Difference Between Centromere and Telomere

Key Difference – Centromere vs Telomere
 

Chromosomes are the threadlike structures of nucleic acids and proteins that carry the genetic information of an organism. Chromosomes are located within the nucleus of eukaryotic organisms while in prokaryotes, they are found in the cytoplasm. Genetic information is hidden inside the chromosomes in the form of genes. Genes are the specific DNA molecules that transcribe and translate into proteins that are necessary for all the functions of an organism. A chromosome is made from different regions of DNA and protein molecules. Centromere and telomere are two specific regions that are very important for the functioning of chromosomes. These two regions are made from similar DNA sequences. But they differ from several other features. The centromere is the region of a chromosome that is the centre that determines the kinetochore formation and cohesion of sister chromatids. A telomere is the end region of chromosomes that are important for the protection of chromosome ends from the breakages and prevention of chromosomes joining with each other.  The key difference between the centromere and telomere is the location of each region. The centromere is located at the centre of the chromosome while telemore is located at the ends of the chromosomes.

CONTENTS

1. Overview and Key Difference
2. What is Centromere
3. What is Telomere
4. Similarities Between Centromere and Telomere
5. Side by Side Comparison – Centromere vs Telomere in Tabular Form
6. Summary

What is Centromere?

The centromere is a region of a chromosome that comprises of specialized DNA sequence and protein complexes. It is located mostly in the centre of the chromosome. This is a highly important region since it determines the kinetochore formation. The kinetochore is a complex of proteins associated with the centromere. It is necessary during the cell division. Microtubules of the spindle fibres attach to the kinetochore, and it helps to pull the sister chromatids apart during the cell division. Proteins of the kinetochore help the centromere to hold the sister chromatids together in the chromosomes.

Centromere is the specific region that links the sister chromatids of the chromosomes. Based on the position of the centromere, chromosomes are categorized into four main types. They are metacentric, submetacentric, acrocentric and telocentric chromosomes. Centromere is located in the exact middle position of the chromosome in metacentric type. Hence, two arms of the metacentric chromosome are in equal lengths, and they are X shaped chromosomes. In submetacentric chromosomes, the centromere is located very closure to the middle but not exactly at the centre. Hence, two arms of the submetacentric chromosomes are not equal, but very closure in length and they are L shaped chromosomes. Acrocentric chromosomes have very short p arm that is hard to observe. In telocentric chromosomes, centromere is located at the end of the chromosome. They show a shape similar to letter “i” during anaphase.

What is Telomere?

Telomeres are the extreme ends of eukaryotic chromosomes. They are composed of repeating DNA sequences and multiple protein components. Telomeres can posses hundreds to thousands of same repeating sequence. They act as protective caps of the chromosome ends. Telomeres prevent loss of base pair sequences by the enzymatic degradation from the chromosome ends. Further, telomeres prevent fusing of chromosomes with each other and maintain the stability of the chromosomes.

DNA at very ends of the chromosomes cannot be fully copied in each time of the replication. It can cause for shortening of the chromosomes when passing into next generation. However, telomere arrangement at tips of the chromosomes facilitates the complete replication of linear DNA. Proteins associated with the telomere ends are also important in protecting chromosomes and preventing them from triggering DNA repair pathways.

The nucleotide sequence of the telomere region differs among the species. It consists of noncoding tandemly repeated sequences. Length of the telomeres also varies among the different species, different cells, different chromosomes and according to the age of the cells. In humans and other vertebrates, commonly found repeating sequence unit in the telomeres is TTAGGG.

What are the Similarities Between Centromere and Telomere?

• Both centromere and telomere are regions of chromosomes.
• Both centromere and telomere regions are made from DNA sequences and proteins.
• Both centromere and telomere regions are important for the overall functioning of the chromosomes.

What is the Difference Between Centromere and Telomere?

Summary – Centromere vs Telomere

Centromere and telomere are two regions of a chromosome. Centromere is composed of specialized DNA sequence, and it is the site of kinetochore formation. The kinetochore is important in the attachment of spindle fibres during the cell division, and it helps centromere to hold sister chromatids of the chromosomes. Telomere is positioned at the extreme ends of the chromosomes. They are made up of repeating sequences. They act as protective caps of the chromosome ends. Telomeres prevent the loss of base pairs from the chromosome ends and ensure the complete replication of linear DNA. This is the difference between centromere and telomere.

Reference:

1.“Telomere.” Wikipedia, Wikimedia Foundation, 28 Feb. 2018. Available here 
2.“Centromere.” Wikipedia, Wikimedia Foundation, 28 Feb. 2018. Available here  

Image Courtesy:

1.’Chromosome’By User:Dietzel65 (CC BY-SA 3.0) via Commons Wikimedia
2.’Telomere’ (CC BY-SA 3.0) via Commons Wikimedia