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.

Ans: b

Choose the accurate number of satellite sequence elements in yeast centromere.

Ans: a

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FAQs on Centromere

1. What exactly is a centromere and where is it located on a chromosome?

A centromere is the specialised DNA region of a chromosome that appears as a primary constriction or a narrow waist. It plays a crucial role in holding the two sister chromatids together. While often found near the centre of a chromosome, its exact position can vary, which helps in classifying different types of chromosomes.

2. What is the main function of the centromere during cell division?

The primary function of the centromere is to ensure the correct segregation of chromosomes during cell division (mitosis and meiosis). It serves as the attachment point for spindle fibres via a protein complex called the kinetochore, which pulls the sister chromatids apart to opposite poles of the cell.

3. What are the four main types of centromeres based on their position?

Chromosomes are classified into four types based on the position of the centromere:

Metacentric: The centromere is in the middle, forming two equal arms.
Sub-metacentric: The centromere is slightly away from the centre, creating one shorter and one longer arm.
Acrocentric: The centromere is located very close to one end, resulting in one extremely short and one very long arm.
Telocentric: The centromere is at the terminal end of the chromosome.

4. How is a kinetochore different from a centromere?

A common point of confusion is the difference between a centromere and a kinetochore. The centromere is the specific region of DNA on the chromosome. The kinetochore is a large protein structure that assembles on top of the centromere. Essentially, the centromere is the 'docking station', and the kinetochore is the 'dock' where spindle fibres actually attach.

5. What is the difference between a centromere and a centrosome?

Although their names sound similar, they are completely different structures. A centromere is a part of a chromosome. In contrast, a centrosome is an organelle found in the cytoplasm of animal cells that organises microtubules and is responsible for forming the spindle poles during cell division.

6. Why is the proper function of a centromere critical for an organism?

The proper functioning of the centromere is vital for genetic stability. It ensures that each new daughter cell receives an exact, complete set of chromosomes. If the centromere fails to function correctly, it can lead to an improper number of chromosomes in the daughter cells (a condition called aneuploidy), which is often the cause of genetic disorders and cell death.

7. What is the basic structure of the DNA in the centromere region?

The DNA within the centromere is typically a type of highly condensed and repetitive DNA known as heterochromatin. This specific structure helps it perform its unique role of binding to kinetochore proteins and withstanding the pulling forces of the spindle fibres during cell division.