Eukaryotic organisms have two primary cell types --- germ and somatic. Mutations can occur in either cell type. If a gene is altered in a germ cell, the mutation is termed a germinal mutation. Because germ cells give rise to gametes, some gamete s will carry the mutation and it will be passed on to the next generation when the individual successfully mates. Typically germinal mutations are not expressed in the individual containing the mutation. The only instance in which it would be expressed is if it negatively (or positively) affected gamete production. Somatic cells give rise to all non-germline tissues. Mutations in somatic cells are called somatic mutations. Because they do not occur in cells that give rise to gametes, the mutation is not passed along to the next generation by sexual means. To maintain this mutation, the individual containing the mutation must be cloned. They"re several different types of gene mutations. Point mutations are the most common type of mutation. A single point mutation, also called a base substitution, occurs when a single nucleotide is replaced with a different nucleotide. A point mutation results in a base pair substitution after replication and possibly a mutant protein after transcription and translation. Another type of mutation is a frameshift a mutation which is caused by the insertion or a deletion of a base pair. An inserted or deleted nucleotide alters the triplet grouping of nucleotides into codons and shifts the reading frame so that all nucleotides downstream from the mutation will be improperly grouped. The result is a protein with extensive missense ending sooner or later in nonsense. .
Mutations that occur at the chromosome level resulting in changes in the gene distribution to gametes during meiosis are chromosomal mutations, which are caused when parts of chromosome break off or rejoin. Chromosomal mutations involve chromosome sets, whole chromosomes, and chromosome segments.