Difference Between Metacentric and Telocentric Chromosomes

The key difference between metacentric and telocentric chromosomes is that in metacentric chromosomes, the centromere is located in the middle of the chromosome while in telocentric chromosomes, the centromere is located at the end of the chromosome.

A chromosome is a thread-like structure made from DNA and histone proteins. They contain genetic information of an organism. There are several distinct regions of a chromosome, including chromatids, centromere, chromomere and telomere. The centromere is the visible point of constriction in the chromosome which joints sister chromatids together. It is important during cell division. Depending on the position of the centromere in a particular chromosome, there are six different types of chromosomes: acrocentric, sub-metacentric, metacentric, telocentric, dicentric and acentric.

CONTENTS

1. Overview and Key Difference
2. What are Metacentric Chromosomes
3. What are Telocentric Chromosomes
4. Similarities Between Metacentric and Telocentric Chromosomes
5. Side by Side Comparison – Metacentric vs Telocentric Chromosomes in Tabular Form
6. Summary

Metacentric chromosomes are the chromosomes in which the centromere is located in the middle position of the chromosome. Centromere holds the two sister chromatids together in place. In addition, the centromere is involved in the spindle formation process during the cell division. The centromere binds to the kinetochore proteins to form the spindle apparatus during both mitosis and meiosis.

Figure 01: Metacentric Chromosome

Owing to the structure of the metacentric chromosomes, they are composed of two equal-sized arms. They appear as ‘v’ shaped structures during the metaphase of the cell division. The presence of metacentric chromosomes is mostly observed in primitive organisms. Karyotyping using Giemsa staining has enabled cytogeneticists to characterize these chromosomes. Symmetric karyotype refers to the karyotyping done on primitive organisms to observe metacentric chromosomes. Besides, human chromosomes 1 and 3 are metacentric chromosomes. Amphibians mainly have metacentric chromosomes.

What are Telocentric Chromosomes?

Telocentric chromosomes are the rarest type of chromosomes. They are not found in humans. They can be found in very few species such as mice. In telocentric chromosomes, the centromere is placed at the extreme end or at the tip of the chromosome. Therefore, telocentric chromosomes do not possess characteristic p and q arms seen in the chromosome structure. These chromosomes have only one arm; hence, they appear as a rod-like structure.

Figure 02: Placements of Centromere
(I: Telocentric II: Acrocentric III: Submetacentric IV: Metacentric – A: Short arm (p arm) B: Centromere C: Long arm (q arm) D: Sister Chromatid)

Moreover, this is named as “telocentric chromosome” because centromere is situated in the telomeric region of the chromosomes. The structure of the telocentric chromosome can be deduced by karyotyping after Giemsa staining.

• Metacentric and telocentric chromosomes are two different types of chromosomes categorized based on the position of the centromere.
• They can be visualized and identified by karyotyping using Giemsa staining.
• Chromosomes are composed of DNA and histone proteins.

Metacentric chromosomes have their centromere at the centre of the chromosome while telocentric chromosomes have their centromeres at one end. So, this is the key difference between metacentric and telocentric chromosomes. Furthermore, the metacentric chromosomes have two arms that are equal in length. But, telocentric chromosomes do not have two arms. They have only one characteristic arm.

Moreover, another difference between metacentric and telocentric chromosomes is that the metacentric chromosomes appear as X shaped while the telocentric chromosomes appear as i-shaped or rod-shaped.

Below infographic tabulates more differences between metacentric and telocentric chromosomes.

Summary – Metacentric vs Telocentric Chromosomes

Chromosomes are found within the nucleus in eukaryotes, and they contain the genetic information of the organism. Metacentric, submetacentric, acrocentric, and telocentric are the four types of chromosomes. In metacentric chromosomes, centromere is found in the middle. In telocentric chromosomes, centromere is found at one end. Thus, this is the key difference between metacentric and telocentric chromosomes. In metacentric chromosomes, two arms are equal in length. In telocentric chromosomes, two arms cannot be distinguished. Moreover, telocentric chromosomes are very rare and not found in humans.

Reference:

1. “Telocentric, Acrocentric And Metacentric Chromosomes | Easy Biology Class”. Easybiologyclass.Com, 2020, Available here.

Image Courtesy:

1. “156403” (CC0) via Pixabay (Cropped)
2. “Centromere Placement” By Fockey003 – Own work (CC BY-SA 4.0) via Commons Wikimedia

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