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Plasmids 101: What is a plasmid?

Posted by Margo R. Monroe on Apr 2, 2020 2:17:39 PM

Originally published Jan. 14, 2014.

Any newcomer who joins a molecular biology lab will undoubtedly be asked to design, modify, or construct a plasmid. A plasmid is a small circular piece of DNA found in bacterial cells, and someone new to plasmids may need some extra guidance to understand the specific components that make up a plasmid and why each is important.

Our “Plasmids 101” series designed to educate all levels of scientists and plasmid lovers - serves as an introduction to plasmids. Plasmids 101 will provide you with an overview of general molecular biology knowledge and techniques, and empower you with a firm understanding of the fundamentals. Our mission is to curate a one-stop reference guide for plasmids, so that you can spend less time researching the basics and spend more time developing cleverly designed experiments and innovative solutions necessary for advancing the field.


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Topics: Plasmids 101, Plasmids

Plasmids 101: Plasmid Incompatibility

Posted by Leah Schwiesow on Mar 31, 2020 9:15:00 AM

Plasmid incompatibility is defined as the inability of different plasmids to be maintained in one bacterial cell. In this Plasmids 101 post, we’ll cover why this happens, how it might affect your work, and how understanding it can be used for good. 

First, why are plasmids incompatible? Plasmid incompatibility occurs when multiple plasmids within one cell have the same replicon and/or partitioning system. Let’s start with the replicon- the part of the plasmid that contains the origin of replication and the replication control machinery (Need a refresher on the Origin of Replication? See our Plasmids 101: Origin of Replication blog). 

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Topics: Plasmids 101, Plasmids

Plasmids 101: Positive and Negative Selection for Plasmid Cloning

Posted by Jennifer Tsang on Aug 22, 2019 8:43:39 AM

You’ve worked hard to purify your gene of interest, get it into your plasmid backbone, and zap the mixture of DNA into cells. Unfortunately, not every cell successfully takes up plasmid DNA. Among those that do, some now have plasmids that contain your gene of interest, but others will uptake plasmid backbones that re-ligated back on themselves.

Therefore, your cloning strategy needs to identify cells containing the plasmid construct you’re seeking. Fortunately, there are many ways to do this involving positive selection, negative selection, and/or screening. We’re focusing on positive and negative selection in this blog post, but don’t worry, we’ll cover screens in a future post.

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Topics: Plasmids 101, Plasmid Cloning, Plasmids

Plasmids 101: Transformation, Transduction, Bacterial Conjugation, and Transfection

Posted by Alyssa Cecchetelli on Jun 25, 2019 8:54:52 AM

Horizontal gene transfer (HGT) is the movement of genetic material between organisms. It plays a key role in bacterial evolution and is the primary mechanism by which bacteria have gained antibiotic resistance and virulence. Scientists have studied how HGT occurs in nature and have learned how to introduce genetic materials into cells in the lab.

The introduction of foreign DNA or RNA into bacteria or eukaryotic cells is a common technique in molecular biology and scientific research. There are multiple ways foreign DNA can be introduced into cells including transformation, transduction, conjugation, and transfection. Transformation, transduction, and conjugation occur in nature as forms of HGT, but transfection is unique to the lab. Let’s take a look at these different methods of DNA insertion.

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Topics: Plasmids 101, Plasmids

Plasmids 101: Biotinylation

Posted by Alyssa Cecchetelli on Nov 15, 2018 8:50:12 AM

Biotin and its binding partner avidin are commonly used today in molecular biology for an array of different techniques and protocols. In this post we will discuss the natural role of biotin, biotinylation, the discovery of the biotin-avidin interaction and the uses of biotinylation in molecular biology!

Learn about in vivo biotinylation of bacterial fusion proteins

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Topics: Plasmids 101, Plasmids

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