Gene expression: The process by which a gene's coded information is converted into the structures present and operating in the cell. Expressed genes include those that are transcribed into mRNA and then translated into protein and those that are transcribed into RNA but not translated into protein (e.g., transfer and ribosomal RNAs).

Gene family - Group of closely related genes that make similar products.

Gene product - The biochemical material, either RNA or protein, resulting from expression of a gene. The amount of gene product is used to measure how active a gene is; abnormal amounts can be correlated with disease causing alleles.

Genetic code - The sequence of nucleotides, coded in triplets (codons) along the mRNA, that determines the sequence of amino acids in protein synthesis. The DNA sequence of a gene can be used to predict the mRNA sequence, and the genetic code can in turn be used to predict the amino acid sequence.

Genetics - Science of heredity

Genome - The entire collection of chromosomes in each cell of an organism

Genomics - A branch of biology dedicated to the development and application of more effective mapping , sequencing  and computational tools.

Genome project - Research and technology development effort aimed at mapping and sequencing some or all of the genome of human beings and other organisms.

Genotype - The actual alleles present in the individual (the gene type)

GTP - (Guanosine triphosphate) An energy-rich nucleotide analogous to ATP that is composed of guanine, ribose, and three phosphate groups and is necessary for peptide-bond formation during protein synthesis.
 
Guanine (G) - A nitrogenous base found both in DNA and RNA. Guanine base-pairs with Cytosine