Question

Classify the chromosomes on the basis of position of centromere.

Answer 1

The long structure of DNA is coiled to a great extent to fit inside a tiny nucleus. This process of coiling gives rise to a chromatid structure (it is a thread-like structure) and these chromatids give rise to chromosomes after supercoiling which can be seen during the cell division. There are various types of chromosome depending upon position of centromere.

Complete answer:
Chromosomes are the bundles of tightly coiled DNA located within the nucleus of almost every cell.
All chromosomes are not exactly like one another. There are several types of chromosomes depending upon shapes and function.
Two elongated structures are called arms of the chromosomes . Both of them are attached to each other by a knot-like structure between them called Centromere. One is the ‘p’ arm and the other one is called the ‘q’ arm. Smaller arm is the ‘p ’ arm while the larger one is the ‘q’ arm .
In non duplicated chromosomes. There is one ‘p’ and ‘q’ arm while in duplicated chromosomes there are two ‘p’ and ‘q’ arms.
On the basis of position of centromere, There are four types of chromosomes:

1. Metacentric : in this type centromere is placed exactly at the centre and two arms (‘p’ and ‘q’ ) of same length.
2. Sub-metacentric: Here, the centromere is placed slightly away from the centre as a result the two arms of the chromosomes appear unequal .
3. Acrocentric: The term ‘Acro’ in greek relates to peak. In this the centromere is placed almost toward the end of the chromosomes.
4. Telocentric: in this case the centromere is present at the extreme end, that is the centromere is placed at the telomeric region. However, Human karyotype lacks telocentric chromosomes.

Note: Karyotype: it is the number and appearance of chromosomes in the nucleus of the eukaryotic cell. Karyotype describes the chromosome count of the chromosome. Its length, position of centromere.
The study of a whole set of chromosomes are called Karyology . The study of karyotypes is important for cell biology and genetics and the results may be used in evolutionary biology and medicine.
Karyotypes can be used for various purposes such as chromosomal aberration, cellular function, taxonomic relationship and to gather information about past evolutionary events.