Direct DNA damage

Direct DNA Damage

Direct DNA damage occurs when DNA directly absorbs a harmful agent. This damage can cause changes in the structure of the DNA molecule, leading to mutations and potentially leading to diseases such as cancer.

Types of Direct DNA Damage

There are several types of direct DNA damage, including:

• Single-strand breaks: These occur when one of the two strands of the DNA molecule is broken.
• Double-strand breaks: These occur when both strands of the DNA molecule are broken. This is a more severe form of damage and is more difficult for the cell to repair.
• Base modifications: These occur when the chemical structure of the bases in the DNA molecule is altered. This can lead to incorrect base pairing during DNA replication.
• Crosslinks: These occur when covalent bonds form between bases on opposite strands of the DNA molecule, preventing the strands from separating and interfering with DNA replication and transcription.

Causes of Direct DNA Damage

Direct DNA damage can be caused by a variety of factors, including:

• Ultraviolet radiation: This can cause the formation of pyrimidine dimers, which are a type of base modification.
• Ionizing radiation: This can cause single- and double-strand breaks and base modifications.
• Chemical mutagens: These can cause base modifications and crosslinks.

Repair of Direct DNA Damage

Cells have several mechanisms for repairing direct DNA damage, including:

• Nucleotide excision repair: This is used to repair pyrimidine dimers and other base modifications.
• Base excision repair: This is used to repair small, non-helix-distorting base modifications.
• Mismatch repair: This is used to repair errors in base pairing that occur during DNA replication.
• Non-homologous end joining and homologous recombination: These are used to repair double-strand breaks.

See Also

• Indirect DNA damage
• DNA repair
• Mutagen
• Carcinogen

Direct DNA damage Resources
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