Final answer:
A thymine dimer is a type of DNA damage where two adjacent thymine bases bond covalently due to UV light exposure, leading to potential mutations if unrepaired. DNA repair mechanisms like photoreactivation and nucleotide excision repair correct these dimers to preserve genetic stability.
Step-by-step explanation:
What is a Thymine Dimer?
A thymine dimer is a form of DNA damage that occurs when two adjacent thymine bases in a DNA strand become covalently linked after exposure to ultraviolet (UV) light. This dimerization can cause a distortion in the shape of the DNA molecule, which can interfere with DNA replication and transcription processes. If a thymine dimer is not repaired, it can lead to frameshift or point mutations, as the DNA polymerase may incorrectly replicate the dimerized bases.
Effects of Thymine Dimers on DNA Processing
Thymine dimers, if left unrepaired, can result in a 2-base deletion in one chromosome, affecting genetic information and potentially leading to genetic diseases or cancer. Repair mechanisms include photoreactivation and nucleotide excision repair. Photoreactivation, using the enzyme photolyase and visible light, directly repairs the dimer but is not present in placental mammals such as humans. Nucleotide excision repair involves the removal of the damaged segment of DNA and its replacement with correctly paired nucleotides, maintaining the integrity of the genetic information.