Question

ThepicturebelowdepictsthefirstthreestepsofDSB repair homologous recombination with some errors. List the error(s), why each error is a problem, and how this error should (or could) be corrected.

Answer 1

The errors in the first three steps of DSB repair homologous recombination are the absence of MRX and MRN proteins, the absence of phosphorylated Sae2 endonuclease, and the absence of Sgs1 helicase. These errors prevent the proper initiation and execution of the repair process. To correct these errors, MRX and MRN proteins should be present, Sae2 endonuclease should be phosphorylated, and Sgs1 helicase should be present.

Step-by-step explanation:

The errors in the first three steps of DSB repair homologous recombination are:

1. The absence of MRX and MRN proteins at the double-stranded break. These proteins are responsible for recruiting other factors and initiating the repair process.
2. The absence of phosphorylated Sae2 endonuclease. This enzyme is required for cutting the DNA at the break site.
3. The absence of Sgs1 helicase. This enzyme is responsible for unwinding the DNA strands and enabling the repair process.

These errors are problematic because they prevent the proper initiation and execution of the repair process. Without MRX and MRN proteins, other factors will not be recruited, and the repair process will not occur. The absence of phosphorylated Sae2 endonuclease prevents the cleavage of the DNA, which is necessary for the subsequent repair steps. Finally, the absence of Sgs1 helicase impairs the unwinding of DNA necessary for repair.

To correct these errors, the following steps should be taken:

1. Ensure the presence of MRX and MRN proteins at the double-stranded break to initiate repair and recruit other factors.
2. Ensure Sae2 endonuclease is phosphorylated to enable DNA cleavage.
3. Ensure the presence of Sgs1 helicase to unwind the DNA strands for repair.