The chromosome in which centromere lies slightly away from the centre is called as Sub-metacentric.
In submetacentric type of chromosome, the centromere lies at some distance away from the midpoint, dividing the chromosomes into two unequal arms.
So, the correct answer is option 'B'.

Sub-metacentric

A chromosome is a thread-like structure found in the nucleus of a cell that carries genetic information. The centromere is a specialized region of the chromosome that plays a crucial role in cell division. It is the point where the two chromatids of a replicated chromosome are attached.

Definition of Sub-metacentric chromosome:
A sub-metacentric chromosome is a type of chromosome in which the centromere is slightly away from the center, dividing the chromosome into two unequal arms. One arm is longer than the other.

Explanation:
- In a sub-metacentric chromosome, the centromere is located between the center and one end of the chromosome.
- The two arms of the chromosome are divided into p-arm (short arm) and q-arm (long arm).
- The p-arm is shorter and the q-arm is longer.
- The centromere's position creates an asymmetrical chromosome with one arm longer than the other.

Example:
An example of a sub-metacentric chromosome is Chromosome 4 in humans. The centromere of Chromosome 4 is slightly away from the center, resulting in two unequal arms.

Importance of Centromere Position:
The position of the centromere is essential for the stability and proper functioning of the chromosome. It determines the shape and behavior of the chromosome during cell division.

Significance of Sub-metacentric Chromosomes:
- Sub-metacentric chromosomes play a role in genetic disorders and diseases.
- Changes in the structure or position of the centromere can lead to chromosomal abnormalities, such as translocations and inversions.
- These abnormalities can disrupt the normal functioning of genes and result in genetic disorders.

Summary:
A sub-metacentric chromosome is a type of chromosome in which the centromere is slightly away from the center, dividing the chromosome into two unequal arms. It plays a significant role in genetic disorders and diseases when abnormalities occur in the structure or position of the centromere.