All GRE Subject Test: Biology Resources
Example Questions
Example Question #1 : Dna Replication And Repair
Which of the following is not true of DNA repair?
DNA repair cannot occur during replication
p53 is a protein responsible for activating many DNA repair pathways
Irreparable DNA damage may activate pathways that lead to apoptosis
Several DNA polymerases contain an exonuclease function
DNA repair cannot occur during replication
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.
Example Question #2 : Dna Replication And Repair
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?
Crossing over
Directed reversal
Non-homologous end joining
Base excision repair
Homology directed repair
Homology directed repair
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.
Example Question #1 : Understanding Dna Repair
Which of the following enzymes is responsible for catalyzing the formation of phosphodiester bonds in single- and double-stranded DNA breaks?
Exonuclease
DNA polymerase I
DNA polymerase III
Endonuclease
DNA ligase
DNA ligase
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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All GRE Subject Test: Biology Resources
