HP1 (heterochromatin protein 1) is one of the most important Su(var) proteins. The HP1 chromodomain binds to histone H3 that is trimethylated at lysine 9 (H3K9me3).

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Transcriptionally active genes are preferentially repaired via transcription-coupled repair.

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Global genome repair and transcription-coupled repair differ in their mechanisms of damage recognition (XPC vs. RNA polymerase II).

TLS Online TPP Program

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#Unit 3. Fundamental Processes

transitions, which are pyrimidine-to-pyrimidine and purine-to-purine substitutions, such as T to C and A to G;

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#Unit 3. Fundamental Processes

transversions, which are pyrimidine-to-purine and purine-to-pyrimidine substitutions, such as T to G or A and A to C or T.

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#Unit 3. Fundamental Processes

Mutations that alter a single nucleotide are called point mutations.

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#Unit 3. Fundamental Processes

Chemical mutagens can be divided into two groups:

those that are mutagenic to both replicating and nonreplicating DNA, such as the alkylating agents and nitrous acid; and 

those that are mutagenic only to replicating DNA, such as base analogs— purines and pyrimidines with structures similar to the normal bases in DNA.