The Science

Why use E. coli​ ?

  • E. coli is a model organism
  • Most strains of E. coli are non-toxic
  • It has helped us understand gram-negative bacteria
  • It has helped us learn important molecular biology concepts
  • It is easy to work with
  • ​It is cheap to use
Answer the following questions after watching the video:
  1. What are the 3 postulates of the Modern Cell Theory?
  2. What are the 2 prokaryotic kingdoms?
  3. What are the 4 eukaryotic kingdoms?
  4. What are 3 similarities between prokaryotic and eukaryotic cells?
  5. What are 2 differences between prokaryotic and eukaryotic cells?
  6. What is the function of ribosomes?

Prokaryotes vs Eukaryotes

  • E. coli is a prokaryotic cell, while human cells are eukaryotic
    • This makes using E. coli to produce human proteins more challenging, but luckily not impossible
    • Understanding the difference between both cell types allows researchers to manipulate E. coli to undergo human (eukaryotic) cell processes

Protein Synthesis

The following video reviews the key steps in the process of protein synthesis:
Answer the following questions after watching the video:
Transcription
  1. Where does it occur?
  2. What happens in this process?
  3. What enzyme is involved in this process?
  4. What are the complementary base pairs of DNA?
  5. When mRNA is made from a strand of DNA, what is the mRNA base complement to adenine on the DNA? Why?










​Translation
  1. Where does it occur?
  2. What 2 parts make up ribosomes?
  3. What are the 3-base codes in mRNA called?
  4. What is the purpose of tRNA?
  5. What is found on the two ends of tRNA?
  6. What is the start codon?  What amino acid does it code for?
  7. What kind of bond links amino acids together?
  8. When does protein synthesis stop? Why?

Post-Translational Modifications

Before a human protein (polypeptide) can become active, it may need to undergo modification.  The following video classifies these modifications into ones that are co-translational or post-translational.  These modifications may be structural or may alter the activity or function of the protein.  

​Since human proteins are more complex than the ones normally produced by E. coli, it is difficult and sometimes impossible to create active human proteins in E. coli.  The post-translational modifications that are needed by most human proteins are ones that E. coli cannot do naturally.  Scientists are working on changing the post-translational abilities of E. coli.
​Answer the following questions after watching the video:
  1. What are the 2 categories of protein modifications?
  2. The video focuses on the category that most protein modifications fall under.  Which category is it?
  3. What is glycosylation and what type of proteins does it happen to? What is glycosylation important for? Provide an example.
  4. What is lipidation and what type of proteins does it happen to?  Provide an example.
  5. ​What is phosphorylation?  Provide an example.
  6. What is methylation?  Provide an example.
  7. What is proteolysis?  Provide an example.
  8. What is ubiquitination?​

DNA Cloning, Recombinant DNA and Transformation

The following video reviews the concepts of DNA cloning, recombinant DNA and transformation.  The process of transformation changes ('transforms') bacteria so that it expresses a new trait.  Using transformation, E. coli can be manipulated to express a new trait and produce a human therapeutic protein. 
​Answer the following questions after watching the video:
  1. ​What is DNA cloning?
  2. What do we use to cut a gene of interest out of DNA?
  3. What is a plasmid?
  4. What does DNA ligase do?
  5. What does heat shock help bacteria do?
  6. Why is it useful to add an antibiotic resistance gene to a recombinant plasmid?
  7. What is the name of the process that uses the steps described in this video to create multiple copies of a gene of interest in bacteria?