Gene

By Mihir Kapse | 2 October 2024

The term ‘gene’ is defined variedly throughout different aspects of biology. It is vaguely defined as there is no particular definition for a gene. The two major definitions widely used are the Mendelian gene and the molecular gene. Mendelian gene is defined as the basic unit of heredity, that is, the passing on of characters from one generation to the next. On the other hand, the molecular gene is defined as a sequence of nucleotides in DNA that is transcribed to produce a functional RNA.

gene

In the 1860s, Gregor Mendel suggested the existence of discrete inheritable units. The term ‘gene’ was introduced by Wilhelm Johannsem in 1909. It originates from the Greek word ‘gonos’ which means offspring and procreation. Our modern understanding of genes has so far come to as ‘a functional unit of DNA’.

In DNA, there are two types of genes:

  1. Coding genes: Genes that contain the instructions to make a protein are called coding genes. These regions are transcribed into messenger RNA by the RNA polymerase, which then gets transported to ribosomes where protein synthesis takes place. This process is called gene expression.
  2. Non-coding genes: Genes that do not code for proteins are called non-coding genes. Instead, they produce functional RNA molecules, like ribosomal RNA and transfer RNA. Some RNAs produced from these genes regulate gene expression, some are essential for RNA splicing, and some play a crucial role in genome stability.

During the process of reproduction, genes carry the traits and other necessary information from the parent to the offspring. These genes make up different DNA sequences, together called a genotype. The genotype of an individual is very specific with respect to the gene pool of the population of a given species. It carries information for everything, hair colour, eye colour, height, skin colour, and whatnot. Genes are the ultimate source of information for the zygote so formed for its growth and development.

Sometimes, during DNA replication, a gene can acquire mutations in its sequence. Subsequently, these cause changes in individuals which can further lead to the evolution of species. Humans share about 98-99% genes with chimpanzees. This merits the fact that humans and chimpanzees have evolved from a common ancestor.

As an interesting fact, for many years, companies were able to patent human genes. Around 20% of the human genome was under patent by 2005. Fortunately, in 2013, the U.S. Supreme Court stopped it.

References:

  1. Orgogozo V, Peluffo AE, Morizot B. The "Mendelian Gene" and the "Molecular Gene": Two Relevant Concepts of Genetic Units. Current Topics in Developmental Biology. 2016
  2. Noble D. "Genes and causation". Philosophical Transactions. Series A, Mathematical, Physical, and Engineering Sciences. 2008
  3. Johannsen W. Elemente der exakten Erblichkeitslehre [Elements of the exact theory of heredity] (in German). Jena, Germany: Gustav Fischer. 1909
  4. Alberts B, Johnson A, Lewis J, Raff M, Roberts K, Walter P. Molecular Biology of the Cell (Fourth ed.). New York: Garland Science. 2002

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