Structure Of A Chromosome
Structure of a chromosome:
Chemically, chromosomes are nucleoproteins containing about 40% DNA, 1-10% RNA, 40-50% basic proteins or histones, and about 10% non histone proteins.
The chromosome is most studied at the metaphase stage; it is also the one that is best known regarding its structure. It is constituted by two chromatids, which are parallel but are joined by the centromere.
Following constitutes Structure of a chromosome
The chromosome has the following structure: satellite, rings, arms, bridge, and centromere (primary constriction). At the same time, they have a secondary constriction or nucleolar organizers, which are the narrowest parts of the arms.
Secondary constriction 1 (nucleolar organisation) contains rDNA and present on the chromosome number 13,14,15,21,22 and y-chromosome of humans.
Secondary constriction 2 location is constant for a particular chromosome, found on the long arms of 1, 19, 13, 16 and y-chromosomes of humans.
Primary constriction (centromere) is central constricted region that contain specific DNA sequence to which kinetochore (disc of protein) is bounded.
Telomeres are protective structures found at the ends of eukaryotic chromosomes. Their function is to avoid losing genetic information. Finally, the chromatin bands or segments are those that appear in the DNA graphics, which allows differentiation of chromosomes using the Bands Pattern method.
Chromonemma is a coiled chromatin that contains single molecule of DNA duplex.
Nuclelous is formed by nucleolar organiser during reconstruction phase after the mitosis.
Satellite is the short part of the chromosome that do not contain thymine in their nucleus acid. Chromosomes that contain satellite are called satellite chromosomes.