Cells have evolved various repair mechanisms to deal with mutational changes in DNA in order to ensure that accurate replication occurs. What is the enzymatic system that removes dimers and inserts new pyrimidine molecules in their place?
1) SOS system
2) Repair system
3) Mutation system
4) Replication system

The enzymatic system that removes dimers and inserts new pyrimidine molecules in their place is the Repair system. This system is responsible for repairing damaged DNA and maintaining its integrity.

One example of a repair mechanism is nucleotide excision repair (NER). NER is a highly conserved pathway that removes a wide range of DNA lesions, including dimers. Dimers are formed when two adjacent pyrimidine bases, such as thymine or cytosine, become covalently linked due to exposure to UV radiation. This can lead to distortions in the DNA helix and hinder accurate replication.

In NER, a group of proteins, including the excision repair cross-complementing group 1 (ERCC1) and group 2 (ERCC2), recognize the damaged site and initiate the repair process. The damaged DNA strand is excised, and new nucleotides are inserted by DNA polymerases to fill the gap. Finally, the repaired DNA is ligated to restore the integrity of the double helix.

So, the Repair system plays a crucial role in maintaining DNA fidelity by removing and replacing damaged nucleotides, such as dimers, to ensure accurate replication.