The American Heritage® Dictionary of the English Language, 4th edition Copyright © 2010 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
A gene for maleness found on the Y chromosome. It has a key role in development of the testes and determination of sex.
Origin: s(ex-determining) r(egion) Y.