AP BIOLOGY

Detailed explanation-1: -But every cell differentiated into a certain type of cell because specific genes are activated in specific types of cells which allow these cells to be formed and differentiated. Hence, a fertilized egg divides into certain cells because the specific genes for each type of cell become activated.

Detailed explanation-2: -In order for cells to become whole organisms, they must divide and differentiate. Cells divide all the time. That means that just one cell, a fertilized egg, is able to become the trillions of cells that make up your body, just by dividing. Those trillions of cells are not all the same though.

Detailed explanation-3: -Cell differentiation is caused by changes in gene expression. This occurs when different signaling molecules in the environment activate or repress different transcription factors that are necessary to express certain genes in the DNA.

Detailed explanation-4: -In sexually reproducing organisms, fertilization of an ovum with a sperm induces not only cleavage (cellular multiplication) of the zygote, but also cell determination (deciding the fate of the cells) and cell differentiation so as to generate cells that do different jobs.

Detailed explanation-5: -A developing egg is called an oocyte. Its differentiation into a mature egg (or ovum) involves a series of changes whose timing is geared to the steps of meiosis in which the germ cells go through their two final, highly specialized divisions.