What happens when your DNA is damaged? - Monica Menesini
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This animation demonstrates how, during DNA replication, mistakes can occur as DNA polymerase copies the two strands. The wrong nucleotide can be incorporated into one of the strands causing a mismatch. Normally there should be an "A" opposite a "T" and "G" opposite a "C". If a "G" is mistakenly paired with a "T", this is a potential mutation. Fortunately, cells have repair mechanisms.
Likewise, too much sunlight can damage DNA; a chemical reaction produces thymine dimers distorting DNA.
The main inner source of DNA damage are ROS (reactive oxygen species), also known as free radicals, produced by cell metabolism. The amount of free radicals has been linked to aging -- tortoises live longer because they have a very low metabolic rate.
The same mechanism that repairs double strand DNA breaks (homologous recombination) is also involved in crossing over during meiosis, the process that increases genetic variability and drives evolution.
Several human genetic diseases are known or suspected to be due to repair defects. These defects often lead to an increased incidence of cancer. For example Xeroderma pigmentosum is due to a mutation in a gene whose product is involved in nucleotide excision repair. People suffering from this disorder are extremely prone to UV-induced skin cancers as a result of exposure to sunlight. Read about this and other diseases due to repair defects.
If you want to know more about DNA damage and repair, you can subscribe for this free online course by MIT.
Scientists think that accumulation of DNA damage and a decrease in the body's ability to fix itself may be an important component of aging. Find out more information about the biology of aging.
In 2015, the Nobel Prize in Chemistry was awarded to Tomas Lindahl, Paul Modrich and Aziz Sancar for having mapped, at a molecular level, how cells repair damaged DNA and safeguard the genetic information. Read more about their research here.
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