Site Directed Mutagenesis by PCR

Posted by Guest Blogger on Aug 2, 2016 10:30:00 AM

This post was contributed by guest blogger, Kristian Laursen from Cornell University.

Site directed mutagenesis is a highly versatile technique that can be used to introduce specific nucleotide substitutions (or deletions) in a tailored manner. The approach can be used in conventional cloning (to introduce or remove restriction sites), in mapping of regulatory elements (to mutate promoters/enhancers in reporter constructs), in functional analysis of proteins (to perform alanine scanning mutagenesis or targeted substitution of key residues), and in SNP analysis (to introduce naturally occuring SNPs in a plasmid context). The technique is also highly relevant in this age of CRISPR; site-directed mutagenesis generally applies to plasmids, but may also facilitate genome editing. Tailored mutations are commonly introduced to endogeneous DNA through homology-directed repair (HDR) of a CRISPR/Cas9 induced double-stranded break. This site-directed genome editing requires a template of high homology to the endogenous target, yet to facilitate the repair, the template should be resistant to Cas9 cleavage. If a plasmid contains the template, site-directed mutagenesis can be used to mutate the PAM sequence (an NGG sequence critical for Cas9 cleavage), thereby rendering the resulting construct resistant to Cas9 induced cleavage.

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Topics: Lab Tips, Protocols

Gendered Innovations: Why Does Sex of the Cell Matter?

Posted by Guest Blogger on Jul 21, 2016 10:30:00 AM

The post was contributed by guest blogger Londa Schiebinger, PhD, Hinds Professor of History of Science, Stanford University.

Sex and gender are critical components of biological research that are often forgotten or ignored. If we wish to conduct research that fails less and helps more people, we need to take sex into account. Gendered Innovations is an international, collaborative project—funded by the European Commission, the US National Science Foundation, and Stanford University—that harnesses the creative power of sex and gender analysis for innovation and discovery.

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Topics: Lab Tips

Special Delivery: Fluorophore Targeting for FRET Studies

Posted by Guest Blogger on Jul 19, 2016 10:30:00 AM

This post was contributed by guest blogger James D. Fessenden, an Assistant Professor at Brigham and Women’s Hospital.

Biochemists often struggle to understand how a protein of interest actually behaves. How large is it? What parts of it move when you feed it substrate or add an essential cofactor? How many binding partners does it have and how do they come off and on in a cellular environment? If these are pressing issues in your laboratory, then FRET experiments are a viable biophysical path to answers.

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Topics: Lab Tips, Fluorescent Proteins

Plasmids 101: Methylation and Restriction Enzymes

Posted by Marcy Patrick on Jun 30, 2016 10:30:00 AM

Have you ever tried digesting with XbaI or ClaI restriction enzymes and gotten unusual or unexpected results? Or considered why DpnI will degrade your template DNA from a PCR reaction but not the newly synthesized product from a site-directed mutagenesis experiment? The answer to both questions is the same--methylation! Read on to learn about how DNA methylation may affect your restriction digests.

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Topics: Lab Tips, Plasmids 101, Plasmid Cloning

Tips for CRISPR Gene Editing in Mice

Posted by Guest Blogger on Jun 28, 2016 6:59:27 AM

This post was contributed by guest blogger Samantha Young.

The use of CRISPR/Cas9 for gene editing has expanded since its adaptation for use in mammalian cells in 2012-2013. Researchers are now using this system in ever more creative ways, (Wang et al., 2013, Cho et al., 2014). There are several variants of the CRISPR/Cas9 system floating around, and many pre-designed plasmids containing these variants ready for purchase. But what is the easiest and fastest way to use the system in mice? We'll have a post that goes into the mouse genome editing process in a bit more detail in the coming weeks, but, in this post, we will outline a simple method for selecting the guide RNA, validating its efficacy in vitro, and using it in mouse embryos to generate gene modified mouse lines. Hopefully this post will help get your in vivo research up and running as soon as possible!

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Topics: Plasmid Technology, Genome Engineering, Lab Tips, CRISPR

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