International Baccalaureate Biology Option B Introduction Biotechnology and Bioinformatics Welcome to the International Baccalaureate Revision Guide for Option B. Sections B1 to B3 form the common core and sections B4 and B5 are the Additional Higher Level sections. The format is the same as the Core Guides with key points, simple diagrams and large numbers of Grey Box Questions and Self-test quizzes. Pale blue boxes contain information that helps with understanding by providing additional information. However you do not need to learn this. Other coloured boxes, such as these green and yellow ones, contain information that you do need to know. The Option is tested, along with experimental skills and techniques linked to the Core material, in Paper 3. I would greatly value any feedback on this Revision Guide. Please feel free to email me at Oxford Study Courses osc@osc-ib.com. Ashby Merson-Davies
2 IB Option B Ashby Merson-Davies
B2 Biotechnology in Agriculture B2 Biotechnology in Agriculture Transgenic Organisms Key points Guide SL page 35, HL page 37). A transgenic organism has had one or more genes An example is Saccharomyces cerevisiae on page from one or more different species inserted into its 7. The genes for the malate transporter protein and genome. (See page 13). the malate degrading enzyme came from two Bioinformatics (see page 18 ) plays a role in different organisms. identifying genes, called target genes, that may be suitable candidates for transferring. The inserted genes will be translated into the same protein as in the original organism because the genetic code is universal. Transgenic organisms will therefore produce proteins that were not previously part of their Additional sequences have to be inserted along with the gene to form the DNA construct. These could include: A promoter sequence. A terminator sequence. A marker or recognition gene. A signal sequence to determine whether free ribosomes or ribosomes on the rer are used. (see core guide SL page 45, HL page 55). An antibiotic resistance gene. Overcoming Environmental Resistance in Crops Key points Environmental resistance means any biotic or abiotic factor in the environment that reduces crop yield such as: Competition from weeds, Lack of water, Attack by pests such as viruses, bacteria, fungi, arthropods. Example 1 glyphosate tolerant soybean (GT soybean) Glyphosate is a biodegradable general herbicide. It kills plants by inhibiting the enzyme required for the synthesis of three essential amino acids. Researchers found a soil bacterium with the same enzyme but which is not inhibited by glyphosate. This gene was transferred to soybean using the tumour inducing plasmid (Ti plasmid) in the bacterium Agrobacterium tumefaciens. (See Core Guide SL page 172, HL page 249 and also the Box on the next page for details of this process). Soybean seeds are sown and after the crop has started to grow, along with the weeds, it is sprayed with glyphosate. The weeds are killed and by the time the glyphosate has been biodegraded in the soil and further weed seeds start to germinate the soybean will out-compete them for light. 2.1 Soy bean pods. IB Option B Ashby Merson-Davies 13
B2 Biotechnology in Agriculture b. Microinjection Microinjection is using a very fine needle to inject DNA directly into the plant cell nucleus. natural repair mechanism. The plant tissue is held in place by suction and the needle moved by a micromanipulator while being observed through a microscope. An advantage with this method is that the cell is not damaged. suction plant cell syringe needle 2.4 A micromanipulator being used to inject an egg cell that can be seen on the monitor. c. Biolistics Biolistics is using a gene gun to fire metal particles, usually gold, coated in the gene directly into a leaf. compressed air plastic disc with DNAcoated gold particles leaf screen When a shot of compressed air is fired the plastic disc is driven against the screen and the gold particles are ejected at high speed into the leaf cells. The tip of the barrel of a gene gun this is the black part in the photo on the right. 2.5 A gene gun in use. Marker Genes Key points It is important to know if gene transfer has been successful. A marker gene is often inserted along with the target gene. Marker genes include: antibiotic resistance genes. (See the yellow box on page 14 [Ti plasmid]) fluorescent protein genes. One widely used is green fluorescent protein (GFP) which came from a jellyfish. A more recent one is dsred from a coral. 2.6 This San Diego beach scene has been drawn on an agar plate with bacteria expressing 8 different colours of fluorescent proteins derived from GFP and dsred. IB Option B Ashby Merson-Davies 21
B4 Medicine 44 IB Option B Ashby Merson-Davies