Chapter 12 DNA Structure.docx

4 Pages
Unlock Document

University of Toronto Scarborough
Biological Sciences
Effiette Sauer

Chapter 12 DNA Structure, Replication and Organization 12.1a Griffith and Mice  DNA: the molecule that is the genetic material of all living organism  Question: what is the nature of genetic material o Experiment infect mice with S form of an infection (lethal) and R form of the same infection (non-lethal) o 1) injected mice with S form, and mouse dies o 2) injected mice with R form, and mouse lives o 3) injected mice with heat-killed S form, and mice lives o 4) injected mice with heat-killed S cells and R form, mice dies  Living R form can be converted into S form from some factor of the death S form  Conclusion: non-lethal form can be converted into lethal form, through the transforming principle and the process of genetic change transformation 12.1b Avery  Used R and S, labeled Proteins, DNA and RNA, when they destroyed the proteins and RNA same affect happened, but when they destroyed the DNA nothing happened 12.1c Hershey and Chase, Phages and Bacteria  Hershey-Chase experiment determined that DNA held hereditary material  Bacteriophages: are viruses that infect bacteria  Virus: are infectious agents that contain DNA or RNA surrounded by a protein coat o Can only reproduces within a host cell  Phages labeled with radioactive sulfur indicated labeled proteins  Phages labeled with radioactive phosphorous indicated labeled DNA o Because DNA contains phosphorus but not sulfur, and proteins contain sulfur not phosphorus  Radioactive sulfur phages interacted with bacteria, put in blender spun, put in centrifuge,  Supernatant contain radioactivity but bacteria did not,  Radioactive phosphorus phages interacted with bacteria, put in blender spun, put in centrifuge  Supernatant didn’t contain radioactivity, but bacteria did  Thus since phosphorus indicates DNA, the DNA was injected into bacteria, and holds the hereditary material  Transformation: the conversion of a cell’s hereditary type by the uptake of DNA released by the breakdown of another cell 12.2a Watson and Crick  4 nucleotide adenine, thymine, cytosine and guanine  Purines, two carbon rings  Pyrimidine, one carbon ring  Chargaff’s Rule: the number of purines is equal to the number of pyrimidines o Number of A=T number of C=G  Sugar Phosphate Backbone creates the chain that the nucleotides stay on  Phosphate end is the 5’ end, Hydroxyl end in the 3’ end  Each nucleotide contains, phosphate group, deoxyribose sugar and a base  Are held together by phosphodiester bonds  A and T bonds have 2 H bonds  C and G bonds 3 H bonds 12.2b DNA and double helix  Watson and Crick proposed a double stranded DNA in a double helix formation  Double helix model: the two sugar phosphate backbones are separate from each other by a regular distance  Complementary Base pairing: A always bonded to T C always bonded to G, held together by Hydrogen Bonds o This allows the double helix model to maintain constant diameter  Two strands are anti-parallel, that the run in opposite directions one strand is 5’-3’ and the other is 3’-5’ 12.3a Meselson and Stahl  Three theories of DNA replication st o Semiconservative: 1 replication separates the DNA strand and uses each strand as a parent strand in which the new DNA is replicated complementary to it o Conservative Replication: two new separate daughter strands are created keeping father strands intact o Dispersive Replication: original double helix are split into segments and new DNA fills in the missing segments  Old strand serve as template,  Contains the same information as the parent strands 12.3b DNA polymerase  Key molecular evens of DNA replication : o 1. Two strands of DNA molecule unwind for replication to occur o 2. DNA polymerase adds nucleotides to and existing chain o 3. Overall direction of new synthesis is in a 5’-3’ direction which is antiparallel to the template strand o 4. Nucleotides are added using base-pairing rules 12.3c-g  Leading strand is replicated continuously, from 5’-3’  Lagging strand is replicated discontinuously, from 3’-5’ o Because DNA polymerase adds nucleotide to a 3’ end  Helicase unwinds DNA at the replication fork  Primase add RNA primers from 5’-3’  DNA polymerase adds nucleotides 
More Less

Related notes for BIOA01H3

Log In


Don't have an account?

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.