120 likes | 128 Views
12 – 1 DNA. Hershey-Chase Experiment A. Studied viruses in 1952 B. Bacteriophage are composed of DNA or RNA and inject it into a host cell C. Determined the genetic material of the bacteriophage was DNA. 2. Rosalind Franklin’s X-ray A. Studied DNA in 1950’s
E N D
Hershey-Chase Experiment A. Studied viruses in 1952 B. Bacteriophage are composed of DNA or RNA and inject it into a host cell C. Determined the genetic material of the bacteriophage was DNA
2. Rosalind Franklin’s X-ray A. Studied DNA in 1950’s B. Used X-ray diffraction to get information about the structure of DNA C. Was able to stretch DNA sample and obtain a clear pattern on film. D. The x-shaped pattern shows the strands are twisted around each other 1. Called a helix 2. Angle suggest that there are two strands
3. Watson and Crick A. Studied the structure of DNA B. Could not figure out structure until they saw Franklin’s X-ray image C. 1953 the structure of DNA was finally known D. Watson wrote: “The instant I saw the picture my mouth fell open and my pulse began to race.” E. Watson and Crick’s model of DNA was a double helix, in which two strands were wound around each other.
4. DNA – Genetic material of living organisms and is located in the chromosomes of each cell. A. DNA is made of two chains of repeating subunits called nucleotides B. Each nucleotide consists of three parts: 1. Deoxyribose: a 5-carbon sugar molecule 2. A phosphate group: made of P surrounded by oxygen 3. Nitrogenous base: basic molecule that contains nitrogen
5. Four nitrogenous bases A. Purines (2 carbon rings) 1. Adenine = A 2. Guanine = G B. Pyrimadines (1 carbon ring) 1.Cytosine = C 2. Thymine = T
6. The Double Helix A. Made of two nucleotide chains that wrap around each other to form a spiral staircase. B. Backbone - Alternating sugar and phosphate groups. C. Rungs - Hydrogen bonds hold opposing bases to each other, perpendicular to backbone.
7.Complementary Base Pairing A. Base-pairing rules: 1.Cytosine always bonds with guanine a.3 hydrogen bonds b. C - G 2. Adenine always bonds with thymine a. 2 hydrogen bonds b. A - T B. One purine bonds with one pyrimadine