MadSci Network: Cell Biology
Query:

Re: What is the purpose of adding Salmon Sperm DNA for Yeast Transformation?

Date: Tue Apr 17 07:31:05 2012
Posted By: Billy Carver, Grad student, Biomedical Sciences, Vanderbilt University
Area of science: Cell Biology
ID: 1332606626.Cb
Message:

Hello Felicia,

Thanks for the great question!

As a former yeast biologist, I have transformed yeast dozens of times without really giving a lot of thought to the role that carrier DNA plays. In my lab, we used calf thymus DNA in lieu of salmon sperm DNA, but their purpose is roughly equivalent. Simply stated, scientists use carrier DNA because it increases transformation efficiencies by 10- to 100-fold. There are two prevailing theories as to for how this happens:

  1. There are a multitude of nucleases in the yeast cell, and by adding DNA bulk, the plasmid of interest is more likely to make it to the nucleus without being degraded.
  2. The yeast cell wall, because of its chemical composition, binds DNA; adding more extraneous DNA allows the wall to bind that DNA, allowing some of the plasmid to make it into the yeast cell.
Unfortunately, this is as much information as I was able to find about the purpose of carrier DNA. I hope this answers your question!

Sources:
Burgers, PMJ and Percival LJ. Transformation of yeast spheroplasts without cell fusion. Analytical Biochemistry. 163. 391-397. 1987.
http://www.ncbi.nlm.nih.gov/pubmed/3310730

Gietz RD, Schiestl RH, Willems AR, and Woods RA. Studies on the transformation of intact yeast cells by the LiAc/SS-DNA/PEG procedure. Yeast. 11. 355-360. 1995.
http://www.ncbi.nlm.nih.gov/pubmed/7785336


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