Biotechnology Dolly and surrogate Mom Genetically modified rice.
Fourteen month-old genetically engineered (“biotech”) salmon (left) and standard salmon (right). Biotechnology Biotechnology, defined broadly, is the engineering of organisms for useful purposes. Often, biotechnology involves the creation of hybrid genes and their introduction into organisms in which some or all of the gene is not normally present.
Gene cloning for pharmaceutical production DNA fingerprinting Biotechnology We’ll examine:
Recombinant DNA, Gene Cloning, and Pharmaceutical Production These are mature and widely utilized biotechnologies. DNA can be cut at specific sequences using restriction enzymes. This creates DNA fragments useful for gene cloning.
The enzyme EcoRI cutting DNA at its recognition sequence Restriction Enzymes are Enzymes That Cut DNA Only at Particular Sequences Restriction enzyme animation Different restriction enzymes have different recognition sequences. This makes it possible to create a wide variety of different gene fragments.
DNAs Cut by a Restriction Enzyme Can be Joined Together in New Ways These are recombinant DNAs and they often are made of DNAs from different organisms.
Plasmids are Used to Replicate a Recombinant DNA Plasmids are small circles of DNA found in bacteria. Plasmids replicate independently of the bacterial chromosome. Pieces of foreign DNA can be added within a plasmid to create a recombinant plasmid. Replication often produces 50-100 copies of a recombinant plasmid in each cell.
Harnessing the Power of Recombinant DNA Technology – Human Insulin Production by Bacteria
Human Insulin Production by Bacteria and cut with a restriction enzyme 6) join the plasmid and human fragment
Human Insulin Production by Bacteria Mix the recombinant plasmid with bacteria. Screening bacterial cells to learn which contain the human insulin gene is the hard part.
Route to the Production by Bacteria of Human Insulin One cell with the recombinant plasmid A fermentor used to grow recombinant bacteria. This is the step when gene cloning takes place. The single recombinant plasmid replicates within a cell. Then the single cell with many recombinant plasmids produces trillions of like cells with recombinant plasmid – and the human insulin gene.
Route to the Production by Bacteria of Human Insulin The final steps are to collect the bacteria, break open the cells, and purify the insulin protein expressed from the recombinant human insulin gene.
Route to the Production by Bacteria of Human Insulin Overview of gene cloning. Cloning animation
Reverse transcription: cDNA Cloning Suppose we need to clone a gene containing lots of introns. What will happen when the bacterium tries to express it? To overcome this problem, we can start with mRNA isolated from tissues that produce the desired protein. We then use reverse transcriptase enzyme (produced by a retrovirus related to HIV) to reverse transcribe the mRNA into a DNA molecule that now is free of introns. Now we can ligate "sticky ends" onto the cDNA and recombine it into a phage or plasmid vector. Or: Use Proteins sequence - BLAST website to get DNA sequence and PCR to make multiple copies of cDNA that can then be cloned.
DNA, the Law, and Many Other Applications – The Technology of DNA Fingerprinting A DNA fingerprint used in a murder case. The defendant stated that the blood on his clothing was his. What are we looking at? How was it produced?
DNA Fingerprinting Basics Different individuals carry different alleles. Most alleles useful for DNA fingerprinting differ on the basis of the number of repetitive DNA sequences they contain.
DNA Fingerprinting Basics If DNA is cut with a restriction enzyme that recognizes sites on either side of the region that varies, DNA fragments of different sizes will be produced. A DNA fingerprint is made by analyzing the sizes of DNA fragments produced from a number of different sites in the genome that vary in length. The more common the length variation at a particular site and the greater the number the sites analyzed, the more informative the fingerprint.
A Site With Three Alleles Useful for DNA Fingerprinting DNA fragments of different size will be produced by a restriction enzyme that cuts at the points shown by the arrows.
The DNA Fragments Are Separated on the Basis of Size The technique is gel electrophoresis. The pattern of DNA bands is compared between each sample loaded on the gel. Gel electrophoresis animation
Possible Patterns for a Single “Gene” With Three Alleles In a standard DNA fingerprint, about a dozen sites are analyzed, with each site having many possible alleles.
A DNA Fingerprint When many genes are analyzed, each with many different alleles, the chance that two patterns match by coincidence is vanishingly small. Cloning animation Cloning animation Cloning animation Cloning animation Cloning animation DNA detective animation HGP fingerprinting page
SLT 3/8/05 DNA and the Law Some applications of DNA fingerprinting in the justice system.
Genetically Modified Foods Many of our crops in the US are genetically modified. Should they be?
GM Crops are Here Today Source: Pew Initiative on Food and Biotechnology, August 2004.
Methods for Plant Genetic Engineering are Well-Developed and Similar to Those for Animals
Golden rice (yellow) with standard rice (white). Golden Rice is Modified to be Provide a Dietary Source of Vitamin A Worldwide, 7% of children suffer vitamin A deficiency, many of them living in regions in which rice is a staple of the diet.
Genetically Modified Crops Genetically Modified Cotton (contains a bacterial gene for pest resistance) Standard Cotton
Current Concerns by Scientists Focus on Environmental, Not Health, Effects of GM Crops The jury’s still out on the magnitude of GM crop’s ecological impact, but the question is debated seriously.
Current Concerns by Scientists Focus on Environmental, Not Health, Effects of GM Crops