Editing Hyperactivation (section)

{{Short description|Type of sperm cell motility}}
{{Refimprove|date=September 2014}}
'''Hyperactivation''' is a type of [[Spermatozoon|sperm]] [[motility]].  Hyperactivated sperm motility is characterised by a high amplitude, asymmetrical beating pattern of the sperm tail ([[flagellum]]).  This type of motility may aid in sperm penetration of the [[zona pellucida]], which encloses the [[ovum]].<ref>{{cite journal |last1=Suarez |first1=SS |title=Hyperactivated motility in sperm. |journal=Reproduction in Domestic Animals |date=21 March 2003 |volume=38 |issue=2 |pages=119–24 |doi=10.1046/j.1439-0531.2003.00397.x |pmid=12654022}}</ref>

Hyperactivation could then be followed by the [[acrosome reaction]] where the cap-like structure on the head of the cell releases the enzymes it contains.  This facilitates the penetration of the ovum and fertilisation.

Some definitions consider '''sperm activation''' to consist of these two processes of '''hyperactivation''' and the '''acrosome reaction'''.

Hyperactivation is a term also used to express an X chromosome gene dosage compensation mechanism and is seen in Drosophila. Here, a complex of proteins bind to the X-linked genes to effectively double their genetic activity. This allows males (XY) to have equal genetic activity as females (XX), whose X's are not hyperactivated.