Chapt 21: DNA Technologies

• A brand of veggie burger has the taste and texture of meat. It includes a protein from soy that is similar to the hemoglobin found in blood. For ease of manufacture, the soy protein is made in yeast cells. The veggie burger that tastes and feels impossibly like a hamburger is the result of biotechnology.
• The BIG Picture: Ancient biotechnologies used selective breeding to give us bakeries and breweries, foods and medicines. Modern biotechnologies manipulate DNA to give us new ways to study, monitor, and treat disease, and alter foods and the environment.
• Heme


  A molecule that is packed into muscle cells of cattle but found in all species, from bacteria to beans to buffalo
• Globin chains


  Differ by species
• Myoglobin


  The protein in the muscles that becomes meat, with a single globin chain
• Hemoglobin


  The protein in blood, with four globins
• Leghemoglobin


  The heme-surrounding protein from soybeans
• Creating a plant-based burger that mimics meat

  1. Inserting the soybean leghemoglobin gene into yeast cells and mass-producing the needed protein

  2. Fermenting the leghemoglobin with "flavor-precursor molecules"

  3. Mixing in wheat and soy protein
• The soybean leghemoglobin made in yeast is identical to the protein in the plants, so the product does not require labeling in the United States as a "genetically modified organism", or GMO.
• Compared to beef, the burger has an 89 percent smaller carbon footprint and uses 87 percent less water and 96 percent less land. It cuts water contamination by 92 percent.
• DNA


  The language of life, the instruction manual for keeping an organism alive
• Biotechnology


  The use or alteration of cells or biological molecules for specific applications, including products and processes
• Genetic engineering/modification


  Any biotechnology that manipulates DNA, including altering the DNA of an organism to suppress or enhance the activities of its own genes, as well as combining the genetic material of different species
• Transgenic organisms


  Multicellular organisms that harbor DNA from other species
• Recombinant DNA


  DNA that combines genetic material from different sources, found in single-celled organisms and in isolated cells growing in culture
• Creating transgenic organisms is possible because all life uses the same genetic code—the same DNA triplets encode the same amino acids.
• Mixing DNA from different species may seem unnatural, but in fact DNA moves and mixes between species in nature-bacteria do it, and it is why we have viral DNA sequences in our chromosomes.
• Human-directed genetic modification is intended to give organisms traits they would not have naturally, such as goats that produce spider silk, tomatoes that grow in salt water, and bacteria that synthesize human insulin.
• Patentable invention


  Must be new, useful, and not obvious to an expert in the field
• Patentable transgenic organisms


  • A corn plant that manufactures a protein naturally found in green beans but not in corn, making the corn more nutritious as a food for people
• Patentable DNA sequences


  • Part of a medical device used to diagnose an inherited or infectious disease
  • DNA-based tests that identify specific mutations or distinguish among bacterial pathogens and identify strains resistant to specific antibiotics
  • DNA used as a research tool
  • Algorithms used to extract information from DNA sequences and databases built of DNA sequences
• The holder of a patent controls how the invention can be used for 20 years following the date of issue.
• In the 1980s, when sequencing a gene was painstakingly slow, only a few genes were patented. In the mid-1990s, with faster sequencing technology and shortcuts to finding the protein-encoding parts of the genome, the U.S. National Institutes of Health and biotech companies began seeking patent protection for thousands of short DNA sequences, even if their functions weren't known.
• Because of the flood of applications, the U.S. Patent and Trademark Office tightened requirements for usefulness and revoked patents on DNA sequences alone. The invention must be useful as a tool for research or as a novel or improved product, such as a diagnostic test or a drug.
• In the United States, more than one in five human genes is patented in some way, and only a few gene patents have been challenged.
• In 2010, a federal judge in the United States ruled that seven patents on the BRCA genes were "improperly granted" because they are based on a "law of nature".


  In 2011, the court invalidated the patents on the two genes, but a federal appeals court overruled that action, claiming that an isolated gene is not the same as a gene in a cell, which is part of a chromosome.
• In 2013 the U.S. Supreme Court ruled that "a naturally occurring DNA segment is a product of nature and not patent eligible merely because it has been isolated".


  The court did allow patenting of complementary DNA (cDNA), which is synthesized in a laboratory using an enzyme (reverse transcriptase) that makes a DNA molecule that is complementary in sequence to a specific mRNA.
• Soon after the controversy over patenting breast cancer genes began to die down, another issue arose: ownership of the gene editing technology CRISPR-Cas9.
• The University of California, Berkeley, published on the CRISPR-Cas9 technique first, but the Broad Institute filed the patent in an expedited program and was granted the initial patent.
• While the two sides were arguing, other researchers filed patents using CRISPR-Cas9 in specific ways, such as creating crops with pesticide resistance, treating genetic diseases, engineering chimeric antigen receptors, and creating induced pluripotent stem cells.
• Recombinant DNA technology


  Adds genes from one type of organism to the genome of another
• Gene cloning


  Making many copies of a specific DNA sequence
• Constructing and selecting recombinant DNA molecules


  1. Requires restriction enzymes, cloning vectors, and recipient cells

  2. Selected DNA is inserted into vectors, and then the loaded vectors are delivered to cells
• Restriction enzymes


  Enzymes that cut DNA at specific sequences
• Cloning vectors


  Pieces of DNA used to deliver specific DNA sequences to cells
• Hundreds of types of restriction enzymes are naturally found in bacteria, where they cut DNA of infecting viruses, protecting the bacteria.
• Some restriction enzymes cut DNA at sequences of four, five, or six bases that are symmetrical in a specific way—the recognized sequence reads the same, from the 5' to 3' direction, on both strands of the DNA.
• Restriction enzyme EcoR1


  • Cuts at GAATTC
• Restriction enzymes cut DNA


  At specific sequences
• Sticky end


  Single-stranded extensions created when restriction enzymes cut DNA, allowing hydrogen bonding between complementary sequences