Quiz 3

• DNA Sequencing


  The process of reading DNA fragments so as to determine the exact sequence of base pairs in a sample of DNA
• Human Genome Project


  • 13 year project aimed at sequencing the entire human genome
  • Several scientists from around the world worked on the project
  • Completed in 2003
  • 3 billion base pairs were sequenced
• Why was the Human Genome Project done?

  • Scientists thought that if we could know the entire sequence of the human genome we could determine and cure disorders that affect the human population
  • Our DNA could be compared to other organisms
• 99.9% of ALL human DNA is identical
• There are approximately 35000 genes in the human population. Much less than the expected 100,000
• Risks of the Human Genome Project

  • Privacy - All of the genome is known, so your DNA is not so "unique" anymore
  • Financial - If genetic disorders can be determined to exist in the population, can insurance etc, be denied?
  • Ethical - Should we be playing God?
• Benefits of the Human Genome Project

  • Knowledge of predisposition to disease - We know about the predisposition to disease so treatments and/or preventions can be implemented
  • Analysis of diseases - Diseases that are known can be analyzed and preventions/cures created
• Genetic Engineering


  The manipulation of an organism's genetic material to modify the proteins it produces
• How does genetic engineering operate?

  1. Restriction Enzymes

  2. Recombinant DNA

  3. DNA Amplification

  4. Gel Electrophoresis

  5. CRISPR

  6. DNA microarray
• Restriction Enzymes


  • Originally discovered as a bacterial defense mechanism, used by bacteria to cut up invading viral DNA and thus restrict viral growth in the bacterial cell
  • These enzymes, also known as Restriction Endonucleases can be used by scientists to "CUT" DNA into short fragments
  • Each fragment of DNA has "Sticky Ends" (short segments of unpaired nucleotides on each end of a fragment), that can then be inserted into other lengths of DNA
• Recombinant DNA


  A new segment of DNA made by combining or joining DNA from two different sources
• DNA Amplification


  • The process of generating a large sample of DNA from a single gene or DNA fragment
  • Creating a large sample of DNA is useful if a scientist needs to sequence a sample of DNA, or use it for making recombinant DNA or to run on gel electrophoresis (crime scene investigation)
  • Two methods are used: Cloning Vectors and Polymerase Chain Reaction (PCR)
• Cloning Vectors


  • The use of a bacteria or virus to produce many copies of a foreign DNA sequence
  • Foreign DNA is spliced into the DNA of either a virus or bacteria (i.e. recombinant DNA) and they are then allowed to reproduce
  • The DNA is then harvested from the bacteria or virus at a later time
• Polymerase Chain Reaction (PCR)


  • An automated method of reproducing DNA by using enzymes such as DNA polymerase and primers
  • DNA section is placed in a solution of free nucleotides
  • Heated to open up the double helix
  • DNA polymerase is added and DNA replication occurs
  • Cycle is repeated several times
  • End result is lots of DNA sequence that was wanted
• Gel Electrophoresis


  • Fragments of DNA are separated according to their mass and electrical charge
  • On one end of a gel plate a sample of DNA fragments is placed
  • The gel is given an electric current causing it to become polarized on the other end
  • The fragments are negatively charged and they are attracted to the other end of the gel
  • The fragments move according to their mass, with the smaller fragments moving more quickly toward the opposite end of the gel
  • After a while a characteristic pattern of bands emerges, known as the DNA FINGERPRINT of a person
• CRISPR


  • A technology that can be used to edit genes
  • CRISPR finds a specific bit of DNA inside a cell
  • The Cas9 protein can easily be programmed to find and bind to almost any desired target sequence by giving it a piece of RNA to guide it in its search
  • The DNA is then cut and repaired with an introduced mutation that disables the faulty gene or repairs it
• DNA microarray


  • A tool for analyzing gene expression levels using cDNA (copy DNA) probes
  • The microarray is a chip (usually a glass or polymer membrane) that contains thousands of little holes (cells)
  • Each cell contains a nucleic acid sequence that can bind with a mRNA sequence
  • mRNA is extracted from the cell or cells to be studied, used to create cDNA, which is then marked with a fluorescent tag
  • The tagged cDNA is then incubated with the microarray and the cDNA binds with the specific sequences found in the cells
  • When incubation is finished, the microarray is scanned and analyzed to compare patterns of gene expression in each cell sample
• Genetically Modified Organism (GMO)


  Organisms where genes are turned on or off
• Genetically Modified Food (GMF)


  Foods where genes are turned on or off
• Transgenic organism


  Genetically engineered products that have foreign DNA inserted into its genome, approved for agricultural use in North America
• Examples of GMF's/GMO's (Transgenic products)


  • Herbicide resistant corn
  • Cows with high milk production or containing human proteins
  • Rice with greater amounts of Vitamin A and Iron (Golden Rice)
  • Transgenic Salmon
  • Insulin producing bacteria
  • PCB eating bacteria
  • Oil eating bacteria
• Risks of GMO's / GMF's

  • More herbicides used
  • If genes spread to wild organisms could affect biodiversity
  • Could create superbugs
• Benefits of GMO's / GMF's

  • Alleviate world hunger
  • Employment for more farmers etc.