[Biology Class Notes] on Centromere Pdf [2024]

Introduction to Centromere

A Centromere is essentially a restricted region within the chromosome that participates in the crucial function of cell division in the eukaryotic cells. The DNA structure can have several types and there are different tasks or roles to perform. Here it is worth noting, that this is one of the core and fundamental concepts in the Biology syllabus that is not only important for current learning but also useful for higher studies.

What is a Centromere?

The Centromere is the specific portion within the DNA sequence in the chromosomes that connects the sister chromatids during the period of cell prophase. The chromosomes are basically segregated in the long arm q and the short arm p.

The Functions of Centromere

This is the region which connects the two sister chromatids and is known as the point of attaching the spindle fibres.
During the process of cell division in the eukaryotic cells, the role of the Centromere for cell division is aligning and segregating the chromosomes.
Centromere is responsible for the separation of sister chromatid and adhesion, chromosome movement, mitotic and heterochromatin checkpoint control, microtubule attachment, and other processes.
The Centromeres act as the signal processing centres which regulate the progression of the cell cycle.
The Centromere acts as the vital part in the cell’s formation as it is responsible for binding the newly formed chromosomes that are known as the sister chromatids.

Types of Centromere

These can be divided into two sub-categories, namely

Point Centromeres

In this type, mitotic spindle fibres are connected to particular DNA sequences.
Here, the proteins connect with individual DNAs and make the mitotic spindle fibre bond possible.
In this case, the connection between protein and the DNA is present irrespective of its location and other factors.

Regional Centromeres

Regional centromeres are used mostly in humans and eukaryotic cells.
Here, the DNA sequence does not determine the location of centromeres. Rather, other factors combine to contribute in calculating this site.
To define centromeres of this kind, the epigenetic marks inform the proteins about their location. This is required to make a connection with the mitotic spindle complex.

Interesting Fact

These epigenetic marks are nothing but chemical changes made to the DNA with the use of enzymes. These are easily added or removed to/from the DNA without altering any information present in DNA.

Multiple – Choice Questions

Choose the most appropriate option with respect to the Centromere.

Facilitates even distribution.
Restricted chromosomal region.
Connecting sister chromatids.
Connecting to spindle fibres.

Ans: a

Centromeric proteins are the ones which connect to the Spindle Fibres.

True
False

Ans: b

Initially, centromeric DNAs were identified in

Humans.
Bacteria.
Fungi.
Yeast.

Ans: d

Choose the primary reason which states why Chromosomes are condensed.

For facilitating accommodation.
For facilitating cell division.
To provide cell division in daughter cells.
Always condensed.

Ans: c

Choose the appropriate part option which is critically responsible for even distribution of parental DNA.

Spindle fibre.
Centrioles.
Telomere.
Centromere.