A gene is a specific sequence of DNA that contains information influencing a characteristic, usually through the production of a functional RNA or polypeptide. A genome is all the genetic information of an organism, including all its genes and non-coding DNA.
This distinction is assessed at both SL and HL in IB Biology, particularly within A3.1 Diversity of organisms.
| Feature | Gene | Genome |
|---|---|---|
| Meaning | A particular DNA base sequence carrying genetic information | The complete genetic information of an organism |
| Scale | A small section of a DNA molecule | All DNA in the organism |
| Function | Can be expressed to produce a functional RNA or polypeptide that affects phenotype | Stores the complete set of information needed for the organism’s development and functioning |
| Example | The gene containing information used to produce insulin | The human genome, including genes, regulatory sequences, introns and other non-coding DNA |
A gene’s information can have an effect through gene expression. A protein-coding gene is transcribed into mRNA, which is then translated into a polypeptide. The polypeptide may function as an enzyme, hormone or structural protein and therefore influence the organism’s phenotype.
The genome is much larger in scope. Members of the same species share most of their genome, but differences such as single-nucleotide polymorphisms create genetic variation among individuals. Genomes also vary greatly in size and base sequence between species; however, a larger genome does not necessarily indicate a more complex organism.
A common misconception is that a genome is simply “all the genes.” This is incomplete: the genome also contains extensive non-coding DNA, some of which regulates gene expression or has other functions.
Exam technique: If asked to “distinguish” between these terms, define both in a directly comparative statement: a gene is one specific DNA sequence, whereas a genome is the organism’s complete genetic information. Avoid describing a chromosome as a genome; a chromosome is one DNA molecule containing many genes and is usually only part of the genome.
