Evidence as the Genetic Material
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a. __ discovered the double- helical model for DNA
b. Nucleic acids are unique in their ability to__
i. Hereditary info is encoded in the __and __in all the cells of your body
- Watson and Crick
- direct their own replication from monomers
- chemical language of DNA
a. Searching for the Genetic Material
i. __ showed that genes exist as parts of chromosomes
1. What was the general belief?
Disproved through study of bacteria and viruses that infect them
- T.H. Morgan
- proteins, due to great heterogeneity and specificity of function, were hereditary material; nucleic acids too uniform
i. Discovery of the genetic role of DNA when attempt to develop a vaccine against __ carried out by __
- pneumonia (streptococcus
- Frederick Griffith
Explain the Griffith experiment.
- a. Had two strains: one pathogenic, one harmless
- b. Living S cells injected: dead mouse
- c. Living R cells injected: living mouse
- d. Dead S cells: living mouse
- e. Mixture of dead S cells and living R cells: dead mouse
- i. Some living cells became pathogenic through transformation (a change in the genotype and phenotype due to the assimilation of external DNA by a cell)
- ii. Pathogenicity trait inherited by all descendants
Explain Oswald Avery's experiment.
- a. Wanted to identify transforming substance
- i. DNA, RNA, protein
- ii. Broke open heat-killed pathogenic bacteria and extracted cell contents, inactivating each molecule, and testing ability to transform
- 1. Only DNA= Avery, MacLeod, McCarthy discovered transforming agent was DNA
Explain Hershey and Chase's experiment
- a. Used phages because viruses are much simpler cells with DNA and a protein coat
- b. Used T2 ( infects E. coli and turns it into a T2-producing factory
- c. Used radioactive sulfur to tag protein and radioactive phosphorus to tag DNA in separate batches
- i. Found that phage DNA entered the host cells but the phage protein did not
- 1. Also, when returned to a culture medium, the infection ran its course, and E. coli released phages that contained some radioactive phosphorus, showing DNA played a part of the infection process
a. Analyzed base composition of DNA and reported that base composition of DNA __from one species to the next and analyzed ratios of bases
i. Adenine amounts are equal to __ amounts/ cytosine amounts are equal to __ amounts
1. Led to __:
a. what are they?
- Erwin Chargaff
- Chargoff’s rules:
- 1) base composition varies between species
- 2) Within a species, the number of A and T bases are equal, and the number of C and G bases are equal
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