interviews Prof. Held about Darwinian evolution

Cambridge Univ. Press interviews Prof. Held about Darwin's legacy

Daily Toreador interviews Prof. Held about life & a fly joint mutation


For student use only (BIOL 3302):  CRISPR as a DNA-editing tool; StemCells1; StemCells2; StemCells&Cancer; Organoids1Organoids2; Organoids3; Organoids can repair the retina!;RegrowArms?; MorphogenGradients; Morphogen Case Study: Axes of the Inner Ear; Source-SinkGradients; HedgehogPathway; MovieTranscript.

Click here to access the 6th Edition of Gilbert's textbook Developmental Biology.
Click here to search for other (free) digital copies of science textbooks.

For student use only (BIOL 4110):  EvoDevoVideo1; EvoDevoVideo2; EvoDevoSlideshow; EvoDevo1EvoDevo2EvoDevo3EvoDevo4; FlyArt.

For student use only (BIOL 1403):  EvolutionSlideshow.

"Playgrounds" for Pre-medical Student Explorers

NCBI:   The National Center for Biotechnology Information
PubMed:  Database of (clinically-related) published articles
OMIM:  Database of genetically caused diseases in humans


Flies ≈ humans!
OrganSystems; Vision; WhyFlies?Video1(Basic); WhyFlies?Video2(Advanced); WhyFlies1?WhyFlies2?WhyFlies3?WhyFlies4?; WhyFlies5?; WhyFlies6?; WhyFlies7?; WhyFlies8?; WhyFlies9?; WhyFlies10?; WhyFlies11?; WhyFlies12?; WhyFlies13?; WhyFlies14?; FlyWorld1; Links-to-Literature.

"Wonderlands" of Fly Genes InteractiveFly; FunWithFlies; Twitter; Nobel Prizes.

Nobel Prize to 3 Fly Guys (2017): Awarded for basic research on circadian rhythms in fruit flies to Jeff Hall, Michael Rosbash, and Michael Young.

Whimsical musical parodiesEvo-devo (lyrics); Biochemistry; Science appreciation; catalog of Tim Blais videos.

Seminar "Hamlet on the Fly": Slide presentation; Slide comments.

Research Interests

Research in my lab has focused on pattern formation: how do cells construct anatomy? The model system we have used is the leg of the fruit fly and its exquisitely intricate patterns of bristles. Over the years we have probed how various signaling pathways (TGF-beta, Wnt, and EGFR) establish the axes, boundaries, and coordinates of the leg landscape.  Recently we solved (at least partially) an intriguing riddle in evolutionary developmental (evo-devo) biology: how did the 1st pair of legs become different from the 2nd pair in terms of its sex comb (on the male tarsus) and its transverse rows (on the tibiae of both sexes)?  We found that a master gene in the Hox complex (called Scr ) causes transverse row bristles to be yellow and bractless by direct intervention, whereas its other effects appear to be mediated indirectly by as-yet unidentified circuits.  Currently we are using RNAi to probe the role of cell movements (as controlled by Rac & Rho) in fine-tuning bristle alignments, which are astoundingly regular in transverse rows & elsewhere.

Selected Publications

Department of Biological Sciences

  • Address

    Department of Biological Sciences, Texas Tech University, Box 43131 Lubbock, TX 79409
  • Phone

  • Email