Centromeres and kinetochores:

Centromere-

Centromere is region of chromosome where the two sister chromatids are attached. It is located at the central area of the chromosomes and can located at other location like mid or at different position. On the basis of centromere chromosome can be divided into four different types of chromosomes.

• Metacentric
• Submetacentric
• Acrocentric
• Telocentric

1. Metacentric:

 X- shaped chromosome in which centromere is present at the middle of the chromosome. The two arms of the chromosome are roughly equal.

2. Submetacentric:

Centromere located at the near of middle of the chromosomes so that the arms becomes unequal so they named as short arm and long arm. 

3. Acrocentric :

Centromere present at near of the end of the chromosomes it is J- shaped chromosomes. In human 13, 15, 21, 22 are sat acrocentric chromosomes.

4. Telocentric:

Telocentric chromosome is a type of chromosome whose centromere located at the end. 

 The function of centromere 

•  To provide the foundation of the assembly of kinetochore. 
• During mitosis and meiosis it help in movement of replicated chromosome.
• It is the site of attachment of spindle Fibre. 

It helps in  the adhesion and separation, chromosome movements, microtubule attachment, mitotic check-point in cell division of sister chromatids.

Kinetochore:

It is a protein Disc - shaped structure attached with chromatids. It controls the movement of chromosomes during mitosis and meiosis. Attaches chromosome to the spindle microtubule.