Types of chromosomes

 Based on the position of the centromere



Metacentric chromosome

The metacentric chromosome has its centromere centrally located between the two arms. This gives the chromosome a typical 'V' shape that is seen during the anaphase. The arms of this chromosome are roughly equal in length.

Submetacentric chromosome

The arms of the submetacentric chromosome are said to be unequal in length. This is because the kinetochore is present in the submedian position. This gives rise to the 'L' shape of the submetacentric chromosome.

Telocentric chromosome

Also known as the monarchial type of chromosomes, they have a centromere that is located towards the end of the chromosome. Thus, telocentric chromosomes have a 'rod' shaped appearance.

Acrocentric chromosome

The location of the centromere in the acrocentric chromosome is subterminal (near to telomere). This causes the short arm of the chromosome to become really short making it very difficult to observe. Such chromosome assumes J shape or rod shape during anaphase.

Holocentric chromosome

In holocentric chromosomes, the centromere runs through the entire length of the chromosome. These chromosomes are very common in cells belonging to organisms in the animal and plant kingdom.

Based on the centromere number

Chromosome: Architecture, types, and number

The number of centromeres presents on the chromosome help in determining the type of
chromosome. These different chromosome types based on the number of centromeres are as
follows

Acentric chromosome

Acentric chromosomes are those that lack centromeres, i.e., the centromere is totally absent on
the chromosome. These chromosomes are observed due to the effects of chromosome-breaking
the process like irradiation.

Monocentric chromosome

Monocentric chromosomes are those that contain a single centromere. This type of
the chromosome is present in most organisms.

Dicentric chromosome

Dicentric chromosomes are those that have two centromeres that are present on its arms. These
chromosomes are formed after two chromosomal segments with a centromere each, are fused
end to end. This causes them to lose their acentric fragments, leading to the formation of the dicentric
chromosome.

Polycentric chromosome

Polycentric chromosomes are those that contain more than two centromeres.




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