Genes as Sections of DNA Molecules

A gene is a section of a DNA molecule that controls a particular characteristic in an organism.
Every organism has a set of genes inherited from its parents, which determine its physical and biological traits like eye colour, blood type etc.
Each DNA molecule consists of two strands coiled together in the shape of a double helix.
These strands are made up of nucleotides, which consist of a sugar named deoxyribose, a phosphate group and a nitrogenous base.
There are four types of nitrogenous bases: Adenine (A), Thymine (T), Guanine (G), and Cytosine (C). In DNA, Adenine pairs with Thymine, and Guanine pairs with Cytosine.
The sequence of these bases determines the genetic code, which in turn, designates the type of protein to be produced during protein synthesis.
The length of a DNA strand constitutes multiple genes, and different genes have various base pair lengths.
Genes exist in alternate versions known as alleles, which may lead to variations in inherited characteristics. For example, one allele might code for blue eyes, while another codes for brown.
Mutations, or changes in the DNA sequence, can lead to new alleles. Although these can be harmful, sometimes they may have no effect or can even be beneficial, leading to evolution over generations.
The complete set of genes in an organism comprises its genome.
Genes are copied during cell division, ensuring every new cell receives a complete set of genes.
Errors can occur during DNA replication but there are DNA repair mechanisms to fix most mistakes, ensuring the continuation of life.
Genetic engineering allows scientists to manipulate the genes within an organism. With this technology, they can insert, delete, alter, or move genes within an organism, creating Genetically Modified Organisms (GMOs).
Genetic information is stored in genes as codes - sequences of the nitrogenous bases. This is faithfully replicated and passed on to offspring during reproduction.