8.1 Study Guide Flashcards
What process was discovered as a result of Frederick Griffith’s experiments? What disease did he use to test this process?
Fredrick Griffith discovered the process of bacterial transformation as a result of his experiments. To do this, he tested different strains of pneumonia on mice.
What was the goal of Avery, Macleod, and McCarty’s experiments? Why were their results subject to skepticism by the scientific community?
The goal of Avery, Macleod, and McCarty’s experiments was to determine the primary biomolecule responsible for heredity. Their results were subject to skepticism because it was possible that the substances they tested could have been contaminated in ways that would have largely affected their results.
What was the goal of the Hershey-Chase experiments? What difference from the Avery experiments ensured their results were accurate?
The goal of the Hershey-Chase experiments was also to determine the primary biomolecule responsible for heredity. To ensure their results were accurate, their experiment was constructed so that the tested substances were unable to be accidentally contaminated.
Name the three sections of a nucleotide.
- Phosphate Group
- Pentose Sugar (Deoxyribose or Ribose)
- Nitrogenous Base
What shape does the structure of DNA form into?
The structure of DNA naturally forms into a double-helix shape.
State at least three structural differences between DNA and RNA.
- DNA forms into a double-helix shape, while RNA forms into a single-helix shape (or other shapes concerning different types of RNA).
- The sugar in DNA is Deoxyribose, while the sugar in RNA is Ribose.
- The DNA bases are Adenine, Cytosine, Guanine, and Thymine, while the RNA bases are Adenine, Cytosine, Guanine, and Uracil.
- RNA can fold in on and bond with itself, while DNA cannot.
Recall the Griffith experiments. How did Griffith prove the existence of bacterial transformation?
To prove the existence of bacterial transformation, Frederick Griffith used a lethal strain and a non-lethal strain of pneumonia to demonstrate that the presence of the lethal strain, even in a dead form, and the non-lethal strain in mice can stimulate the transformation of the non-lethal strain into the lethal strain.
Recall the Avery, Macleod, and McCarty experiments. How did these scientists attempt to prove which primary biomolecule is responsible for heredity?
While Griffith proved the existence of bacterial transformation, it was still unclear which primary biomolecule was responsible for the transportation of genetic material from one strain of bacteria to another. Attempting to determine this, Avery, MacLeod, and McCarty replicated bacterial transformation in multiple experiments, one without proteins, one without RNA, and one without DNA (as carbohydrates and lipids had been essentially disqualified as possibilities). Their results showed that bacterial transformation could not occur without the presence of DNA only, but the scientific community was skeptical, as it was possible that the tested substances could have been contaminated with the wrong biomolecules.
Recall the Hershey-Chase experiments. How did these scientists definitively prove which primary biomolecule is responsible for heredity?
As the accuracy of the results of the Avery experiments was unclear, the Hershey-Chase experiments attempted to more definitively determine the biomolecule of heredity. To do this, Hershey and Chase tested viruses instead of bacteria. In one experiment, they marked the virus DNA with radioactive Phosphorus-32, making it glow. In another, they marked the virus protein shell with radioactive Sulfur-35, making it glow as well. Next, they infected cells with the viruses and used a centrifuge to separate the cells from the empty virus bodies. By doing this, they could demonstrate visually that it was the virus DNA that entered the cells and transformed them as opposed to proteins, proving that DNA was the biomolecule responsible for heredity (at least in viruses).
If an organism’s DNA sequence consists of 22.4% adenine, what percentage of the sequence is made up of each of the other three bases?
Thymine: 22.4%
Cytosine: 27.6%
Guanine: 27.6%
