chr2 · 2q31.1 · 220 nt · 2006

HAR3

What it is

Hox genes decide where arms, legs, and segments go. They are almost sacred in evolution — the proteins barely change. HAR3 sits in their regulatory desert, where small enhancer edits can shift digit or limb patterning.

Why it matters

Body-plan locus; cis-only acceleration.

Operator load

• 01 · ΔE

  Enhancer activity

  These stretches of DNA do not code for proteins. They act as volume knobs — turning nearby brain-development genes up or down at the right moment.

• 03 · T

  Three-dimensional rewiring

  The genome folds in 3D. Human-specific changes can re-route which switches sit next to which genes, even if the letters look similar in a straight line.

Pollard et al. 2006