Mutation (Medical Entrance)

Wolf-Hirschhorn syndrome is a characteristic phenotype resulting from a partial deletion of chromosomal material of the short arm of chromosome 4 (4p deletion).

5BU induces transition mutation in DNA. When a nucleotide containing 5-bromouracil is incorporated into the DNA, it is most likely to pair with adenine. However, it can spontaneously shift into another isomer which pairs with a different nucleobase, guanine. If this happens during DNA replication, a guanine will be inserted as the opposite base analog. This results in a change in one base pair of DNA, specifically a transition mutation.

Aneuploidy occurs when nondisjunction at a single chromosome results in an abnormal number of chromosomes.

Ectopic recombination involves unequal crossing over. In ectopic recombination, crossing over occurs between non-homologous chromosomes during meiosis. Duplication occurs at the site of exchange.

Becker muscular dystrophy is caused by mutation in the dystrophin gene. It is characterised by slow progression of muscle weakness in legs and pelvis.

hCONDEL deletions might be responsible for the evolutionary differences present among closely related species. Such deletions in humans are referred to as hCONDELs. They may be responsible for the anatomical and behavioral differences between humans, chimpanzees and other mammals.

Amplification or duplications of oncogenes are a common cause of many types of cancer. In such cases, the genetic duplication occurs in somatic cells and affects only the genome of cancer cells.

Deletion of a small piece of chromosome 22 causes DiGeorge syndrome.

A fusion gene is a hybrid gene formed from two previously separate genes. It can occur as a result of translocation, interstitial deletion and chromosomal inversion.

Neurofibromatosis type (NF-II) is caused by mutations of the merlin gene. The main manifestation of the disease is the development of symmetric, non-malignant brain tumors in the region of the cranial nerve VIII, which is the auditory-vestibular nerve that transmits sensory information from the inner ear to the brain.

UV light can induce adjacent pyrimidine bases in a DNA strand to become covalently joined as a pyrimidine dimer.

Psoralens are natural compounds (furocoumarins) present in plants. They form DNA cross links to induce mutation. The crosslinking reaction by psoralens targets TA sequences intercalating in DNA and linking one base of the DNA with the one below it.

Transposable elements usually cause insertions. TEs jump into a gene and produce a mutation.

Chromosomal inversions can be seen in heterozygous condition of polytene chromosomes. Small inversions in most species remain undetected. Polytene chromosomes are exploited for observing inversions.

The proposed cause of length changes in satellite mutation is replication slippage. It is caused by mismatches between DNA strands while being replicated during meiosis. Replication slippage can produce duplication of short genetic sequences.