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Techniques

Using dbSNP and ClinVar to Classify Gene Variants

As we discussed previously, the gaps in our understanding of the human genome make variant classification an extremely difficult job. However, with each passing day our knowledge increases, and the tools to help us become increasingly more efficient. Let’s pick up where we left off in our first article about variants. After checking Ensemble to…

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A Crash Course in BLAST Searching

Simple BLAST searching is pretty straightforward to many of us. Just plug in your sequence, select the species genome, and hit search! But have you ever wondered what it takes to run a BLAST query using these mammoth-sized (no pun intended!) sequence databases? BLAST searching can produce dozens, hundreds, or even thousands of candidate alignments.…

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How to Use Ensembl to Classify Gene Variants

Even though our knowledge about genomes grows daily, and in huge leaps, we sometimes need to remind ourselves that DNA was first isolated in 1869 and its molecular structure was only identified in 1953. The PCR reaction only hit the scientific community as recently as 1983! So even though we are growing fast, we are…

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A Beginner’s Guide to Exosome Isolation

For all of you who have never heard of exosomes: You are missing out on a whole new paradigm in cell-to-cell communication. Exosomes are tiny extracellular vesicles that arise from fusion of the plasma membrane with specific endosomal compartments called multivesicular bodies. Most cells types make exosomes, and release them in order to communicate with…

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Modeling – in the World of Proteins

Computational protein structure prediction provides three-dimensional structures of proteins that are predicted by in-silico techniques. Such protein modeling relies on principles from known protein structures obtained via x-Ray crystallography, NMR Spectroscopy, as well as from physical energy functions.  There are three main methods of modeling: The first and favorite method is Homology Modeling,1-2 Followed by the…

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The Amazing World of Biofilms

What do water pipe slime, dental plaque, and persistent contact lens case contamination have in common? All are the result of biofilms! Biofilms are aggregates of microbes that adhere to surfaces using secreted matrices. Although relatively under explored, this fascinating phenomenon plays a critical role in some of the biggest challenges currently facing medicine, ranging…

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Color Transmission Electron Microscopy

There are two types of electron microscopy—transmission electron microscopy (TEM) and scanning electron microscopy (SEM). SEM creates fascinating 2D images by bouncing electrons off the surface of the sample. I highly recommend searching for SEM samples on Google images. While SEM images are aesthetically amazing, the TEM images bring us inside the world of the…

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The qRT-rtPCR Control You Should Be Doing, But Probably Aren’t

Every man, woman, and dog is doing quantitative real time reverse transcriptase PCR (qRT-rtPCR) these days. It’s a great method to measure your favorite transcript’s expression levels. One of the big plusses (like the Swiss flag!) of quantitative PCR in general is its high sensitivity. In principle, it can detect and quantify one molecule of…

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Why Isn’t My Culture Growing? The S-Curve Explained

Whether you work with human cell lines or microbes, their growth is governed by the same principles. I invite you to learn about something that lies at the base of any work with cell culture — whether cells have circular or linear chromosomes—the S-curve of the population growth. The length of each phase depends on…

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Quantifying Allele-Specific Gene Expression Using PCR-Based Methods

Allele-specific expression can occur for various biological reasons, such as gene imprinting, or differential transcription caused by mutations, or single nucleotide polymorphisms (SNPs), or epigenetic alterations. Traditional end-point RT-PCR or qRT-PCR-based methods only detect overall levels of mRNA expression from a given gene rather than mRNA transcripts originating from individuals. If your project requires more…

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Five Things That Irritate Flow Cytometrists

I have worked in flow cytometry for a number of years. I’m still annoyed that many myths and imprecisions are perpetrated and perpetuated. Here is my non-exhaustive list of cytometry-related beliefs that send flow cytometrists screaming from the room or at least, being English, make me tut sadly. Forward Scatter Equals Cell Size No No…

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Guide to Making and Storing Competent Yeast Cells

Yeasts, such as Saccharomyces cerevisiae, Schizosaccharomyces pombe and Pichia pastoris, are routinely used in biology research labs around the world. Yeasts are easy-to-culture, unicellular eukaryotes, and make excellent model organisms because of the similarity of their genes and proteins with those of their mammalian counterparts. Yeast cells are used to study gene function, protein interactions,…

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From Cells to Scope: Chamber Slide Immunochemistry

Immunolabeling is the tried-and-true immunochemistry method of getting the stain you want onto the molecular target you want. Whether that target is contained within a large region of tissue (immunohistochemistry) or inside a single cell (immunocytochemistry), the ability to accurately label large numbers of samples will simplify your workflow and help you to achieve excellent…

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Bacterial Transformation Troubleshooting for Beginners

The first time I did a transformation was when I worked with site directed mutagenesis. I cloned a protein sequence into the p15TVL vector, created my mutants (but that’s another story), and was finally ready for the next step: transformation and expression of my desired protein. Little did I know that my enthusiasm would fall…

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An Introduction to In-Gel Zymography

Enzymes are special among proteins. It is not enough to detect them. You need to know their activity level. If you have devoted a substantial part of your research to studying proteases, like I did, you’ll know how crucial it is to choose an appropriate enzyme assay. There’s a heap of lab techniques out there…

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What’s in Your Cell Culture Medium?

Anyone who has performed mammalian cell culture will recognize the typical media recipe: 1 bottle of DMEM, 10% serum, a few other magical ingredients, throw it together and put it on your cells to keep them alive and happy. However, do you know what each ingredient does? Let’s look at the common ingredients in cell…

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