Syncytial specification occurs when cell fates are determined in a syncytium of nuclei, as in the

Drosophila blastoderm

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#Id: 7598

#Unit 5. Developmental Biology

The mouse zona pellucida is made of three major glycoproteins—ZP1, ZP2, and ZP3

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#Id: 7599

#Unit 5. Developmental Biology

The human zona pellucida has four major glycoproteins— ZP1, ZP2, ZP3, and ZP4

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#Id: 7600

#Unit 5. Developmental Biology

The mammalian egg encounters a heterogeneous population of sperm. Some sperm have undergone the acrosome reaction in or near the cumulus, whereas others have not. The egg have pathways for accepting both types of capacitated sperm.

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#Unit 5. Developmental Biology

In one pathway, sperm that have undergone the acrosome reaction bind directly to ZP2

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#Id: 7602

#Unit 5. Developmental Biology

In 2nd pathway, sperm with intact acrosomes become bound to ZP3, which causes the acrosome reaction, and the sperm binding is then transferred to ZP2

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#Id: 7603

#Unit 5. Developmental Biology

Two important acrosomal proteins  acrosin and MMP2 (matrix metaloproteinase-2)