Gene activity or gene expression = the set of processes by which information from a gene is used to create a functional product, often a protein. The major steps in the gene expression include:
1) Transcription: the sequence of nucleotides that form a gene, organized into a double helix of DNA, are used to create a single strand of RNA, formed by nucleotides too.
2) Splicing: cut and merge of RNA pieces. In complex organisms, the newly formed molecule of RNA includes both coding and non-coding regions (respectively exons and introns – link to a future post), therefore introns need to be removed while exons are joint together to form a final messenger RNA (mRNA).
3) Translation: the conversion of a mRNA sequence into a chain of aminoacids which forms a protein. Three RNA nucleotides (a codon) code for a single aminoacid, therefore a protein of 30 aminoacids can be built from a mRNA of 90 nucleotides.
Both transcription and translation are common to all known form of life and together they are referred to as the central dogma of molecular biology.