Honor Bio 8.1 Flashcards
What was the setup of Griffith’s experiment?
Griffith used two strains of Streptococcus pneumoniae: the smooth (S) strain, which is virulent and has a polysaccharide capsule, and the rough (R) strain, which is non-virulent and lacks the capsule. He injected mice with different combinations of live and heat-killed bacteria to observe the effects.
What was the setup of Avery, MacLeod, and McCarty’s experiment?
They used extracts from the S strain of Streptococcus pneumoniae and treated them with enzymes that destroyed proteins, RNA, and DNA separately. They then tested the ability of each treated extract to transform the R strain into the S strain.
What was the setup of Hershey and Chase’s experiment?
They used bacteriophages (viruses that infect bacteria) labeled with radioactive phosphorus (^32P) for DNA and radioactive sulfur (^35S) for proteins. They infected bacteria with these phages and then separated the viral coats from the bacteria to determine which radioactive material entered the bacterial cells.
What are the three main parts of a nucleotide?
A nucleotide consists of a phosphate group, a sugar (deoxyribose in DNA and ribose in RNA), and a nitrogenous base (adenine, thymine, cytosine, guanine in DNA; adenine, uracil, cytosine, guanine in RNA).
Describe the structure of a DNA molecule.
DNA is a double helix composed of two complementary strands of nucleotides. The strands are held together by hydrogen bonds between the nitrogenous bases (A-T and C-G). The sugar-phosphate backbone runs along the outside of the helix.
What are the similarities and differences between DNA and RNA?
Similarities: Both are nucleic acids, both are made up of nucleotides, and both contain adenine, cytosine, and guanine.
Differences: DNA contains thymine, while RNA contains uracil. DNA is double-stranded, while RNA is usually single-stranded. DNA has deoxyribose sugar, while RNA has ribose sugar.
What did Griffith’s experiment demonstrate, and why was it significant?
Griffith’s experiment demonstrated the phenomenon of transformation, where genetic material from the heat-killed S strain could transform the non-virulent R strain into a virulent form. This suggested the presence of a “transforming principle,” later identified as DNA, which carries genetic information.
How did Avery, MacLeod, and McCarty’s experiment build on Griffith’s findings, and what did they conclude?
They identified the “transforming principle” as DNA by systematically destroying proteins, RNA, and DNA in the S strain extract. When DNA was destroyed, transformation did not occur, leading them to conclude that DNA is the material responsible for heredity.
What did Hershey and Chase’s experiment prove, and how did it contribute to the understanding of DNA?
Hershey and Chase proved that DNA, not protein, is the genetic material that enters bacterial cells during phage infection. This was shown by the presence of ^32P (DNA) inside the bacteria, while ^35S (protein) remained outside, confirming DNA’s role in heredity.
