BIOL 2311 Lecture Notes - Lecture 13: Guanine, Polynucleotide, Thymine
DNA structure
Hammerling exp:
cut a piece of each type of algeag and grafted it on the other one. The caps of the algea doesn’t change.
The control of the structure of the cap is present in the lowr half- the base.
Hammerling cuts the stall of Crenulata and medterranea: which are 2 type sof green algea. Swaps the
stalls- the base and cap color the same even though stalls switched. Discovered hereditary info is stored
in the nucleus.
Griffth exp:
-Streptococcus pneumoniae bacterium (the micro-organism that was used) causes severe pneumonia
-Used two strains of bacterium:
R- rough (R) strain is nonvirulent (noninfective, or nonpathogenic), mice live.
S- smooth (S) strain is virulent (highly infective, or pathogenic), mice die.
-4 types performed: heat killed S strain (lives), nonvirulent R strain (lives), virulent S strain (dies), and
heatkilled S strain +nonvirulent R strain(dies). This showed tht The blood contained live pathogenic s.
pneuominae.
Concluded tht: some transforming principle was changing the nonvirulent R form into the S form even
though S strain was killed.
-movement of genes from one to another organism: recpeint cell (non-virulent strain) to donor cell
-movement of the genes can alter the gentic makeup of the recipient cell
Avery Exp: wht material caused the death of the mice?
Mixed the heat killed virulent and regular nonvirulent strains and treated them with either protease
(kills all protein- mice dies) or DNase (enzyme tht chews up the DNA- mice lives).
With Protease (which kills all the protein)- the mice still dies. Showing that there is something else other
than protein thts causing th mice to die.
With the DNase (an enzyme tht chews up the DNA)- the mice lives. Showing tht the the DNA was wht
was causing the mice to die.
Conlcusion: DNA is the genetic Molecule That Transforms Nonvirulent Streptococcus Bacteria to the
Virulent Form.
(So basically DNA is the transforming agent allowing R bacteria to make a smooth coat and allow
infection to kill the mice).
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hershey-chase exp:
studied the infection of the bacterium E coli
Bacteriophages (phages) are viruses that infect the bacteria. They make the bacteria bad.
These bacteriophage viruses have a protein head and DNA core ONLY.
These bacteripohage viruses use the e coli bacteria to produce more of itself.
EXP:
1) virus infects by injecting DNA into bacterial cell to amplify the bacteripophage effect
2) This machinery will be used to make viral proteins and viral DNA
3) The viral DNA will be packaged into protein capsid structure: virions
4) This bacterial cell will break open (lysis) the virions will be released which will be able to affect
the other bacterial cells.
either DNA or protein must be the genetic material that enters the bacterial cell and directs the infective
cycle within. But which one?
The protein of the virus labeled- radioactive sulfur.
The DNA of the virus labeled- radioactive phosphorus
1) The e coli was grown in two separate mediums of radioactive phosphorous and radioactive
sulfur.
2) Then the culutres were infected with the bacteriophage viruses.
3) Centrifuged the material after genetic material allowed to enter the bacteria.
4) Supernatant (phage coats tht did not enter the bacteria) and the pellets (cell debris).
5) In the S35 environment, radioacitivty found in supernatant. In P32, radioacitivty found in pellets.
Results: Their results showed that most of the labeled DNA, but little of the labeled protein, entered the
cell and appeared in progeny phages.
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*Transformation is the alteration of a cell’s hereditary type by the uptake of DNA released by the
breakdown of another cell.
DNA structure:
A nucleic acid
Composed of nucleotides : nitorgenous base (adenine, guanine, thymine, or cytosine) and deoxyribose
sugar (If OH in sugar its RNA, H in suagr is DNA) and phsophate group
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Document Summary
Dna structure cut a piece of each type of algeag and grafted it on the other one. The control of the structure of the cap is present in the lowr half- the base. Hammerling cuts the stall of crenulata and medterranea: which are 2 type sof green algea. Swaps the stalls- the base and cap color the same even though stalls switched. Discovered hereditary info is stored in the nucleus. Streptococcus pneumoniae bacterium (the micro-organism that was used) causes severe pneumonia. R- rough (r) strain is nonvirulent (noninfective, or nonpathogenic), mice live. S- smooth (s) strain is virulent (highly infective, or pathogenic), mice die. 4 types performed: heat killed s strain (lives), nonvirulent r strain (lives), virulent s strain (dies), and heatkilled s strain +nonvirulent r strain(dies). This showed tht the blood contained live pathogenic s. pneuominae. Concluded tht: some transforming principle was changing the nonvirulent r form into the s form even though s strain was killed.
