Biotechnology. Biotechnology is the
use of biological organisms and processes to produce commercially valuable
products. Many of the earliest biotech
products made use of bacteria to produce recombinant proteins. That is, the bacteria produced human proteins
that could be used as therapeutics in humans.
This feat is possible because both humans and bacteria shared a common
ancestor. Remarkably, the genetic
information that human cells use to make proteins can be used by bacteria found
in human feces.
Sometimes, the use of bacteria and yeast in the production
of foods such as cheese and beer is placed under the umbrella of
biotechnology. However, for our purposes
in this class, biotechnology will be limited to the products created using
modified genetic information. For
example, the recombinant proteins mentioned above are the result of taking
genetic information from human cells and, through the use of numerous molecular
biology processes, bringing that information into bacterial cells in the
context that these organisms can understand.
Central Dogma of Biology. Despite the need to go back in time a couple billion years, humans and bacteria share a common ancestor. Evolutionary theory as well as the central dogma of biology weave together to allow bacteria to read genetic information derived from human cell to make human proteins. The central dogma of molecular biology posits that genetic information flows from DNA to RNA to protein. While the “DNA to RNA” step can be reversed, the same is not true for genetic information flowing from the form of protein back to nucleic acids such as DNA and RNA.
Last Universal Common Ancestor. Of all known living organisms, DNA serves not only as the information that is both passed down from one generation of organisms to the next but also as the source code for proteins using RNA as an intermediate, or messenger, molecule. This fact implies that the last universal common ancestor (aka LUCA) had a DNA genome. All organisms since have made use of DNA genomes as well as the genetic code used to decipher the information. With DNA genomes in all living organisms and a shared used of a genetic code, biotechnology is built on the ability of scientists to use molecular biology tools to edit and modify DNA. The possible modifications are nearly endless.
Model organisms. The
extent of biodiversity makes it impractical to study all organisms in a
laboratory setting. Instead, representative
organisms from the tree of life have been disproportionately studied. Multiple factors have guided the selection of
these “model organisms” including the ease of culturing asexual organisms and
breeding sexual organisms. Biological
principles that are determined in model organisms are usually applicable to
non-model organisms because of both the central dogma of biology and the
concept of LUCA.
In a positive feedback loop, research of a model organisms
incentivizes additional research of that model organism because tools to study
the organism are developed in one study that could be used in follow-up studies
of that organism. However, recent improvements
in molecular biology and biotechnology methods are reducing the barriers of
entry for studying new organisms and, thus, reducing our reliance on any
particular model organism.
Many questions were inspired by this CRISPR review.
- PAM stands for “protospacer adjacent motif”. What does this mean?
- Compare CRISPRi and CRISPRa. Which Cas9 variant would be useful for these approaches? What Cas9 fusion protein would you create for CRISPRi? CRISPRa?
- How would you set up your CRISPR-based experiment to preferentially use NHEJ DNA repair pathway? What type of mutation would you expect?
- How would you set up your CRISPR-based experiment to preferentially use HR DNA repair pathway? What kind of mutation could you expect?
- Why would you likely use two gRNAs in Cas9n- and RFN-based experiments? What does it mean that this would reduce your chances of causing off-target effects?
- The ribozyme-gRNA-ribozyme method of creating a sgRNA sounds complex. Why wouldn’t you just clone sgRNA sequence alone in a normal PolII-based promoter? How can this RGR system produce sgRNAs in a tissue-specific manner?
- Discuss the similarity between processing the CRISPR array in bacteria and processing polycistronic tRNA-gRNA (PTG) sequences.
- CRISPR systems are adaptive immune systems in bacteria and archaea that provide resistance to bacteriophage. How has this been adapted to plants? How has this been adapted to animals?
- Compare GMOs and GEs. Why might the latter be more acceptable?
- How do gene drives work?
Biotechnology Chapter 9 Day 3 Questions
- How does the yeast two-hybrid system work?
- Examine figures 6 and 7 from this paper. Draw each panel and explain the experimental design as well as the interpretation of the co-immunoprecipitation data.
- Experiments are designed to answer questions that researchers have. What type of questions would be answered using an antigen capture immunoassay? A direct immunoassay array?
- In experiments using protein interaction arrays, what types of molecules could “bind to” the spotted proteins?
- Discuss the analogy that networks of metabolites can be compared to city streets.
Biotechnology Chapter 9 Day 2 Questions
- If you were to kick a soccer ball as hard as you could, how many seconds would it likely take for it to travel 10 feet? If you were to kick a bowling ball as hard as you could, how many seconds would it likely take for it to travel 10 feet? How is this analogy similar to a mass spectrometer that uses a TOF detector?
- The average amino acid has a mass of 0.11 kilodaltons. What would be the maximum length of a protein that could be detected using MALDI according to the book’s description of an upper limit for this instrument? What would be the maximum length you could use if ESI was used? Would either of these be OK to use for most full-length human proteins?
- In ESI, the ions can “dry off” quickly. How is this accomplished?
- Why is ESI, but not MALDI, compatible with HPLC? If you cut out a protein “spot” from a 2D-DIGE, could you use MALDI to analyze your sample?
- Compare how 2D-DIGE and 2D-liquid chromatography successfully separate a complex mix of proteins.
- If a protein is digested by a protease after each histidine, could you look at a primary protein sequence and determine the size that each peptide fragment that you would expect? Could a computer do this analysis for all the proteins in the human “proteome”? (Hint: The answer is yes for both.) Do you think there are databases online that you can query with your mass spec results? (The point here is that mass spec data may look complex, but a computer has no problem with this kind of data.)
- Why would peptides with the sequences “Glu-His-Arg-Gly” and “His-Arg-Gly-Glu” be considered ambiguous? How could tandem mass spectroscopy (ms/ms) be useful in this situation?
- Why is it OK to mix protein lysates from two samples in the SILAC method? How can differences between the expression levels of protein X be estimated in this procedure?
- Cloned genes can be expressed as “tagged” proteins. What kind of column would you use to purify “His6”-tagged proteins? How about FLAG-tagged proteins? Strep-tagged proteins? GST-tagged proteins? MBP-tagged proteins? How do you get each the tagged protein type to be “released” from the columns?
- Compare introns and inteins.
- Antibodies are “binding proteins” that are specific for an “epitope”. After studying figure 9.21, describe how phage display could be used to determine the epitope of a monoclonal antibody.