gene mutation and molecular medicine

Point mutations

Mutations that result from the gain, loss, or substitution of a single nucleotide.

Transitions

Base pair substitutions where a purine base is converted to the other purine and its matching pyrimidine is converted to the other pyrimidine.

Transversions

Base pair substitutions where a purine base is converted to a pyrimidine and its matching pyrimidine is converted to a purine.

Silent mutation

A change in a gene's sequence that has no effect on the amino acid sequence of a protein.

Missense mutation

A change in a gene's sequence that changes the amino acid at that site in the encoded protein.

Nonsense mutation

A mutation that results in a change from sense codon to a stop (nonsense) codon, causing the amino acid sequence to end early.

Loss-of-stop mutation

A mutation that results in a change from a stop (nonsense) codon to a sense codon, causing additional amino acids to be added to the end of the protein.

Frame-shift mutation

The addition or deletion of a single or two adjacent nucleotides in a gene's sequence, resulting in the misreading of mRNA during translation and the production of a nonfunctional protein.

Chromosomal rearrangement

Large changes in the sequence of DNA caused by breakage and rejoining of DNA molecules, including deletions, duplications, inversions, and translocations.

Deletion

A mutation resulting from the loss of a continuous segment of a gene or chromosome.

Duplication

A mutation in which a segment of a chromosome is duplicated, often by the attachment of a segment lost from its homolog.

Inversion

A rare 180-degree reversal of DNA sequence within a segment of a gene or chromosome.

Translocation

A rare mutational event that moves a portion of a chromosome to a new location, generally on a non-homologous chromosome.

Mutagen

Any agent that increases the mutation rate.

Short tandem repeats (STRs)

Short, moderately repetitive sequences of DNA used for DNA fingerprinting.

DNA fingerprinting

The identification of individuals based on their unique pattern of allele sequences, commonly short tandem repeats and single nucleotide polymorphisms.

Gene therapy

Treatment of a genetic disease by providing patients with cells containing functioning alleles of the genes that are nonfunctional in their bodies.

Genetic screening

A technique for identifying genes involved in a biological process of interest.

Restriction enzyme

An enzyme that cleaves double-stranded DNA at specific sites, used in recombinant DNA technology.

Multifactorial

Referring to the interaction of many genes and proteins with one or more factors in the environment.