Famous+IB+Scientists


 * Davson & Danielli**- Proposed 'Protein sandwich' model of cell membrane based on electron microscopy.
 * Singer & Nicolson**- Improved model of cell membrane...one with embedded proteins - based on evidence from 'freeze fracturing'/'freeze etching'
 * Pasteur**- Used 'swan necked' flasks to disprove theory of 'Spontaneous Generation'.
 * Miller & Urey**- Recreated the conditions of prehistoric Earth in their Lab. Were able to produce organic material from inorganic chemical components.
 * Friedrich Wohler**- Synthesis of urea from inorganic materials. Disproved the theory of 'Vitalism'
 * Watson & Crick**- Used models to determine the structure of DNA. Important as this represents a scientific way of viewing something normally too small to see.
 * Meselson & Stahl**- Allowed bacteria to reproduce using N14 (Nitrogen). They moved the bacteria to a new dish where they had to use the heavier isotope N15. All the DNA in these new bacteria (made by binary fission in this new location, using the heavier N15) was slightly heavier than the original DNA. They could centrifuge the DNA and compare the samples from the two locations... they had different weights. By analyzing the change in weights they could see that the DNA in the new daughter cells must contain one full strand from the original parent and one new strand made up with the heavier isotope. DNA replication was therefore semi-conservative. [|Please Watch this Video.]
 * John Cairns**- Invented Cairns' technique. Grew cells in a culture of tritiated thymidine (Thymine+ deoxyribose sugar+ radioactive tritium). Cells placed on membrane to digest their membranes with lysozyme. Photographic paper laid over them- the radioactive elements turned the paper dark... indicating the presence of the DNA strand. In this way DNA strands could be measured. (Discovered that prokaryote DNA is one long circle). [|Video.]
 * Mendel**- Principles of inheritance. Law of segregation and Law of independent assortment. BUT he also pioneered many research methods- including the use of quantitative data and performing lots of repetitions.
 * Darwin**- Natural Selection (based primarily on observation of the beak sizes of finches on different Galapagos islands).
 * William Harvey**- Performed a number of experiments and discovered that blood circulated around the body. Proposed the existence of capillaries even though there was no way at that time to see them. He went arrow d Europe with his demonstrations and overcame a lot of opposition from scientists who wouldn't let go of previous beliefs.
 * Florey and Chain**- Designed a method to purify penicillin and tested it on mice and then humans. Relatively limited testing performed when compared to the trials that modern drugs must go though- previous disastrous examples would be thalidomide- a drug that was found to relieve morning sickness. It was prescribed to patients after generally inadequate levels of testing. It was later found to produce serious birth defects.
 * William Harvey**- Investigation of sexual reproduction in deer. Disproved the previous 'seed and soil' theory that had been proposed by Aristotle.

They repeated the experiment with viruses containing radioactive DNA. The resultant offspring did carry some traces of radioactive material. Thus they demonstrated that DNA is the material of inheritance. [|Video.]
 * __Higher Level__**
 * Herschey & Chase**- Knew that chromosomes were made of protein and DNA. So which was the material that determined inheritance? Used viruses with radioactive protein coats to see if their 'offspring' (from an infected cell) would carry the radioactive material. They did not.


 * Rosalind Franklin**- Used X-ray crystallography (diffracting X-rays with crystals of a material to determine the molecular structure of the material) to determine the double helix structure of DNA. She did not publish her findings as she wanted to double check her work. Her research partner, Maurice Wilkins, showed her images to James Watson (Watson and Crick) and they were able to determine the complete DNA structure and published before her.


 * Sanger**- Used (colored) di-deoxyribonucleic acid 'tags' to identify the sequence of bases in any strand of DNA. Termed the 'Chain termination' method or 'Sanger sequencing'. Yes ... we did see it. [|Video.]


 * Calvin**- Used the 'lollipop apparatus' (a glass jar that looked like an upside down lollipop) to determine the sequence of organic compounds produced in photosynthesis. Introduced radioactive hydrogen carbonate into a broth of photosynthetic algae. Let them photosynthesise for a few minutes and then killed the cells and examined them for radioactive compounds. So... After X minutes there is compound 1; Repeated experiment but left it a little longer before killing and looking for radioactive compounds... so- after Y minutes there is compound 2; By repeating this experiment over and over... extending the time given- he could eventually produce the sequence of the compounds that are produced in photosynthesis and work out what was happening at each stage ... thus producing the Calvin cycle. [|Video.]


 * Morgan**- Discovered sex linkage. Mendel's monohybrid crosses could predict the probable ratios of inherited characteristics. But there were discrepancies- some organisms (fruit flies called drosophila) did not follow the predicted patterns. Morgan determined that some characteristics (genes) must be associated with a sex chromosome and are therefore inherited together always. [|Video].**Bateman, Saunders and Punnett** would later go on to identify 'Crossing Over' as another reason why Mendelian ratios were not always accurate as this process would create what they called ...'recombinants'.


 * Jenner**- Vaccination


 * Landsteiner**- ABO blood system and the Rhesus system.