What is a cyclobutane pyrimidine dimer?

Cyclobutane pyrimidine dimers are the major lesions produced upon exposure of DNA to UVB light. They arise from a [2+2] cycloaddition of the C5–C6 double bonds of adjacent pyrimidines (Fig. 1).

What happens if pyrimidine dimers are not repaired?

The more you expose your skin to UV light, the more likely you are to get the very unlucky combination of thymine dimers in a cell that are not repaired and lead to cancer in that cell. It can tens of years for such a cell to grow and divide into a cancer tumor you can see, but once it does, it becomes deadly.

What can cause pyrimidine dimers in DNA and what can it impact?

Although UV photons of different energies have various effects on DNA, the most important damage to DNA is the formation of pyrimidine dimers.

How are cyclobutane dimers formed in a polynucleotide?

The formation of cyclobutane-type dimers between adjacent pyrimidine residues in model polynucleotides or DNA may be represented by the general scheme Whereas the formation of all other known photoproducts follows the irreversible path

How are cyclobutane thymine dimers affected by irradiation?

Both the distribution of cyclobutane thymine dimers and the genetic changes caused by irradiation are heterogeneous within cellular DNA. A purely statistical correlation between frequency of dimerization, number of adjacent thymines, and mutation rate is not often observed.

How are 6-4-pyrimidine dimer ( CPD ) formed in DNA?

Furthermore, (non-cyclic) 6-4- pyrimidine-pyrimidone photoproducts (6-4-PP) of the DNA are formed. CPDs and 6-4-PP are formed in a ratio of 10:1, so that the biological significance of CPDs is already numerically predominant.

How are pyrimidine dimers related to UVB damage?

About 75% of this damage can be attributed to the so-called CPD type (CPD= cyclobutane-pyrimidine dimers). This type results from the fact that 2 adjacent pyrimine bases (e.g. thymine bases) form an extremely stable cyclic compound under UVB radiation (cyclobutane-pyrimidine dimers).