Normal fertilization requires changes in the membrane organization of both sperm

Question

Normal fertilization requires changes in the membrane organization of both sperm and oocyte and penetration of the oocyte by a single spermatozoon.

a. What physical, cellular and biochemical molecular processes are necessary for the succesful passage of a spem from the outermost portion of the cumulus oophorus to the oocyte membrane?

b. How does the human sperm nucleus move in the cytoplasm and why does it facilitate the juxtaposition of the material and paternal pronuclei?

c. why is the orientation of pronuclear DNA critical for embryogenesis to proceed and how does it promote pronuclear membrane breakdown (syngamy)

d. What specific defects in the above processes have been shown to result in fertilization or early developmental failure?

Explanation / Answer

Due to chemoattaction, sperm reaches follicular cells and then binds to zona pellucidaof ovum. Hydrolytic enzymes in acrosome of sperm are released by process of exocytosis and thus sperm undergo capacitation and acrosomal reaction to penetrate zona pellucida of ovum. Then hyaluronidase enzymes then neutralises Hyaluronic acid of cumulus oophorus cells and penetrate it.

Once sperm fuses egg plasma membrane, it releases its nuclei and other cell organelle into egg cytoplasm. After fertilisation, sperm and ovum pronuclei, ( haploid nuclei) juxtapose and carry out DNA replication. Membrane of each pro-nuclei breaks down and first mitotic division of fertilised egg takes place.

sperm looses it effectivity in binding to ovum plasma membrane when sperms are fertilin deficient.

Multiple sperm fertilisation to an egg leads to abnormal fertilisation due to 3 or more pronuclei instead of normal 2 pronuclei.

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