What is a gene?

A gene is the elementary functional physical unit of hereditary. Genes, which are comprised of DNA, act as directives in the construction of protein molecules. In the human body, genes differ wildly in size, ranging between several hundred DNAs and over two million bases. The Human Genome Project, a collaborative international research project, approximates that a typical adult human have anywhere from 20,000 to 25,000 genes. It is worth noting that every human possess two copies of every gene, with each set inherited from the mother and father.

More than 99% of genes in humans are identical. The remaining genes, amounting less than 1% of the total, are the ones responsible for the unique features of every individual, such as blood type and hair colour.

Molecular Properties and Structure of Genes

The traditional molecular representation of a gene as a globule or bead on a DNA sequence (or string), as we tend to see in images or on plastic models (typically in double helix form), are no longer accepted by the scientific community. Advances in modern sciences, particularly in biochemistry, medicine and naturally, genetics, have presented us with a much clearer picture of genes (though there is still some debate on the subject).

Simply put, every cell in our body contains 46 different strands of DNA (Deoxyribonucleic acid). Each of these strands is comprised of millions of particles, and the particles are called nucleotides. There are four variants of nucleotides, which are labelled as A, C, T and G. All of these are part of a gene. More accurately though, a gene is a stretch of DNA containing specific sequences of A, C, T and G nucleotides which contain hereditary protein construction directives.


A gene by any other name…

However, sometimes genes are not called genes – they are called by the specific element or function it has, such as coding sequence, genomic locus and transcribed region. There is actually a loud minority within the scientific community which advocates limiting the use of the term gene to indicate a relationship between genomic sequences and phenotypic traits.

In addition, as we have mentioned above, most genes have repetitive nucleotides pattern and can be identified. As such, many common genes have actually been named. Some of the more well-known ones include,

  • GABRG3(found on chromosome 15) - increases the risk of alcohol dependence
  • FUT2 (a Golgi stack membrane protein) - increases the risk of ear infection in Filipinos and South Asians
  • Huntingtin(HTT, on chromosome 4) – a reliable indicator of adult-onset Huntington's disease