Dna Repair And Skin Cancer

Sometimes, the errors that occur during DNA replication are not fixed by DNA repair enzymes. These unrepaired errors can lead to mutations. Cancer can occur if the mutations happen within genes that control cell growth and cell division. Scientists hope that by studying DNA replication and DNA repair, they can develop treatments or even cure various types of cancers.

Ultraviolet Light and Skin Cancer

Ultraviolet light, the most energetic part of sunlight, is the

Ultraviolet Light and Skin Cancer

Ultraviolet light, the most energetic part of sunlight, is the

It is important to guard against skin cancer. For example, apply sunscreen before prolonged exposure to sunlight.

main cause of mutations that trigger skin cancer. Skin cancer is the most common type of cancer in the United States. Each year, about 1 million Americans get skin cancer.

When UV light reaches the DNA inside a skin cell, thymine bases that are next to each other on the same strand of DNA can become linked by a covalent bond, as shown in the figure below. Linked thymine pairs are called thymine dimers. Thymine dimers are usually detected by enzymes moving along the DNA strand because the dimers cause a kink in the DNA, as shown in the figure below. Dimers that are not repaired during DNA replication can cause mutations in genes that control cell division. The mutation can trigger a skin cell to become cancerous.

DNA Repair Enzymes and Skin Cancer Treatments

Some organisms do not get skin cancer. One reason is that these organisms have a DNA repair enzyme called photolyase

Thymine dimer

Unrepaired DNA damage can prevent accurate copying of the DNA and can lead to mutations. One example of DNA damage is covalent cross-linking between two thymine bases, which is called a thymine dimer.

(FOH-toh-LIE-AYS). Photolyase is activated by light and can repair thymine dimers caused by UV radiation. Human skin cells can correct UV-induced dimers by a complex process known as excision repair that involves other enzymes. But photolyase uses a more direct and effective mechanism for DNA repair than excision repair. Scientists have already developed a sunscreen containing photolyase to repair the UV-induced DNA damage that occurs when a person is sunburned.

Some researchers want to try to use gene therapy to insert the gene for photolyase in people that are at high risk for skin cancer. Gene therapy is a technique in which a defective gene is replaced with a normal version of the gene. Ongoing studies of DNA repair enzymes may help develop gene therapy and other types of cancer treatments in humans.

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