What is a centromere? How does the position of the centromere form the basis of the classification of chromosomes? Support your answer with a diagram showing the position of the centromere on different types of chromosomes.

(N/A) centromere is a primary constriction present on the chromosomes where the chromatids are held together.
Chromosomes are divided into four types based on the position of the centromere:
$(i)$ Metacentric chromosome: The chromosome in which the centromere is present in the middle and divides the chromosome into two equal arms.
$(ii)$ Sub-metacentric chromosome: The chromosome in which the centromere is slightly away from the middle region,resulting in one arm being slightly longer than the other.
$(iii)$ Acrocentric chromosome: The chromosome in which the centromere is located close to one of the terminal ends,resulting in one extremely long arm and one extremely short arm.
$(iv)$ Telocentric chromosome: The chromosome in which the centromere is located at one of the terminal ends.