Manipulating Genomes

• DNA sequencing definition


  finding the nucleotide sequence for a gene or a whole genome
• DNA sequencing techniques


  Sanger sequencing, high-throughput sequencing
• Three steps of Sanger sequencing

  create copies of DNA fragments, create complementary strands for each DNA fragment, analyse complementary DNA fragments
• Step 1 Sanger sequencing = create copies of DNA fragments

  extract DNA sample and heat it to break the two DNA strands, cut the strands into DNA fragments, create many copies of the fragments
• Step 2 Sanger sequencing = create complementary strand for each DNA fragment

  place DNA fragments in a mixture containing DNA polymerase, DNA primers, DNA nucleotides and terminating DNA nucleotides, DNA polymerase uses DNA primers to attach to the DNA fragments and then make complementary DNA fragments by using DNA nucleotides. If a DNA polymerase using a terminating DNA nucleotide, no more nucleotides will be added.
• What is the result of terminating DNA nucleotides ?

  many complementary DNA fragments are produced all ending with a different terminating DNA nucleotide
• DNA primer


  A small piece of single-stranded DNA. It acts a signal, binding to and marking the piece of DNA
• terminating DNA nucleotide


  nucleotides that mark the end of a fragment
• DNA polymerase


  An enzyme that catalyzes the formation of the DNA molecule.
• Step 3 Sanger sequencing = analysing complementary DNA fragments


  seperate complementary fragments by length
• From what can we work out the orginal sample of DNA from in sanger sequencing ?

  because we know the terminating nucleotide of each fragment
• features of high-throughput sequencing


  automated, rapid, cheaper than sanger sequencing
• three benefits of DNA sequencing

  enables genome wide comparisons between individuals and species to reveal how closely related they are, predict amino acid sequences of genes to reveal tertiary structure of polypeptides, useful for synthetic biology to develop new drugs
• gel electrophoresis


  a technique used to seperate molecules of DNA, RNA or proteins
• in gel electrophoresis, molecules of DNA and RNA are seperated by...

  mass
• shorter fragments of DNA have a ....

  lower mass
• in gel electrophoresis, proteins are seperated by...

  their mass determined by the size of their R groups or the number of amino acids present OR they can be seperated by charge determined their R group
• How to prepare electrophoresis =

  1. take a piece of agarose gel and cut wells into it

  2. submerse agar gel in buffer solution

  3. load the molecules they want to separate into one of the wells

  4. place a negative electrode at one end of the gel, and a positive electrode at the opposite end

  5. apply an electric current moving from the negative to the positive electrode
• why is a buffer solution used in gel electrophoresis ?

  because it is able to conduct electricity
• how will results show on electrophoresis ?

  the lighter, more negatively charged a molecule is , the faster it will move along the gel and in a given period of time will move further than the ones that are heavier and less negatively charged
• How can multiple samples be compared in electrophoreisis ?

  filling multiple wells in the agar
• How are the different bands in electrophoresis seen ?

  adding a flourescent dye to the gel which glows under UV light
• example of a florescent molecule used in gel electrophoresis

  ethidium bromide
• gel electrophoresis is used to separate DNA fragments for ...

  genome sequencing or DNA profiling
• genetic engineering


  the process of isolating a gene from one organism and placing it into another organism to translate the added gene
• Why can organisms translate added genes ?

  the genetic code is universal
• uses of genetic engineering

  gene therapy, modification of plants, modification of pathogens, pharming
• gene therapy


  when a patients DNA is altered to cure or treat a disease
• two types of gene therapy

  Somatic Gene therapy and germ line gene therapy
• somatic therapy


  a new gene is introduced into somatic cells to target cells in the tissues that need treatment
• feature of somatic therapy

  short lived affect as somatic cells eventually die
• germ-line gene therapy


  the gene is introduced in germ cells meaning that all the cells in the offspring will be altered
• feature of germ-line therapy

  treatment has long term effects that will be inherited
• example of modification of plants through genetic engineering

  modification of soy plants to give them insect resistance
• example of modifying pathogens through genetic engineering


  developing new medical treatments
• pharming genetic engineering


  an animals DNA is altered such that they produce human proteins for medicine or they develop human diseases so that new pharmaceuticals can be tested on them
• Pharming ethical issues


  Should we modify animals to act as models for human diseases ? Should we put human genes into animals
• When a company genetically modifies an organism they will....

  patent this modification
• patent


  prevents other companies from replicating their modification for a limited time period
• why does a patent have a negative impact ?

  the company can charge a large amount of money for a modified organism