Cell Biology Origins

the tissue the cells make together, and finally, the organs and phenotype of the human, plant, or animal that is visible to the outside world.

Molecular biology, then, refers to the study of cellular replication, cell function, transcription of genes, and translation of genetic material into proteins, enzymes, and other molecules. The central focus of molecular biology is how DNA creates transcription RNA that goes on in the cell to make the important proteins necessary for cell function. One subfield of molecular biology is molecular genetics, which studies the DNA molecule, how DNA and RNA work together, and how genetic diseases can be defined as mutations in the genetic code of the various cells of the body.

As mentioned, all of cell biology starts with the fusion of the sperm and egg in the fertilization process. When this happens, the result is a zygote, which is an alternate term for the fertilized egg. As this cell divides, it forms a cluster of cells that are all similar in nature, called a blastula. The divisions of this original cell happen quite quickly with no cellular growth so that the daughter cells are smaller in size than the original cell and the embryo does not increase in size. This type of cell division is referred to as cleavage divisions.

Figure 1 shows the different germ layers:

Figure 1