Figure 1.

Dosage compensation in Drosophila equalizes sex chromosome expression between males and females. (A) Drosophila males have one X chromosome while females have two. Males increase transcription from their X-linked genes approximately two-fold to equalize expression. (B) The Male Specific Lethal (MSL) complex, composed of five proteins and a long non-coding RNA, is recruited to CLAMP-bound Chromatin Entry Sites (red) on the X chromosome. The MSL complex then spreads in cis to nearby transcribed genes by recognition of active chromatin marks. (C) Polytene chromosome preparation from a wild type male. MSL2, detected by Texas Red, identifies the X chromosome. DNA is counterstained with DAPI (blue).