What Is a Centromere?

The centromere refers to the junction of two sister chromatids of the metaphase chromosome, which are located at the main scar of the chromosome. The centromere divides the two chromatids into short arms (p) and long arms (q). A highly repetitive heterochromatin composition whose main components are DNA and protein. Centromeres and telomeres are two special structures that exist in the main ridge. At the junction of the two sister chromatids of the metaphase chromosome, there is an inwardly sunken, lightly colored constriction called the primary constriction. ^[1]

Centromere

Centromeres are specialized DNA sequences that connect a pair of sister chromatids. During mitosis, the spindle filaments are attached to the centromeres through a kinetic particle. Centromeres are primarily considered as loci that direct chromosomal behavior.

Physically, centromeres provide sites for telomere assembly. A telomere is a highly complex protein structure that is actually responsible for chromosome segregation. After all the chromosomes have been combined with the spindle in a suitable way, they bind to tubulin and send signals to the cells to ensure the correct division of the cells.

In a broad sense, centromeres in living things can be divided into two types. "Point centromere" binds to a specific protein and efficiently recognizes DNA sequences. ^[2]

Centromere

The centromere region is generally in a heterochromatin state, which is important for its recruitment of laminin complexes. In this chromatin, the general histone H3 is replaced by another centromeric specific protein (CENP-A in humans). ^[4]

Because centromere DNA sequences are not a key determinant of centromeres in animals, epigenetics are thought to play a key role in the specialization of centromeres. The daughter chromosome formed by chromosome division will form centromere at the same position as the chromosome that formed it, regardless of sequence. It is currently assumed that the H3 histone variant CENP-A is the major epigenetic marker of centromeres. ^[6]

The centromere is actually a telomere often referred to in molecular biology, which is different from the centromere. The centromere is a protein complex, and the telomere (centromere) is a protein complex covering the outside of the centromere. It is mainly responsible for the separation of chromatids during the cell division.

Centromere is the name of the basic chromosome structure commonly used in high school biology textbooks. This textbook uses "centromere" in both mitosis and meiosis-related cell division in Book 1, but uses "centromere" in chromosome classification in Book 2 for karyotyping. Many students question "What is the difference between centromere and centromere? Is it the same structure?"

It was found that the centromere was Kinetochore and the centromere was Centromere, which has been used in many literatures. For example, both are used in Cell Biology (1987, Higher Education Press), while only the "centromere" is used in Liu Zudong and Jiang Shaohui's "Genetics" (1987, Higher Education Press). In the textbook "Plant and Plant Physiology" (revised by Meng Fanjing et al., 1989, Agricultural Press) of the Central Agricultural Radio and Television School, only the "centre point" is used. Recent observations under electron microscopy show that the centromere (primary constriction of chromosomes) is a chromatin structure that divides the chromosome into two arms, and connects two sister chromatids in the early and middle stages of cell division Together, the centromeres of the two chromatids are separated by later stages. On the two sides of the centromere, there is a three-layer disc-shaped specialized structure made of protein, which is an addition to non-chromosomal substances, called the centromere. When chromatin (chromosome) is stained with basic dye, the centromere is The spot is stained lightly or not at all. Since the centromere is almost covered by the centromere, the shape of the chromosome is observed after staining, and the coloration is hardly visible at the centromere. The centromere is related to the movement of chromosomes. Before, during, and after cell division (including mitosis and meiosis), the spindle's spindle (or star-ray) microtubules attach to the centromere and pull the chromosome. Movement means that the spindle filament (or starburst) of the spindle is directly attached to the centromere instead of the chromosome centromere. Without the centromere, the chromosome cannot be moved by the spindle. Therefore, the centromere and centromere are not the same structure, and their functions are also different, but their positional relationship is fixed. Sometimes it is understandable to use the centromere or centromere to refer to the position of the main scar of the chromosome where they are located. of.

According to the seven-year clinical medicine textbook "Cell Biology" published by the People's Medical Publishing House, there is an inwardly dented scar called the primary constriction at the junction of the two sister chromatids. The light microscope The bottom is relatively uncolored. The centromere is located inside the main scar and is the chromatin site of the main scar. Under the electron microscope, a three-layered specialized site on both sides of the main condyle can be seen, called the kinetochore, which is the centromere. Centromeres are currently considered to be a highly repetitive DNA sequence in a chromatid that does not bind to histones. The telomere is a disc-shaped structure formed by the centromere-binding protein at the centromere of the mitotic chromosome. Microtubules are connected to it and are closely related to chromosome separation. There are two telomeres in each metachromosome, located in the centromere. Grain on both sides.

The telomere, also known as the centromere, is a cell structure attached to the centromere. The motile can be divided into 4 parts: inner plate, middle gap, outer plate and fiber crown. During cell division, the microtubules are connected to the kinetochore, and the chromosomes are drawn in the middle stage of chromosome formation. In the late stage of division, the separated chromosomes are drawn toward the poles of the cell.

Centromere-binding proteins and other factors are currently being studied. A major issue is the specific mechanism by which spindle filaments attach to centromeres.