<span>All mammals have at least one X chromosome. Female mammals have two X chromosomes, so each of her eggs has a single X chromosome. Male mammals have XY chromosomes, meaning they can generate sperm containing the X chromosome, or sperm containing the Y. If the egg receives sperm containing the X chromosome, then the resulting individual forms ovaries, and is female.</span>
PROMOTER is a DNA sequence where RNA polymerase binds and begins the process of transcription. ENHANCER is a D N A sequence that binds regulatory proteins that interact with promoter-bound proteins to activate transcription.
