Centromere vs Kinetochore
Inheritance of genetic information depends on the proper segregation of chromosome in the process of mitosis and meiosis. Mitosis is the production of genetically identical daughter cells, while Meiosis is the production of daughter cells, which contain one pair of each chromosome that was present in the parental cell. This chromosome segregation is an extremely accurate process. Its microstructure and shape are very important for the segregation process. The process totally depends on the integrity of microtubules. The sites of attachment of microtubules, therefore, should have certain specific properties. Centromere and kinetochore regions in chromosomes play a major role during the cell division.
A centromere is a highly constricted region on a chromosome to which the spindle attaches during the process of mitosis and meiosis. These special regions contain non-histone proteins that protect them from endonuclease digestion and it is free of nucleosomes and de-condensed. The major role of the centromere is to provide sites for kinetochores.
In eukaryotes, the sizes of the centromeres vary, but all have the same function. Most eukaryotes have monocentric centromeres, where the centromere-kinetochore complex is formed at a single point on the chromosome, but there are exceptions (e.g. Some nematodes). Unlike in unicellular organisms, centromeres of multicellular organisms are embedded within constructive centric heterochromatin. Centromeres are composed of highly specialized, repetitive DNA sequences, and it only binds a unique set of proteins. These regions, therefore, chemically differ from the rest of the chromosome.
Kinetochores are the protein complexes associated with the centromeric regions of mitotic and meiotic chromosomes. The functions of these complexes are to bind microtubules of the spindle bundle and depolarize them during the cell division. Many animal cells contain disc-like kinetochores with three distinct layers that are formed on one side of each chromatid. Inner layer is tightly associated with the centromere while the outer layer interacts with microtubules. The function of the middle layer is unknown. Amount of the bound microtubules number varies with the species. For example, Human kinetochore binds approximately 15 microtubles whereas kinetochores from Saccharomyces bind only one microtubule.
In certain organisms like protozoa, some fungi and insects, no kinetochores can be seen as the proteins disintegrate during preparation. Unattached kinetochores have extending-fibres that contain many proteins known as corona. These coronas help to capture microtubules during the cell division. The microtubules associated with kinetochores have long lives, while those in the rest of the spindle have very short lives.
Centromere vs Kinetochore
• Kinetochore is a protein complex. Centromere is a constricted region found on a chromosome with highly specialized, repetitive DNA sequences.
• Kinetochores assembles on the centromere.
• Centromeres are clearly visible with a light microscope as a constricted region on the condensed chromosome while kinetochrores can only be seen with the aid of an electric microscope.
• Unlike in the centromeres, three different layers can be found in the kinetochore.
• Kinetochore has corona while no such structures are found in centromeres.
• Centromeres cannot bind the microtubules. Only the kinetochores that are associated with centromeres have the ability to bind microtubules.