2

FIGURĘ 20.14 Novel Gene Derived from Pre-Existing Modules

(A) Modular evolution of a new gene mciy involve the fusion of separate gene modules, or funcłional units. For example, the orange module of gene 1 may provide a function that complements the purple module of gene 2. If these two domains fuse they might then form a novel but functional gene. (B) The LDL receptor has domains found in several other proteins. The first part of the LDL receptor gene has seven repeated modules or functional units also found in the C9 complement factor of the immune system. The next module allows the protein to bind the celi membranę. This module is very similar to a portion of the epidermal growth factor receptor. Finally, the LDL receptor has a module that is unigue.

A. Principlf. of modular eyolution

Gcnc 1

Gcnc 2

RECOMBINAITON    New gcnc

B. 1.1)1. RECEPTOR - AN EXAMPI£ OE MODU1AR EYOLUTION

Protein

modules

New protein

(LDL

receptor)

Complement CO protein

F.pidcrmal growth factor

Binds LDL    Sticks into Unique to

membranę LDL receptor