The chromosome is the most condensed form of DNA, which remains packed into a thread-like structure. On the other hand, a chromatid is the one-half copy of the newly formed chromosome, joined by the centromere to the original chromosome.
Secondly, the chromosomes are present every time in the nucleus of each cell and thus carry the genetic material. While chromatids form during the cellular division processes of mitosis and meiosis.
We can define Genetics as the study of the genetics or heredity in living organisms. We all know our genetic material is present in the form of deoxyribonucleic acid (DNA) and ribonucleic acid (RNA). DNA is present in both prokaryotic as well as eukaryotic organisms, in prokaryotes, it is present in the cytoplasm of a cell, while in the eukaryote, it is present in the nucleus of a cell.
DNA contains all the secrets that make one person unique from others, whether it is physical, like in looks, height, complexion, or in habits and even internally. So, it is the priority of the cells to keep the DNA safe. DNA has so much information that it could even stretch from the Earth to the Sun four times.
In order to keep all information protected, the DNA is highly organized in its form and comprises four chemicals which are adenine (A), guanine (G), cytosine (C)and thymine (T). These chemical’s base pairs with one another with the help of sugar (ribose) and a phosphate molecule.
The discussion of DNA is vast, and so in this content, we will discuss the two confusing terms, which are ‘chromosome’ and ‘chromatid’. These words often seem identical at first glance, but they are not the same and differ in a few points. So, let us discuss them.
Content: Chromosomes Vs Chromatid
Comparison Chart
| Basis for Comparison | Chromosomes | Chromatid |
|---|---|---|
| Meaning | The chromosome is said as the condensed form of chromatin, which is made of deoxyribonucleic acid (DNA) and proteins known as histones. | Chromatids are said as one of the identical components that form the duplicated chromosome. |
| Condensation | The chromosome is said as the most condensed form of DNA. | A chromatid is less condensed than a chromosome. |
| Occurrence | The chromosome is present throughout the life cycle of a cell. | Chromatid occurs when the cell goes through the mitosis or meiosis. |
| Content | The chromosome contains a single, double-stranded, tightly packed molecule of DNA. | Chromatid contains unwounded, two strands of DNA joining together by a centromere. |
| Structure | A ribbon-like thin structure. | A long and thin structure. |
| Genetic material | The homologous chromosomes are not identical. | Homologous sister chromatids are identical. |
| Stage | Chromosome appears in M phase. | Chromatids appear in interphase. |
| Function | Chromosomes are involved in the allocation of genetic material. | A chromatid is engaged in metabolism and other activities of the cell. It also empowers cells to duplicate. |
Definition of Chromosomes
The chromosome is a structure where the highly condensed form of DNA is present. It is the long thread-like structure that contains the genetic material of organisms. The word has been derived from the Greek words where “chroma” means “colour“, and “soma” means “body“.
The number of chromosomes varies in different organisms, some may have one, while some may have up to hundreds. In the prokaryotic cell, the chromosomes are single circular, free-floating and contain the only chromosome. In the case of eukaryotic organisms, the chromosomes are numerous. The long chain of the chromosome made up of DNA remains associated with histone proteins.
In prokaryotes, the chromosomes are present in nucleoids, which do not have introns and are expressed as operons. The bacteria have the plasmid, which is the extra-chromosomal material. In eukaryotes, the chromosome is stored in the nucleus.
Atlas blue butterfly, found in North Africa, has 448-452 chromosomes. While the Jack jumper ant, a native of Australia, has only one chromosome.
In the case of Humans, in every cell, there are 22 identical pairs of a chromosome (autosomes), except the sex chromosomes, which are X and Y. So there are 48 chromosomes in humans. The ‘Y’ chromosome expresses male characters. Whereas the ‘X’ chromosome is a larger chromosome and contains more genes, and is more dominating too.
Definition of Chromatid
In the cell cycle of the cell, during the S phase, the amount of DNA gets doubled in order to proceed with cell division. So a new copy of a DNA strand is formed, copying the same genetic information as the existing strand. Though the number of chromosomes remains the same in the cell, in the end, each chromosome will have two copies of DNA strands, and one of the strands of DNA is termed a chromatid. Hence, a single DNA strand is a chromatid.
So we can say that the chromatid is one-half of the newly replicated chromosome joined to the original chromosome. The chromatin has a thread-like structure and contains chromatin fibres. The DNA is wrapped around the histones, which are a protein.
Sister chromatids pair are the two chromatids found in the chromosome. These sister chromosomes are joined together by the centromere but get separated further during anaphase. It is the third phase in the mitotic or M phase in the cell cycle.
The chromatids are present in the most condensed form in the cell, and when the sister chromatids get separated, known as daughter chromosomes. Therefore sister chromatids are known to be homozygous.
On the other hand, due to mutations during replication, the newly formed DNA strand makes the sister chromatids heterozygous. Although at the time of sexual reproduction, the maternal and paternal homologous chromosome pairing results in non-sister chromatids.
Key Differences Between Chromosomes and Chromatid
Below are the critical points to exhibit the difference between the chromosome and chromatid:
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The chromosome is a ribbon-like thin structure which contains a condensed form of deoxyribonucleic acid (DNA). Chromatids are long, compact, identical structures of the chromosomes that form during the duplication of the chromosome.
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The chromosomes are the most condensed form of DNA, while the chromatid is less condensed.
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The chromosome is present throughout the life cycle of a cell, whereas chromatid occurs when the cell undergoes mitosis or meiosis.
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The chromosome contains a single, double-stranded, tightly packed molecule of DNA; on the other hand, a chromatid has unwounded two strands of DNA joining together by a centromere.
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Chromosomes regulate the transfer of genetic material, while the role of chromatids is in the metabolism and other activities of the cell. It also empowers cells to duplicate.
Conclusion
In this context, we explore the points on which the chromosome and chromatids differ. We also came to know their role in the cell cycle. As these are present in both prokaryotes and eukaryotes, we can also say that the genetic material must have undergone a significant process of evolution over time.
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