Difference Between Homologous and Non Homologous Chromosomes

An Introduction to Chromosomes: Explaining Homologous and Non Homologous Chromosomes

To grasp the distinction between homologous and non-homologous chromosomes, it’s important to understand what chromosomes are, as well as their structure and function.

Meaning of Chromosomes

Chromosomes hold the genetic material present in every cell. They are located inside the nucleus of a eukaryotic cell. They are structured similarly to threads. DNA and associated proteins called histones make up chromosomes in eukaryotic cells. They are responsible for the hereditary traits passed down from parents to offspring across generations. DNA carries the instructions for specific proteins and is the basis for variations both within and among different species. The term “chromo” means colour and “soma” means body; scientists named these structures chromosomes because they are stained with colour.

Structure of Chromosomes

The structure of chromosomes is quite intricate. The foundation of this structure consists of DNA, or deoxyribonucleic acid. DNA is composed of two chains of nucleic acid base pairs. The base pairs in DNA include cytosine, adenine, thymine, and guanine. The two DNA strands twist into a helical shape due to the complementary pairing between each base and its partner on the opposite strand. Guanine bonds with cytosine, whereas adenine bonds with thymine. The strands are held together by a phosphate-deoxyribose backbone that runs along the sides of the bases.

Function of Chromosomes

Aside from the genetic code contained in the chromosome, many of the proteins that are used in the expression of the chromosomes are also present. The complexity of its shape in terms of how frequent and which genes are translated depends on the degree of intricacy of the chromosome. Gene expression is the procedure that leads to the development of living organisms. The speed at which a gene will be expressed depends on how tightly the pack of the chromosome is packed at a particular locus.

What are Homologous and Non Homologous Chromosomes?

Homologous Chromosomes: 

Two DNA molecules, known as homologous chromosomes, one from each of the two parents, carry the same genes in a diploid animal. Both parents contribute to the whole genome. Identical 23 chromosomes on each of the two parents carry the identical genes. Our cells contain an aggregate of 46 chromosomes in two copies in total. However, each gene may have a variant form on each of the homologous chromosomes. More variation is produced, the negative impacts of mutations are diminished, and populations are typically stabilised when each gene has two copies.

Functions of Homologous Chromosomes:

During gametes production, homologous chromosomes engage in a process known as homologous recombination. When they approach one another, homologous chromosomal segments exchange themselves such that sometimes the process is often termed “crossing over.” All genes are of equal length and size, and they are all present. Between chromosomes, these segments are simply transferrable.

Non Homologous Chromosomes: 

Non-homologous chromosomes are those that are not in the same pair. The form of the chromosome, in other words, the length of the arms and the position of the centromere differs generally in non-homologous chromosomes. Therefore, in meiosis, non-homologous chromosomes do not pair. Only the homolog of a specific organism’s chromosome pairs with other chromosomes. The Law of Segregation states that pairs of homologous chromosomes within the nucleus divide and move apart from other chromosomes.

Functions of Non Homologous Chromosomes:

A complete set of genes is present in every cell because of homologous chromosomes. In contrast, non-homologous chromosomes enhance genetic diversity by reshuffling the sequence of genes during meiosis. Therefore, non-homologous chromosomes are crucial to evolution.

Homologous and Non homologous Chromosomes Difference

 Summary:

The genome contains two distinct types of chromosomes: homologous and non-homologous. In the meiotic process, homologous chromosomes pair. Alleles of the same genes located at the same loci on both chromosomes make up the homologous pair. Nonetheless, non-homologous chromosomes comprise alleles from multiple genes. The association of alleles is what differentiates homologous chromosomes from non-homologous ones.