Textbook Notes (368,318)
Canada (161,798)
York University (12,828)
Biology (1,015)
BIOL 1000 (389)
Chapter 13


5 Pages
Unlock Document

BIOL 1000
Julie Clark

Tanya Sivamanoharan Wed, Sept, 28/11 Biology- Chap #13 Notes DNA STRUCTURE, REPLICATION, AND ORGANIZATION 13.1- Establishing DNA as the Heredity Molecule -in 1 hlf. of 20th century scientist thought proteins were heredity molec. b/c they had 23 diff. amino acids and nucleic acids had only 4 diff. nitrogenous bases -DNA is however the genetic material to heredity 13.1a- Experiments Began When Griffith Found a Substance That Could Genetically Transform Pneumonia Bacteria -in 1928, Frederick Griffith did an experiment with mice and the bacterium Streptococcus pneumonia -he was finding a vaccine to prevent pneumonia -he had 2 types of the bacteria (S cells and R cells) -S cells smooth strain with polysaccharide capsule surrounding each cell -R cells do not have polysaccharide capsule surrounding each cell -mice injected with infective S cells: mice die therefore S cells are virulent -mice injected with infective R cells: mice live therefore R cells are nonvirulent -mice injected with heated S cells: mice live therefore dead S cells are nonvirulent -mice injected with heated S cells and R cells: mice die therefore residue from dead S cells change R cells to be virulent - therefore Griffith concluded that dead S cells could change living R cells to become virulent -the S cell was called the transforming principle and the process of genetic change transformation 13.1b- Avery and His Co-workers Identified DNA as the Molecule That Transforms Rough Streptococcus to the Infective Form -in 1940S, Oswald Avery performed experiment to study chem. change of the S cell to the R cell -They killed the S bacteria and added enzymes that broke down the 3 molecules for heredity material: DNA, RNA, and proteins -when they destroyed RNA or proteins it did not stop the S cells from transforming R cell into virulent bacteria -when they destroyed DNA, the transformation did not happen -they concluded that the transforming principle was DNA 13.1c- Hershey and Chase Found the Final Evidence Establishing DNA as the Heredity Molecule -in 1952 Alfred D. Hershey and Martha Chase did an experiment on DNA -they studied the E.coli bacteria that was infected by a T2 bacteriophage virus cell that contained DNA surrounded by proteins -the T2 phage that Hershey and Chase studied had a DNA molecule with a protein coat -this meant that one of the 2: DNA or protein hade to go into the host cell in order for the virus to replicate -Hershey and Chase took 2 batches of T2 bacteria: one with DNA having the radioactive tag and the other with proteins having the radioactive tag -then they infected 2 sets of E.coli bacteria with the 2 separate batches of T2 -when they infected E.coli with the labeled protein coat, they found no radioactivity in the cell -whereas, when they infected E.coli with the labeled DNA, they found radioactive material inside the cell -this lead to the conclusion that DNA was what entered the E.coli cell and was the genetic information for reproduction -the experiments of Griffith, Avery, and Hershey and Chase established the term transformation -transformation the conversion of a cell’s heredity type by the uptake of DNA released by the breakdown of another cell 13.2- DNA Structure -in 1953 Watson and Crick discovered the structure of DNA 13.2a-Watson and Crick Brought Together Information from Several Sources to Work Out DNA Structure -DNA contains 4 diff. nucleotides -each nucleotide is made of a phosphate group, a 5-carbon sugar deoxyribose, and a nitrogenous base -the 4 nitrogenous bases are adenine, thymine, cytosine, guanine -purine adenine and guanine built by a pair of fused rings of carbon and nitrogen atoms -pyrimidine thymine and cytosine built from a single carbon ring -Chargaff’s rule the nitrogenous bases pair up as A + T and C+G, therefore purines= pyrimidines in a DNA molecule -DNA forms as a polynucleotide chain with a sugar-phosphate backbone -each phosphate group in DNA is a bridge between the 3’carbon on one sugar and the 5’ carbon on the next sugar, this entire linkage is called a  phosphodiester bond -the ends of the polynucleotide chain of a DNA have a 3’ end with a hydroxyl groupd and a 5’ end with a phosphate group -Watson and Crick used the research done by Rosalind Franklin and Maurice Wilkins to interpret the double –helix shape of the DNA -the 2 scientists used x-ray diffraction to study DNA shape -the x-ray patterns indicated that DNA was cylindrical and was about 2 nm in diameter -Franklin saw an x-shape of the DNA in the diffraction image, so she said that DNA was helical 13.2b- The New Model Proposed That Two Polynucleotide Chains Wind into a DNA Double Helix -Watson and Crick arranged the nucleotides in DNA in order to match the prediction of Frankliin and they ended up with a double stranded helical DNA -this becam
More Less

Related notes for BIOL 1000

Log In


Join OneClass

Access over 10 million pages of study
documents for 1.3 million courses.

Sign up

Join to view


By registering, I agree to the Terms and Privacy Policies
Already have an account?
Just a few more details

So we can recommend you notes for your school.

Reset Password

Please enter below the email address you registered with and we will send you a link to reset your password.

Add your courses

Get notes from the top students in your class.