Chromosome

as we all know, the DNA composed of a sequence of nucleotides that takes the form of helix. in humans the DNA is double stranded with the 2 strands run anti-parallel to each other. normally the DNA will binds to a protein; & these proteins will protect the DNA from degeneration by different enzyme in the surrounding environment.
binding of DNA to protein will result in a structure called nucleoprotein  by looping & looping we finally get a Chromosome; which is a condensed structure. but this condensed structure will relax during cell division; one of the famous figures of the chromosome is the one during a meta-phase (link); in the metaphase each chromosome will be made up of 2 chromatids
during cell division; microtubles will be originated from each pole of the cell & will attach to chromatid; then after splitting; cytokinesis will occurs (cytokinesis is the real division of the cell; because it involves the division of both the cytoplasm & plasma membrane & it will produce 2 daughter cells; so that each one will have a chromosome composed of one chromatid; chromatin strucutre (link) )

Centromeres:
all chromosomes have a constriction where proteins (MT) binding to during metaphase & pull chromatids apart from each other --this constriciton is called centromere; usually the centromere is not located at the center of the chromosome; so it will split the chromosome into 2 pieces have following symbol :

• P: Petit --- the small pieces 
• q: grand --- the longer pieces

centromeres also used to classify the chromosome into:

• metacentric; referring to a central centromere 
• acrocentric; referring to Terminal centromere 
• submetacentric; the Centromere is above or below the center

Telomeres:
periphery of the Chromosome; its the tip of each chromosome; consists of tandem repeats (TTAAGGG)