The key difference between centromere and chromomere is that centromere is a constricted region that joins sister chromatids together in a chromosome while chromomere is a linearly arranged bead-like structure present along the length of the chromosome.
A chromosome is a threadlike structure composed of nucleic acids and proteins. They contain the genetic information of an organism. There are several distinct regions in a chromosome, including chromatids, centromere, chromomere and telomere. The centromere is the visible point of constriction in the chromosome. It joins sister chromatids together and is important during the cell division. In contrast, chromomeres are tightly coiled chromatin present along the length of the chromosome. They appear as beads on a string. They carry genes during inheritance.
CONTENTS
1. Overview and Key Difference
2. What is Centromere
3. What is Chromomere
4. Similarities Between Centromere and Chromomere
5. Side by Side Comparison – Centromere vs Chromomere in Tabular Form
6. Summary
What is Centromere?
Centromere is the structure that connects two chromatids together in a chromosome. It is a visible point of constriction in the chromosome. Centromere contains repeated sequences of DNA and specific proteins. These proteins create a disk-shaped structure called kinetochore at the centromere. Kinetochores are involved in cell signalling for the progression of the cell cycle, and it serves as the main attachment site for spindle microtubules.
Figure 01: Centromere
Centromeres are of two types as regional centromeres and point centromeres. Point centromeres establish a single direct line of attachment per chromosome and bind to different specific proteins. These proteins recognize highly efficient DNA sequences. But regional chromosomes establish multiple attachments per chromosome. Regional centromeres are more prevalent in cells of organisms rather than point centromeres.
Depending on the position of the centromere in a particular chromosome and the length of the arms of the chromosome, there are six different types of chromosomes. They are acrocentric, sub-metacentric, metacentric, telocentric, dicentric and acentric.
What is a Chromomere?
Chromomere or idiomere is a linearly arranged bead-like structure present along the length of the chromosome. They appear as beads on a string. They are regions of tightly folded DNA or masses of coiled chromatin. Hence, they are visible as dark staining bands. However, they are visible on a chromosome during the prophase of meiosis and mitosis. The distribution of chromomeres is characteristic to a particular chromosome. Most importantly, the position of chromomeres is constant for a particular chromosome. Moreover, the pattern of distribution is different among chromosomes. Hence, they provide a unique identity for each homologous chromosome pair.
Figure 02: Chromomere
Chromomeres contain genes or gene clusters within their structures, and they are responsible for carrying genes during inheritance. Chromomere maps are important in genetics and chromosome studies. They are useful when finding the exact locations of genes on a chromosome. Moreover, chromomeric maps are useful in analyzing chromosomal aberrations.
What are the Similarities Between Centromere and Chromomere?
- Centromere and chromomere are two parts seen in eukaryotic chromosomes.
- The positions of centromere and chromomere are constant for a particular chromosome.
- Both parts carry out important functions in eukaryotes.
What is the Difference Between Centromere and Chromomere?
Centromere is a specific DNA sequence that joins two sister chromatids of a chromosome together while chromomere is a bead-like masses of coiled chromatin present along the length of the chromosome. So, this is the key difference between centromere and chromomere. Also, centromeres are found mostly at the middle of the chromosome while chromomeres are present along the lengths of the whole chromosome.
Another difference between centromere and chromomere is the functions they carry out. Centromere links a pair of sister chromatids. It also provides a site for spindle fibre attachment during mitosis and meiosis. In contrast, chromomeres contain genes or gene clusters, and they carry genes during inheritance. We can see one or two (most probably) centromeres in one chromosome while there are many chromomeres in one chromosome.
Below infographic shows more comparisons related to the difference between centromere and chromomere.
Summary – Centromere vs Chromomere
Centromere is a constricted region on a chromosome that links two sister chromatids together. It is made up of specialized DNA sequence, and it is essential for the segregation of chromosomes. Moreover, centromeres enable the equal segregation of genetic material into daughter cells during cell division. During the cell division, the centromere is functional while the other parts remain inactive. On the other hand, chromomeres are the bead-like structures arranged vertically along the length of the chromosomes. They are masses of coiled chromatin. They are responsible for carrying genes during inheritance. Thus, this summarizes the difference between centromere and chromomere.
Reference:
1.”6 Main Parts Of A Chromosome”. Biology Discussion, 2020, Available here.
2. “Chromomere”. En.Wikipedia.Org, 2020, Available here.
Image Courtesy:
1. “Condensed Eukaryotic Chromosome” By Zephyris at the English language Wikipedia (CC BY-SA 3.0) via Commons Wikimedia
2. “Drosophila polytene chromosomes 2” By J. Albert Vallunen (User:albval) – Own work (CC BY-SA 2.5) via Commons Wikimedia