Difference Between Chromosome and Chromatid (With Table)

Scientific words can often be confusing to comprehend because of their diction similarities. Chromosomes and Chromatids are one such pair of words. Although the two words associate with one another, it is scientifically inappropriate to use them interchangeably because they are considerably different.

Chromosome vs Chromatid

The difference between chromosomes and chromatids is that chromosomes are ribbon-like structures found in the nuclear region or nucleus of the cytoplasm. On the other hand, chromatids are identical halves of a duplicated chromosome. Moreover, chromatids are less condensed as compared to chromosomes, which have a coiled structure. 

Chromosome is derived from the Greek word Chroma and Soma which means colour and body respectively. By definition, a chromosome is a genetic material responsible for all the features and characteristics of organisms. In human beings, chromosomes are divided into two types: autosomes and allosomes. Autosomes are the body chromosomes. Chromosomes are responsible for genetic diversity in sexually reproducing organisms like humans. 

The term chromatid was given by McClung and is derived from the Greek word chroma which means colour. Chromatid refers to the identical copies of the DNA that make up a chromosome. There are two types of chromatids: sister chromatids and non-sister chromatids. Moreover, chromatids may be homozygous or heterozygous. Chromatids are unable to transcribe proteins. But, they are crucial during the meiosis of cell division. 

Comparison Table Between Chromosome and Chromatid

Parameters of ComparisonChromosome Chromatid
DefinitionChromosome refers to a ribbon-like structure found in the nuclear region or nucleus of the cytoplasm. Chromatid refers to an identical half of a duplicated chromosome. 
StructureThe structural composition of chromosomes is thin and ribbon-like.The structural composition of chromatid is fibrous, long, and thin.
DNAIn a chromosome, the DNA molecules are tightly-packed.In a chromatid, the DNA molecule is free and unwounded. 
ReplicationChromosomes are capable of replicating or duplicating themselves.Chromatids are unable to duplicate themselves. 
Present Chromosomes are present throughout the lifetime of all cells. Chromatids come into existence during the interphase. Additionally, they exist only till the metaphase of cell division. 

What is Chromosome?

Chromosome refers to a ribbon-like structure found in the nucleus of the cytoplasm. The composition of a chromosome consists of proteins and a single molecule of Deoxyribonucleic Acid (DNA). It is only during the metaphase of cell cycle that one can observe chromosomes under a light microscope.

In human beings, there are two categories of chromosomes: autosomes and allosomes. The body chromosomes are known as autosomes. On the other hand, the sex chromosomes are allosomes. Additionally, there are 23 pairs of chromosomes in the human body. While 22 pairs of chromosomes are autosomes, there is one pair of allsomes. In total, there are 46 chromosomes in the human body. 

The structure of the chromosome varies according to the phase of the cell cycle. Prokaryotic organisms have a single circular chromosome due to the absence of a specified nuclear region. In contrast, eukaryotic organisms like humans chromosomes are packed into a condensed structure to fit in the nucleus. 

In sexually reproducing organisms like humans, chromosomes play a vital role in ensuring genetic diversity . Chromosomes are the carriers of genetic materials that are essentials for a number of functions such as division and reproduction and protein generation. Chromosomal deformities may cause various chromosomal disorders that are detrimental to an organism. 

What is Chromatid?

Chromatid refers to an identical half of a duplicated chromosome. The duplication of chromosomes results in the formation of two identical halves; each one of these halves is a chromatid. As compared to chromosomes, chromatids are less condensed because chromatids form when chromosomes are uncoiled. 

There are two types of chromatids: sister chromatids and non-sister chromatids. Sister chromatids refer to the chromatids from the same chromosomes. On the other hand, non-sister chromatids refer to the chromatids from two different chromosomes. Additionally, non-sister chromatids connect via chiasmata for the exchange of genetic material. 

Chromatids are mostly homozygous because they are identical. However, they may be heterozygous sometimes when mutations cause a change in either one or both the chromatids. More importantly, chromatids are temporary structures that assist in the process of chromosome duplication and separation. 

Chromatids are unable to transcribe proteins. But, they are crucial during the meiosis of cell division. As a cell divides itself, chromatids separate themselves to form individual chromosomes. This event ensures the genetic diversity within the species as well as genetic variability. Thus, in conclusion, chromatids are less condensed structures crucial for sexual reproduction

Main Differences Between Chromosome and Chromatid 

  1. Chromosome refers to a thread-like structure present in the nuclear region or nucleus of the cytoplasm. In contrast, chromatid refers to an identical half of a duplicated chromosome.
  2. Chromosomes are present throughout the lifetime of all cells. On the other hand, chromatids come into existence during the interphase. Additionally, they exist only till the metaphase of cell division. 
  3. While chromosomes have a thin ribbon-like structure, chromatids have a long and lean fibrous structure. 
  4. Chromosomes are capable of replicating or duplicating themselves. On the other hand, chromatids are unable to replicate themselves. 
  5. In a chromosome, the DNA molecules are tightly packed. In contrast, in a chromatid, the DNA molecule is free and unwounded. 

Conclusion

To sum up, the structure, nature, composition, types, and function of chromosomes and chromatids vary intensely. While chromosomes have a thin ribbon-like structure, chromatids have a long and lean fibrous structure. The genetic information in chromosomes helps to transcribe proteins. However, chromatids are unable to transcribe proteins. More importantly, chromatids are temporary structures that assist in the process of chromosome duplication and separation. 

The structure of the chromosome varies according to the phase of the cell cycle. On the other hand, the same isn’t true for chromatids. Additionally, two identical sister chromatids make up a chromosome. Thus, it is justifiable to conclude that chromosomes and chromatids are different structures of the human body. 

References

  1. https://www.osti.gov/etdeweb/biblio/6937261 
  2. http://symposium.cshlp.org/content/16/13.short 
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