Question

Zona pellucida disintegrates just

• A. Before fertilization
• B. After fertilization
• C. Midway during cleavage
• D. After completion of cleavage

Answer 1

The correct option is D After completion of cleavage

At the fertilisation site, the enzymes present in the acrosome of the sperm help in the entry of the sperm into the ovum. The hyaluronidase enzyme helps to dissolve hyaluronic acid polymers in the intercellular spaces which hold granulosa cells of corona radiata together; corona penetrating enzyme ( that dissolves the corona radiata) and acrosin (which dissolves the zona pellucida). The zona pellucida starts dissolving, however, it disintegrates completely only after the formation of blastocyst and completion of cleavage. So the correct answer is D.