https://padlet.com/139778/1piwihsgragl9pgp Chapter 10, Honors Bio 1 en-us 2021-02-03 03:02:12 UTC 2025-11-15 22:19:05 UTC hello@padlet.com 139778 https://padlet.com/139778/1piwihsgragl9pgp/wish/1166950769 Rosalind Franklin produced an x-ray image of the DNA structure. It is because of this x-ray image that Watson and Crick could make many of their discoveries about DNA. The x-ray image produced by Franklin shows DNA to be a helix (spiral) with a uniform diameter and the nitrogenous bases located above one another. The thickness of the helix according to the x-ray suggested that it was made up of two polynucleotide strands, forming a double-helix.]]> 2021-02-05 04:44:06 UTC https://padlet.com/139778/1piwihsgragl9pgp/wish/1166950769 139778 https://padlet.com/139778/1piwihsgragl9pgp/wish/1166950921 James D. Watson and Francis Crick figured out that inside of the backbone of the DNA double helix there were two different types of nitrogenous bases: purines and pyrimidines. They figured out that they are complementary to one another (purines go with pyrimidines and vice versa) rather than being like with like (a purine with a purine or a pyrimidine with a pyrimidine).]]> 2021-02-05 04:44:15 UTC https://padlet.com/139778/1piwihsgragl9pgp/wish/1166950921 139778 https://padlet.com/139778/1piwihsgragl9pgp/wish/1166951399 Frederick Griffith was trying to develop a vaccine against pneumonia by studying two strains of bacterium: a harmless strain and a pathogenic strain. Through this experiment, Griffith found that after he had killed the pathogenic strains of bacteria and then mixed the remains with the living harmless bacteria, some of the living bacteria had become pathogenic. This showed scientists that the pathogenic traits were being passed on to the non-pathogenic cells through heredity.]]> 2021-02-05 04:44:41 UTC https://padlet.com/139778/1piwihsgragl9pgp/wish/1166951399 139778 https://padlet.com/139778/1piwihsgragl9pgp/wish/1166951579 Alfred Hershey and Martha Chase discovered and proved that DNA was responsible for heredity. The thought at the time was that proteins were responsible for heredity and storing genetic information, due to their more complex structure compared to the simple DNA structure. Hershey and Chase did an experiment where they grew two batches of T2 with E.coli. One batch was labeled with radioactive sulfur, and one with radioactive phosphorus. Phosphorus is found in DNA (in the phosphate-sugar backbone that makes up the outer part of its double helical structure) but not in proteins, whereas sulfur is found in most proteins, but not in DNA. Hershey and Chase allowed the two batches of T2 to infect separate samples of non-radioactive bacteria. They then used a blender to shake loose any parts of the phages that remained outside the bacterial cells. They found that when the bacteria had been infected with T2 phages containing labeled protein, the radioactivity ended up mainly in the solution, which contained phages but not bacteria. However, the radioactivity from the phosphorus ended up mostly in a pelet at the bottom of a centrifuge tube. Hershey and Chase proved through this experiment that DNA is responsible for heredity.]]> 2021-02-05 04:44:49 UTC https://padlet.com/139778/1piwihsgragl9pgp/wish/1166951579