O + chromobox 1 Cbx-rs2 genetic mapping Cbx1 Gene M31 http://identifiers.org/mgd/MGI:105369 HP1B E430007M08Rik protein coding gene Hp1beta MGI:105369 Cbx-rs2|E430007M08Rik|M31|Hp1beta|HP1B|MOD1 MOD1