Types of DNA Mutations

There are many types of DNA mutations. Some of these mutations occur during DNA replication and others occur due to environmental agents, such as cigarette smoke, sunlight, and radiation. Some mutations are passed onto children and others are not. Those that are passed to children are responsible for hereditary diseases that run in families.

Substitution Mutations

These types of DNA mutations occurs when one base is exchanged for another.. Substitution could cause a small change in a protein that is produced due to a a codon being changed to one in which a different amino acid is encoded. For example, a beta-hemoglobin gene substitution in which a single amino acid in the produced protein is altered, causes sickle cell anemia.

Insertion Mutations

This type of DNA mutation occurs when extra base pairs become inserted into a new and different place in DNA. Tay-Sachs disease is a neurodegenerative disease that is lethal. It is caused by an inserted mutation and is inherited in an autosomal recessive fashion. A deficiency of the lysosomal enzyme beta-hexosaminidase A resulting from insertion is responsible for this genetic condition.

Deletion Mutations

This type of DNA mutation is characterized by a section of DNA being deleted or lost. A variety of diseases can occur due to deletion. These include hereditary neuropathy with pressure palsies (location affected:17p12), Williams-Beuren syndrome (location affected: 17q11.23), and Smith-Magenis syndrome (location affected 17p11.2). Hereditary neuropathy with pressure palsies is a hereditary, progressive, neuromuscular disorder in which the patient is very vulnerable to nerve injury from stretch, pressure, or repetitive use. Williams-Beuren syndrome is a rare genetic disorder in which a patient may experience developmental problems. Smith-Magenis syndrome affects several parts of the body are affected and it is a developmental disorder.

Frameshift Mutations

Frameshift mutations when gene are altered by deletions and insertions resulting in messages no longer being correctly parsed. This type of DNA mutation is believed to play a role in causing Crohn’s disease. Crohn’s disease is a gastrointestinal disorder in which chronic inflammation occurs. This condition is characterized by diarrhea, blood in the stool, weight loss and decreased appetite, abdominal cramping and pain, and ulcers on the intestinal surface. Those who are afflicted with this disorder may also experience fever, arthritis, skin disorders, delayed sexual development or growth (in children), fatigue, eye inflammation, and inflammation of the bile ducts or liver.

Resources

Kansas State University. (1998). Mutation, Mutagens, and DNA Repair. Retrieved on February 28, 2010 from Kansas State University: https://www-personal.ksu.edu/~bethmont/mutdes.html#types

Genetic Health. (2001). Genetics 101: DNA Mutations. Retrieved on February 28, 2010 from Genetic Health: https://www.genetichealth.com/g101_changes_in_dna.shtml

University of California, Berkeley. (2010). Types of Mutations. Retrieved on February 28, 2010 from the University of California, Berkeley: https://evolution.berkeley.edu/evolibrary/article/0_0_0/mutations_03

Image Credits

DNA: clix – sxc.hu