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Which of the following is not true of DNA repair?
DNA repair can, and does, occur during replication. An easy example of this is the proofreading function of several DNA polymerases. This function is carried out due to the enzymes containing an exonuclease function that allows them to excise incorrect base pairs. p53 is an incredibly important protein that is expressed heavily when DNA damage is detected. It is responsible for activating both DNA repair pathways and apoptotic pathways, preventing the cell from passing replication and cell cycle checkpoints. If the DNA damage is irreparable, the cell may undergo apoptosis.
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Upon double-stranded DNA break, the cell can search the genome for a homologous sequence to serve as a template for repairing the damaged sequence. What is this process known as?
The correct answer is homology directed repair. Using flanking homologous regions upstream and downstream of the double stranded break, the cell is able to determine the precise sequence that is in the damaged region and repair that sequence.
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Which of the following enzymes is responsible for catalyzing the formation of phosphodiester bonds in single- and double-stranded DNA breaks?
DNA ligase catalyzes the formation of phosphodiester bonds between the elements of the DNA backbone. DNA polymerases function in replication of DNA, whereas exonucleases and endonucleases break apart DNA strands by disrupting phosphodiester bonds.
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