Large changes in quantitative traits can occur by the evolution of allele frequencies without the addition of new mutations.

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#Id: 7573

#Unit 5. Developmental Biology

Sperm rheotaxis 

migrate against the direction of the flow—using

CatSper calcium channels (like sea urchin sperm) to sense calcium influx and monitor the direction of the

current

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#Unit 5. Developmental Biology

The cells of the oviduct induce the sperm to mature, and mammalian sperm complete their development in the female oviducts. This maturation is called capacitation (the gaining of capacity).

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#Id: 7575

#Unit 5. Developmental Biology

The capacities the sperm gain are those for:

recognizing the cues that will guide them to the egg

undergoing the acrosome reaction

fusing with the egg cell membrane

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#Unit 5. Developmental Biology

Sperm that are not capacitated are “held up” in the cumulus matrix and are unable to reach the egg

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#Id: 7577

#Unit 5. Developmental Biology

Capacitation is a transient event, and sperm are given a relatively brief window of competence during which they can successfully fertilize the egg. As the sperm reach the ampulla, they acquire competence—but they lose it if they stay around too long

TLS Online TPP Program

#Id: 7578

#Unit 5. Developmental Biology

The molecular processes of capacitation prepare the sperm for the acrosome reaction and enable the sperm to become hyperactive