Initiation of Development - Development Biology

We know that the various events collectively called the activation programme. These events are directly related to the formation of the embryo. You have further learnt that the early response to the activation programme is the prevention of polyspermy. The late responses include many metabolic changes such as the activation of potassium ions and amino acid transport, an increase in the rate of the protein synthesis, initiation of DNA replication and several major regulatory events.

These events include production of inositol triphosphate, diacyl glycerol, release of cytoplasmic free calcium ions and rise in hydrogen ion concentration. Figure summarizes the various events that occur during the activation programme of the egg. The egg which has been under a metabolic arrest before fertilization is released from this arrest on the entry of sperm. This initiates the long process of development into a new individual by active protein and DNA synthesis in the egg leading to the beginning of cleavage.