Nuclear envelope

The nuclear envelope (nucleolemma) consists of an outer nuclear membrane (m. Nuclearis externa) and the inner envelope membrane (m. Nuclearis interna), separated by a perinuclear space or tank of the nuclear envelope (cisterna nucleolemmae). The nuclear envelope contains the nuclear pores (pori nucleares).

The membranes of the nuclear envelope is not morphologically different from other intracellular membranes. In general terms, the nuclear envelope may be provided as a hollow double-layer bag, separating the contents of the nucleus from the cytoplasm.

The outer membrane of the nuclear envelope, directly in contact with the cytoplasm of the cell, has a number of structural features that allow it to carry proper membrane system of the endoplasmic reticulum: it from hyaloplasm are numerous ribosomes, and the very outer nuclear membrane may go directly to the membrane of the endoplasmic reticulum. The inner membrane is associated with chromosomal material of the nucleus.

The number depends on the nuclear pore complex metabolic activity of the cells: the more intensively synthetic processes in the cells, the more pores per unit surface area of the cell nucleus. So, erythroblasts (progenitors of nucleated red) lower vertebrates during intensive synthesis and accumulation of hemoglobin found in the nuclear core 30 about 1 micron pores at 2. After these processes end up in the nuclei of mature cells - red blood cells cease DNA synthesis and RNA and the number of pores is reduced by 1 to 5 mm2. In nuclear shells fully mature sperm pores can not be detected.

Some terms:

chromosomal diseases - diseases that occur due to changes in the number or structure of chromosomes in violation of gametes or in the early stages of crushing zygote;

mutation (s) (lat. mutatio change, change) - a universal property of living organisms that underlies the evolution and selection of all life forms and concludes in a sudden change of genetic information;

mutational balance - a balance between the frequency of occurrence and the elimination rate of mutations in the population;

female sex chromatin (syn .: Barr body, X-chromatin) - tightly paintable large part of the chromosome triangular, round or rod-shaped, located on the periphery of the nucleus of a somatic cell of the female body; is a fused X-chromosome; male sex chromatin (syn. Y-chromatin) - large clumps chromosomes in the nucleus of a somatic cell of the male body, glowing with color fluorochrome - derivatives of acridine orange, for example. quinacrine; is a fused portion of the long arm of Y-chromosome;

Test questions:

1. The functions of the cell nucleus

2. Chemical composition of the nucleus

3. Organization nukleolemmy

4. The organization of chromatin

5. The structure and role of the nucleolus and nucleoplasm