A gene is a physical structure made from DNA. Genes function primarily by being expressed in the form of proteins. The conversion from gene to protein is a multistage process. First the gene is transcribed, making a RNA copy of itself that is then translated to create a protein.
1. Transcription
           Most of a cell's DNA is located in the nucleus in the form of chromosomes. When a gene is expressed it generates a copy of itself in the form of messenger RNA (mRNA). RNA differs from DNA in three characteristics: 1) RNA is single stranded; 2) the base uracil replaces thymine; 3) the sugar is ribose rather then deoxyribose; and 4) RNA is unstable and often is degraded within several hours of its creation.
           Initially, the mRNA contains both the coding regions of the gene (exons) and the intervening, non-coding sequences (introns). Through a process called splicing, the introns are removed and the exons are joined together to form the template for protein synthesis. Once spliced, the mRNA template leaves the nucleus and goes into the cytoplasm where protein synthesis occurs.

 Splicing removes the introns from the mRNA and joins together the gene exons. The spliced mRNA serves as the template for protein synthesis.
2. Translation

           The building blocks for both DNA and RNA are nucleotides. The building blocks for proteins are amino acids. Translation refers to the conversions of the genetic sequence into the protein sequence.
           The actual translation of the genetic code to protein code is done by transfer RNA (tRNA). One end of the tRNA recognizes the genetic code in mRNA, while the other end recognizes and binds the corresponding amino acid. Three consecutive nucleotides, called a codon, encode for one amino acid (See Genetic Code).
           Protein synthesis occurs in the cytoplasm on structures called ribosomes. A protein is a chain of amino acids bound together. The order of amino acids is determined by the genetic code in the template mRNA. Amino acids are brought to the ribosome bound to tRNA. The specific tRNA binds to the template mRNA and the amino acid is transferred from the tRNA to the growing protein chain. This process is repeated until a stop codon is reached, then the completed protein is released from the ribosome. Proteins have numerous functions, from acting as structural components to acting as catalyts in cellular reactions.
Genes are transcribed in the nucleus, creating a mRNA copy of the gene. The mRNA is spliced and then goes to the cytoplasm where it serves as a template for protein synthesis on ribosomes.