Question

If the centromere is situated in the middle of the chromosome, it is called as
A. Metacentric
B. Acrocentric
C. Submetacentric
D. Telocentric

Answer 1

Hint: The chromosomes can be classified as metacentric, submetacentric, acrocentric, and telocentric: based on the centromere location. In the case where the centromere is present at the center of the chromosome, these structures have two identical arms of almost equal length.

Complete answer: Standard chromosomes have one centromere in each. Its position can vary along the chromosome.
1. Metacentric chromosomes have the centromere located halfway between the ends of the chromosome, thus, separating the 2 arms of the chromosome equally.
2. Chromosomes with centromeres positioned visibly slightly off-center are called submetacentric.
3. Acrocentric and telocentric chromosomes have centromeres positioned very near and at the top of the chromosome, respectively.
4. During the metaphase stage in many organisms, when chromosomes are at their most condensed form, it is possible to view the centromere as a constriction under a high-power electron microscope, where the chromatids of the replicated chromosome are held together.

So, the correct answer is option A. Metacentric.

Note: These Metacentric chromosomes are also known as X-shaped chromosomes due to their appearance. In a normal human karyotype, it is found that a total of five chromosomes appear as metacentric. These chromosomes are 1, 3, 16, 19, and 20.