The key difference between chromosome and chromatid is that a chromosome is a long thread-like form of a DNA molecule while a chromatid is one-half of two identical copies of a replicated chromosome. In fact, two chromatids are joined together by a centromere to form a chromosome.
Chromosome and chromatid are closely related structures that are made from DNA molecules. Chromosomes contain genetic information in the form of specific DNA sequences or genes. A single strand of DNA is called a chromosome and two chromatids will form a single chromosome. Chromosomes are vectors or carriage of genetic materials of one organism to the other while chromatids enable these cells to duplicate.
CONTENT
1. Overview and Key Difference
2. What is a Chromosome
3. What is a Chromatid
4. Similarities Between Chromosome and Chromatid
5. Side by Side Comparison – Chromosome vs Chromatid in Tabular Form
6. Summary
What is a Chromosome?
Chromosomes are the thread-like form of DNA molecules present in the nucleus of every cell in our body. In a human cell, there are a total of 46 individual chromosomes. They are in 23 homologous chromosome pairs. The pairing of the 46 chromosomes occurs during the two cell division processes: meiosis and mitosis.
Figure 01: Chromosomes during Mitosis
According to the German biologist, Theodor Heinrich Boveri, chromosomes are vectors of heredity.
What is a Chromatid?
Chromatid is one of the two similar copies of DNA that makes up a single chromosome. One chromosome has two chromatids joined by a centromere. During the cell division (meiosis and mitosis), they are separated from each other; they are then called sister chromatids since they are identical to each other.
Figure 02: Chromatid and Chromosome
To be more specific, a chromosome is like an X shape structure when viewed under a microscope. Divide the X by half and it would result in two identical parts > and <. A single > or < is what you call a chromatid. The center point of contact is the centromere and the whole X is the chromosome.
What are the Similarities Between Chromosome and Chromatid?
- Chromosomes and chromatids are formed by DNA molecules.
- They are present within the nucleus.
- Both contain genetic information and involve with heredity.
- They are associated with histone proteins.
What is the Difference Between Chromosome and Chromatid?
Chromosome is a coiled thread-like structure that contains the genetic material of organisms while chromatid is each of the two identical copies that make the chromosome. This is the key difference between chromosome and chromatid. One more difference between chromosome and chromatid is that the chromosomes carry genetic information of an organism whereas the chromatids allow DNA duplication. Furthermore, chromosomes contain tightly coiled DNA while chromatids contain unwound DNA.
The below infographic presents the difference between chromosome and chromatid in tabular form for quick reference.
Summary – Chromosome vs Chromatid
A chromosome is a long and continuous strand of DNA. A duplicated chromosome has two identical sister chromatids. Hence, a chromatid is one of the two identical copies of a duplicated chromosome. Chromosomes are the vectors of heredity. In other words, it carries genetic information which passes from parent to offspring. Overall, this is the difference between chromosome and chromatids.
Reference:
1. “Chromosomes, chromatids and chromatin” Khan Academy, Available here.
Image Courtesy:
1. “Chromosomes during mitosis” By SyntaxError55 at the English language Wikipedia (CC BY-SA 3.0) via Commons Wikimedia
2. “0330 Homologous Pair of Chromosomes” By OpenStax – (CC BY 4.0) via Commons Wikimedia