(i) The primary constriction present in the chromosome is called Centromere. On either sides of the Centromere there are disc shaped structures called kinetochores. There are four types of chromosomes based on the position of the Centromere they are Met centricThe chromosome has the Centro mere in the middle forming two equal arms of the chromosome.  Sub-met centricThe chromosome has the Centro mere nearer to one end of the chromosome resulting in the formation of one long arm and another short arm.  AreocentricThe Centromere lies extremely close to one end of the chromosome resulting in the formation of one long arm and the other very short arm.  TelocentricIn this type the Centro mere lies in the terminal end of the chromosome.(ii)