Why does DNA polymerase proofread the new strand?
DNA polymerase proofreads the new DNA strand produced by DNA replication to make sure that any errors are repaired. Errors can lead to cancer in body cells, and genetic disorders in offspring, if errors occur during the production of sperm and egg cells..
The genetic disorder sickle cell anemia is caused by a mutation in which just one nitrogen base in the DNA sequence that codes for the protein hemoglobin is substituted for another.
The genetic disorder cystic fibrosis is caused by the deletion of one single nitrogen base in the DNA sequence that codes for the CFTR gene. CFTR stands for Cystic Fibrosis Transmembrane Conductance Regulator. http://www.nchpeg.org/nutrition/index.php?option=com_content&view=article&id=462&Itemid=564&limitstart=4
So it is essential that there is a mechanism in place that can recognize and repair errors in the replicated DNA.