Monthly Archives: September 2017

Genetically Modified Organisms

Our last Area of Study in Unit 4 Biology is: 

“How do Humans impact on biological processes?”

Key knowledge: 

DNA manipulation:
• the use of enzymes including endonucleases (restriction enzymes), ligases and polymerases
• amplification of DNA using the polymerase chain reaction
• the use of gel electrophoresis in sorting DNA fragments, including interpretation of gel runs
• the use of recombinant plasmids as vectors to transform bacterial cells.

Biological knowledge and society:
• techniques that apply DNA knowledge (specifically gene cloning, genetic screening and DNA profiling) including social and ethical implications and issues
• the distinction between genetically modified and transgenic organisms, their use in agriculture to increase crop productivity and to provide resistance to insect predation and/or disease, and the biological, social and ethical implications that are raised by their use
• strategies that deal with the emergence of new diseases in a globally connected world, including the distinction between epidemics and pandemics, the use of scientific knowledge to identify the pathogen, and the types of treatments
• the concept of rational drug design in terms of the complementary nature (shape and charge) of small molecules that are designed to bind tightly to target biomolecules (limited to enzymes) resulting in the enzyme’s inhibition and giving rise to a consequential therapeutic benefit, illustrated by the Australian development of the antiviral drug Relenza as a neuraminidase inhibitor
• the use of chemical agents against pathogens including the distinction between antibiotics and antiviral drugs with reference to their mode of action and biological effectiveness.

Genetically modified organisms – 

Insect resistant (‘Bt’) cotton

Insect resistant (‘Bt’) corn

Herbicide tolerant (‘Roundup ready’) canola

Iron-fortified wheat

Golden rice

Drought-tolerant wheat

‘Round up’ resistant soy beans

Chapter 13 – DNA tools and techniques

Image source

Genetic tools (Restriction enzymes, ligases and DNA probes and primers): These tools are used as genetic scissors (restriction enzymes), genetic glue (ligases – to stick DNA fragments together) and genetic markers (probes that recognise and attach to specific sequences of DNA with a fluorescent or radioactive marker) Gene Technology video (1 of 6)  (YouTube, 9.05min)

DNA amplification: Using a Polymerase Chain Reaction (PCR) researchers can create many copies of DNA in a test tube. Access the Image Source link for a self-paced Virtual Laboratory activity that demonstrates the process of PCR using animations. Gene Technology video (2 of 6)  (YouTube, 9.54min)

Gel Electrophoresis: This technique is used to separate fragments of DNA according to their size – longer fragments with a large number of base pairs travel more slowly through the substrate (agarose gel), while shorter fragments with a smaller number of base pairs travel a greater distance. A buffer solution is added to the apparatus and DNA fragments are ‘cut’ at specific sites using restriction enzymes and loaded, together with a fluorescent dye, in ‘wells’ at the negative end of the apparatus.  An electric charge is applied and the negatively charged DNA fragments are attracted to the positive end of the gel matrix. Gel Electrophoresis on YouTube. and Gene technology (3 of 6) (YouTube, 9.41min)

DNA recombination: Scientists are able to insert fragments of DNA from one organism into another organism, bringing together genetic material from various sources. Recombinant DNA produces genetically modified organisms, that may add desirable characteristics to food crops, for example

DNA sequencing: DNA sequencing is the process of determining the precise order of nucleotides within a DNA molecule. DNA Sequencing on YouTube.  and Gene technology (4 of 6) (YouTube, 9.59min) and Gene Technology (5 of 6) (YouTube, 6.53)

DNA profiling: Also called DNA fingerprinting, this technique compares DNA from victims, suspects and crime scenes to determine which samples have the most in common. How does DNA fingerprinting work from the Naked Science Scrapbook (YouTube). 

Gene cloning: Molecular cloning is a set of experimental methods in molecular biology that are used to assemble recombinant DNA molecules and to direct their replication within host organisms. Gene cloning in plain English on YouTube. 

Genetic screening: Used to identify  genetic disorders or potential risk of disease. For example, when a family has a history of females suffering from breast cancer, a genetic screening test can identify the presence or absence of a particular gene that indicates susceptibility to this cancer. Pro-active treatment may include removal of the breasts to prevent the disease. 

Genetically Modified Organisms (GMO) and transgenic organisms: When genetic engineering is used to insert specific sequences of DNA into host organisms.

Gene transformation: “In molecular biology, transformation is the genetic alteration of a cell resulting from the direct uptake, incorporation and expression of exogenous genetic material (exogenous DNA) from its surrounding and taken up through the cell membrane.” Bacterial transformation by zabaaz on YouTube.

Hominoids, hominids and homonins – what’s the difference?

 

Image source

Primates: (Order Primate) includes all species with prehensile (grasping digits) with opposable thumbs. They also have forward facing eyes with binocular vision, a well-developed cerebral cortex and bicuspid teeth. This includes all the new world monkeys (such as spider monkeys) and old world monkeys (macaques), as well as the Greater and Lesser apes.

Hominoids: refers to the broad term for great and lesser apes which includes gibbons, orangutans, gorillas, chimpanzees and humans. They have no tail, an upright gait and arms shorter than their legs.

Hominids: includes just the great apes, orangutans, gorillas, chimpanzees and humans

Hominins: Refers to the bipedal human species and their relatives.  such as the following:

  • Sahelanthropus tchadensis (Tournai) – mix of human and chimp features, small brain, may have been bipedal (6.5 mya)
  • Ardipithecus ramidus – Primitive teeth, probably bipedal (4.5mya)
  • Australopithecus afarensis (Lucy) – Walked upright, about 1.2m – 1.4m tall , basic stone tools (3.5mya)
  • Homo habilis (Handy man) – More advanced stone tool making and use, brain size half of modern humans (2 mya)
  • Homo ergaster – Small face and teeth, advanced tool use and may have used fire (2.5mya)
  • Homo erectus (Java man) – Modern features, but with a visible brow ridge, brain size 60-70% of modern humans (1 mya)
  • Homo heidelbergensis – Found in Europe, brain size very similar to modern humans, advanced tool use (1 mya)
  • Homo neanderthalensis – Stocky, adapted to cold, tool use, social structures, rudimentary language possible, brain size slightly larger than modern humans. (500, 000 ya)
  • Homo floresiensis (the hobbit) is known from fossils discovered in Indonesia and co-existed with Homo sapiens. (17,000 – 95,000 ya)
  • Homo sapiens (including the sub-species Denisovans) (present day)

The Australian Museum has some good information about how the definitions for these terms have changed over time, causing lots of confusion for students and scientists alike. New technologies, such as CT scans and DNA analysis, have given us new evidence to support different theories of human evolution than from fossil morphology alone.

The Science of Human Evolution (YouTube, 54.42min) is an interesting video that describes the features of various human ancestors, based on their fossil remains.

Evolution from Ape to Man (YouTube, 50.43min) is another video that describes how the search for the “missing link” in human evolution was based on flawed thinking and how scientists have changed their theories depending on the evidence that becomes available.

Human face evolution in the last 600 million years (YouTube, 1.07min) shows an animated progression of facial features from our distant ancestors to the modern human face we recognize today.

Great Human Odyssey (YouTube, 1hr 52.06min) describes how human ancestors migrated out of Africa and developed skills, technology and talent to survive in almost every environment across the globe.

Modern humans may have interbred with Neanderthals and Denisovans (YouTube, 10.54min) – an excellent segment from Catalyst on ABC with the evidence that modern humans have DNA in common with neanderthals and Denisovans indicating that modern humans may have interbred with these species.