Читать книгу Human Developmental Biology - Danton Inc. O'Day - Страница 6

The germ plasm is morphologically similar in all lower animals. However a defined cytoplasmic localization of germ plasm material has not been detected in mammals. Germ plasm contains dense fibrillar and granular material. The particles have been shown to contain RNA and protein. Mitochondria and ribosomes are also localized within the germ plasm. This concentration of components segregates into specific cells during cleavage. Those cells that receive the germ plasm during cleavage are destined to become germ-line cells while those that don’t will become somatic cells of the body. Extensive research has been done on Drosophila and other organisms (e.g., Caenorhabditis) which has helped the study of germ-line determination in humans. These germ-line determinants have been found to be genetically controlled. A diversity of experiments has shown that specific mRNAs localized in the germ plasm are the cytoplasmic determinants that direct the formation of germ cells.