The key difference between chromatin and chromosomes is that chromatin is untangled and unfolded DNA that exists as a complex of DNA and histone proteins while chromosomes contain the highest condensed structure of the DNA double helix for the proper separation of the genetic material between daughter cells.
Chromatin and chromosome are two categories of structures of the double helix of DNA that are present in different stages of the cell. It is essential to pack the whole DNA that stores genetic information of the cell into the eukaryotic nucleus for existence. Hence, chromatin is the usual form of packaged DNA within the cell. On the other hand, chromosomes are the most important structures in the cell during cell division, and they contain the genetic material in the form of DNA. This is because they are responsible for the transmission of hereditary information from one generation to the next. There are two types of chromosomes as autosomes and sex chromosomes. Sex chromosomes are important in sex determination while autosomes determine the other characteristics. Generally, chromosomes appear during metaphase of cellular division.
CONTENTS
1. Overview and Key Difference
2. What is Chromatin
3. What are Chromosomes
4. Similarities Between Chromatin and Chromosomes
5. Side by Side Comparison – Chromatin vs Chromosomes in Tabular Form
6. Summary
What is Chromatin?
Chromatin is a complex of DNA and histone proteins. Generally, chromatin contains an equal mass of DNA and proteins. Chromatin appears as thin, long thread-like structures. The main function of chromatin is the easy package of genetic information of the cell into the eukaryotic nucleus for existence. Apart from packaging, chromatin also allows DNA replication by regulating gene expression. Moreover, it prevents DNA damage.
Figure 02: Chromatin
Nucleosomes are the basic units of chromatin. These are the core particles and the the linker DNA interconnects these particles. Also, the core particles form by wrapping 150-200 long DNA strands around the core of histone proteins. Each nucleosome core particle contains eight histone proteins.
Furthermore, chromatin appears during the interphase of the cell cycle. It contains two types: heterochromatin with inactive DNA to provide structural support to the genome, and euchromatin with actively expressed genes in the genome.
What are Chromosomes?
A chromosome is the highest condensed structure of DNA double helix associated with histone proteins. In certain genomes, they contain more than a set of chromosomes. Hence, we call these copies of the same chromosome homologous chromosomes. In the human body, 46 chromosomes are present in the genome in 23 pairs of homologous chromosomes along with two sex chromosomes.
Each chromosome contains centromeres, telomeres, and an origin of replication apart from genes. The initiation of DNA replication happens at the origin of this replication. Once replicated, chromosomes contain two sister chromatids held together by a centromere. We call the long arm of the chromosome the q arm, and the shorter arm is the p arm.
Figure 02: Chromosome
According to the type of centromere, there are four types of chromosomes. They are telocentric, acrocentric, submetacentric and metacentric chromosomes. Furthermore, during the study of chromosomes, the nuclear division is arrested at metaphase since chromosomes are nicely visible in this phase.
What are the Similarities Between Chromatin and Chromosome?
- Both chromatin and chromosome contain DNA.
- We often associate these two with histone proteins.
- Moreover, both contain genetic information of the cell.
What is the Difference Between Chromatin and Chromosomes?
Chromatin and chromosome are two types of DNA arrangements in a cell. Chromatin is untangled and unfolded DNA that exists as a complex of DNA and histone proteins while chromosomes contain the highest condensed structure of the DNA double helix. This is the key difference between chromatin and chromosomes. Furthermore, chromatins are visible during the interphase of the cell cycle while chromosomes are visible during the metaphase of the cell cycle. Therefore, this is another difference between chromatin and chromosomes. Another difference between chromatin and chromosomes is their structure. Chromatins are thin, long, uncoiled structures while chromosomes are thick and compact ribbon-like structures.
The following infographic summarizes the difference between chromatin and chromosomes.
Summary – Chromatin vs Chromosome
Chromatin and chromosome are two types of DNA present in different stages of the cell. DNA, RNA, and histone proteins are the building material of chromatin. Two types of chromatin are euchromatin and heterochromatin. On the other hand, a chromosome is the highest condensed structure of DNA double helix present inside the nucleus. Each chromosome contains centromeres, telomeres and an origin of replication apart from genes. Chromatins are condensed 50 times than the normal DNA double helix while chromosomes are condensed 10,000 times than the normal DNA double helix. Thus, this is the difference between chromatin and chromosomes.
Reference:
1. “Chromatin Structure and Function: a Guide.” Abcam, 29 Jan. 2019, Available here.
2. “What Is a Chromosome? – Genetics Home Reference – NIH.” U.S. National Library of Medicine, National Institutes of Health, Available here.
Image Courtesy:
1. “Sha-Boyer-Fig1-CCBy3.0” (CC BY 3.0) via Commons Wikimedia
2. “Chromosome” By derivative work: Tryphon (talk)*Chromosome-upright.png: Original version: Magnus Manske, this version with upright chromosome: User:Dietzel65 – This is a retouched picture, which means that it has been digitally altered from its original version. Modifications: Made a SVG file inspired by this picture.. The original can be viewed here: Chromosome-upright.png. Modifications made by Tryphon (CC BY-SA 3.0) via Commons Wikimedia