Difference between Homologous Chromosomes and Sister Chromatids

In eukaryotes, chromosomes are fixed, self-replicating components of the cell nucleus. DNA and chromosomes carry genetic information from one generation to the next. Depending on the species, the number of chromosomes might be different. Humans, like many other animal and plant species, are diploid creatures (2n), meaning that the chromosomes are organized into sets of two. By using an optical microscope, scientists can observe chromosomes as they duplicate (metaphase).

Each metaphase chromosome is made up of two components termed sister chromatids. They're both identical since DNA is copied throughout cell division.

What are Homologous Chromosomes?

Homologous chromosomes are present in twos in diploid cells. Size, shape, and the positioning of the centromeres on the two homologous chromosomes are also quite similar. It's also the same kind of genetic data that they both carry. When a species reproduces sexually, one set of homologous chromosomes comes from the male parent and the other set comes from the female parent. There are 46 chromosomes in total, with 23 sets of identical chromosomes in each somatic cell of a human being. Among these 23 chromosomes are the sex-defining X and Y chromosomes.

Over the majority of its existence, a cell's chromosomes are each made up of a single DNA molecule. As a cell divides, the DNA molecule copies itself into two copies called sister chromatids. S-phase interphase prophase kinetochores originate at a specific phase of the cell cycle and cellular maturation. In other times, the chromosome exists as a single strand with a centromere pinch at one end. The chromosome is in two halves due to the centromere. A kinetochore is a structure that forms at the periphery of the cell, around the centromere. In the process of cell division, it acts to anchor microtubules to the segregating chromatids.

Metacentric chromosomes are those having a pair of identical arms. Submetacentric chromosomes are those in which one of the arms is obviously longer than the other. Another type of chromosome is the so-called acrocentric variety, in which a secondary pinching creates a break between a little satellite segment and the rest of the chromosome. Specifically, human cells include chromosomes 13, 14, 15, 21, and 22.

What are Sister Chromatids?

The cell must duplicate its chromosomes before it may divide. Sister chromatids are the two identical copies of a chromosome. Cohesin proteins act as bridges between the sister chromatids, which are otherwise identical. In the so-called centromere, a region of the DNA crucial for the subsequent phases of cell division, the sister chromatids are joined. During cell division, it serves as a connection point for the chromosomes and the spindle apparatus, two cytoskeletal structures in eukaryotic cells. Its purpose is to ensure that daughter cells have distinct sets of chromosomes.

Although though the centromere connects the sister chromatids, we still think of them as a single chromosome. When cells divide, daughter cells become independent. When this happens, each chromatid becomes an own chromosome in its corresponding daughter cell.

Differences: Homologous Chromosomes and Sister Chromatids

The following table highlights the major differences between Homologous Chromosomes and Sister Chromatids −


Homologous Chromosomes

Sister Chromatids


Homologous chromosomes are a couple of one maternal and one paternal chromosome, paired up during fertilization in a diploid cell.

The two copies of one chromosome, linked together in the centromere are called sister chromatids.


In sexually reproducing species, one of the homologous chromosomes comes from the father’s gametes and the other one – from the mother’s gametes.

In sexually reproducing species, each sister chromatid comes from either the father’s or mother’s gametes.


The homologous chromosomes are similar in size, shape, and centromere location. The type of genetic information they carry is also similar.

Sister chromatids are identical.


For most of the cell’s life, each chromosome is composed of one DNA molecule. In preparation for cell division, the DNA molecule doubles.

Each sister chromatid is composed of one DNA molecule.


The homologous chromosomes are not connected with each other.

The sister chromatids are linked to each other by proteins called cohesions, via the centromere.


Homologous chromosomes and sister chromatids are two important concepts in genetics and cell division. While they may seem similar, they have distinct differences in terms of their structure, function, and origin.

Understanding the difference between homologous chromosomes and sister chromatids is important in understanding the mechanisms of heredity and cell division.

Updated on: 18-Apr-2023


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