What Is a Chromatid

Chromatid is the term used to refer to each of the strands of replicated chromosome. One has to understand the fact that there is major difference between the two terms, ‘chromatid’ and ‘chromosome’. The chromatids that are exact copies of each other are joined at the center and this point of joining of the two chromatids is referred to as centromere. Both the chromatids at this stage are referred to as daughter chromatids and both of them have the same genetic composition. At a later stage, the chromatids get separated from each other and following this each of the individual chromatids are referred to as daughter chromosomes.

Each chromatid has a long arm and a short arm. The section of the chromatid below the centromere is referred to as ‘long arm’ and the section above is called ‘short arm’ of the chromatid. The process of separation of the chromatids at the centromere takes place at the process of cell division. In mitosis, the separation takes place at the stage of anaphase and in meiosis, the division of the chromatids into two happens at anaphase 2.It is to be noted that a pair of sister chromatids is termed a ‘dyad’ and they are produced in the prophase 1 stage of the meiosis process.

One has to note the point that in case of meiosis, the sister chromatids so formed, appear to have an undivided structure with the centromere being the common point of contact. But the scenario is different in mitosis, where each of the sister chromatids seem to have a separate centromere. The process of replication and separation of the chromatids is an important aspect and irregularities of any kind here can lead to problems to the person in the future. Ailments like Down syndrome and other chromosomal disorders are said to be due to the irregularities that take place during the process of cell division wherein the chromatids separate into daughter chromosomes.

It would be worth noting here that the term, chromatid was first proposed by the scientist Clarence Erwin McClung in the year 1900. The chromatids that are joined by a centromere can either be ‘sister chromatids’ or ‘non sister chromatids’. In the process of meiosis, chances of genetic recombination are high owing to the fact that crossing over takes place between the two ‘non sister chromatids’.

All in all, the chromatids are the building blocks of the beginning of life and thus, studying about them helps the biologists in getting a clear idea about the irregularities of any kind that show up due to problems in cell division.