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A similar genetic code is used by most organisms on Earth, but different organisms have different preferences for the codons they use to encode specific amino acids. This is possible because there are 4 bases (A, T, C, and G) and 3 positions in each codon. There are therefore 64 possible codons but only 20 amino acids and 3 stop codons to encode leaving 41 codons unaccounted for. The result is redundancy; multiple codons encode single amino acids. Evolutionary constraints have molded which codons are used preferentially in which organisms - organisms have codon usage bias.

Can you imagine how much space a million plasmids would fill? Two weeks ago, Addgene edged passed our one million plasmids shared milestone by ending the day with 1,000,002 plasmids shipped. Reaching one million plasmids shared might have you wondering how many plasmids leave Addgene headquarters every day. That would be an average of 673 plasmids each day. This requires tremendous coordination amongst the lab team, shipping team, and others to ensure that everything will ship out in time - from assembling the boxes, to inoculating tubes, and to packing and shipping. Every single day.

This guest post was contributed by Johnny Kung, Director of New Initiatives for the Personal Genetics Education Project (pgEd).

Advances in genetic technologies and other biomedical innovations promise an improved understanding of how our bodies work, new treatments for debilitating diseases, and maybe even ways to alleviate health disparities. But as the science moves forward at a blistering pace, it is becoming ever more urgent for scientists to engage broadly with diverse communities, to raise awareness about where science is and where it is going, and to thoughtfully address the hopes and concerns of these communities. This kind of engagement and two-way dialogue is crucial if we as a society are to figure out the best way to shepherd technologies through thorny ethical issues, ensure that everyone will have the possibility of benefiting from the fruits of scientific research, and prevent technological advances from exacerbating existing inequalities and injustices.

Every few months we highlight a subset of the new plasmids in the repository through our hot plasmids articles. These articles provide brief summaries of recent plasmid deposits and we hope they'll make it easier for you to find and use the plasmids you need. If you'd ever like to write about a recent plasmid deposit please sign up here.

Genome-wide CRISPR/Cas9 screens are a high-throughput systematic approach for identifying genes involved in a biological process. These screens provide an alternative to genome-wide RNAi screens, which although highly effective, are affected by low on-target efficacy, non-specific toxicity, and off-target effects. The flaws of RNAi screens are well characterized and strategies exist to control for these faults. However, it’s still unclear if similar pitfalls exist for CRISPR screens and how best to design these screens to controls for flaws. Recently the Bassik Lab at Stanford developed a new genome-wide CRISPR knockout screen to analyze the following unanswered questions about CRISPR screen design.