Discovery of degenerate genetic code (question) - (Feb/13/2022 )

Hello to all,

I am a student in Master1 of cellular and molecular biology. While looking for how the genetic code was discovered (and especially the notion of degeneracy), I came across a historical article from 1961 (General Nature of Genetic Code for Proteins, Crick et al.). I am trying to understand how the T4 rII system used in the experimental model in the article works. I found a good video in English explaining this but I am not sure I understand the difference between K and B cultures very well. Could someone please enlighten me? Here is the link to the video: https://youtu.be/4PwprU2KYoM

Have a nice day,

Jérome (from France). 

Welcome to the site.

In this case the K12 and B cultures are strains of Escherichia coli that have different genetic characteristics that means that the bacteriophages being used to infect the E. coli display different phenotypes.

You can find out a little bit about them on the (English) Wikipedia page on E. coli in molecular biology (B is directly below the linked K12), and a more complete description of the genotypes on the Openwetware E. coli wiki. There are tons of strains on that one - I would go with BL21(or BL21(DE3)) for B and MG1655 for the K12 wild-type.

Pedigrees of K12 strains: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC408331/

Delbruck description of B strain: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC374122/