Chromosome is the structure formed
by the condensation of chromatin during cell division. It consists of long DNA
strand wrapped around histone proteins. Each chromosome has a primary constriction
point called the centromere, which divides the chromosome into two sections, or
“arms.” The short arm of is labeled the “p arm” and the long arm of the
chromosome is called the “q arm.”
Electron
microscopic studies of the centromeric region revealed the presence of a
protein complex around the centromere called kinetochore. Kinetochore is the
protein complex associated with the centromeric regions of mitotic and meiotic chromosomes.
Microtubules attached to the kinetochore during cell division.
Centromere vs Kinetochore
Centromere
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Kinetochore
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It is the primary constriction of the
condensed chromosome.
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Kinetochores are disc shaped protein
complexes intimately associated with centromere.
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Centromeres are
clearly visible with a light microscope as a constricted region on the
condensed chromosome
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Kinetochrores can
only be seen using electron microscope
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It is the site of kinetochore assembly
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It is the site of
assembly and disassembly of microtubules
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It is made up of
highly repetitive, condensed AT rich, heterochromatic DNA with
non-histone proteins
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Made up of multiple proteins. It has a
trilaminar structure. The inner layer is in close contact with condensed
centromeric heterochromatin. Microtubules are attached to the outer layer.
The middle layer is less dense.
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Fibrous corona like structure is absent. It
is made up of highly condensed repetitive DNA with some proteins
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Fibrous Corona: In the absence of
microtubules, a meshwork of fibers, termed the fibrous corona, can be
seen to extend from the surface of the outer plate. . The fibrous corona and
the outer plate contain the majority of the known Microtubule-interacting
proteins (CENP-E, dynein etc) as well as checkpoint proteins (Bub1, Mad2 etc)
that monitor the integrity of kinetochore attachments.
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Functions of Centromere:
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Functions of Kinetochore:
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References:
- Appels, R., Morris, R., Gill, B. S., & May, C. E. (2012). Chromosome biology. Springer Science & Business Media.
- Ugarković, Đ. I. (2009). Centromere-competent DNA: structure and evolution (pp. 53-76). Springer Berlin Heidelberg.
- Chan, G. K., Liu, S. T., & Yen, T. J. (2005). Kinetochore structure and function. Trends in cell biology, 15(11), 589-598.
- Cleveland, D. W., Mao, Y., & Sullivan, K. F. (2003). Centromeres and kinetochores: from epigenetics to mitotic checkpoint signaling. Cell, 112(4), 407-421.
- By Afunguy at English Wikipedia [Public domain], via Wikimedia Commons
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