19 Questions
What did Frederick Griffith identify as the two strains of Pneumococcus?
S and R strains
In Griffith's transformation experiment, what could a single gene mutation change do?
Convert an avirulent strain to a virulent strain
According to geneticists in the 1940s, what was favored as genetic material?
Proteins
What did Hershey and Chase demonstrate in their experiment using Escherichia coli and bacteriophage T2?
DNA enters bacterial cell during infection and directs viral reproduction
What type of sugar is present in DNA but not in RNA?
Deoxyribose sugar
What did Rosalind Franklin's X-ray diffraction studies reveal about DNA structure?
DNA has a 3.4-angstrom periodicity, characteristic of a helical structure
Which scientist's base composition analysis provided crucial data to Watson and Crick for their DNA model?
Chargaff
According to Watson and Crick's model, how are the two DNA strands connected?
By hydrogen bonding
What did Watson and Crick propose about the structure of DNA?
Double helix with anti-parallel strands
What was the Nobel Prize awarded to James Watson and Francis Crick for in 1962?
Discovery of the DNA double helix structure
What are the four key characteristics that the genetic material must exhibit?
Replication, storage of information, expression of information, and variation by mutation
Which two scientists independently described the parallels between chromosome partitioning into gametes and the inheritance of genes?
Walter Sutton and Theodor Boveri
What was the evidence that made DNA a candidate for the hereditary material?
DNA was localized to chromosomes
In what year were Mendel's hereditary principles rediscovered?
1900
How many hydrogen bonds are formed between a guanine (G) and cytosine (C) base pair?
3
Which of the following statements about the DNA structure is correct?
The two strands of the DNA helix run in opposite directions (antiparallel).
Which of the following experiments provided evidence for the structure of DNA?
All of the above
What is the significance of Chargaff's rules of base composition in the discovery of the DNA structure?
It revealed the complementary base pairing between A-T and G-C.
Who were awarded the Nobel Prize in 1962 for their contribution to the discovery of the DNA structure?
James Watson and Francis Crick
Study Notes
Griffith's Transformation Experiment
- Frederick Griffith identified two strains of Pneumococcus: S (smooth) and R (rough)
- S strain is virulent and causes fatal pneumonia in mice, while R strain is avirulent
- A single gene mutation can convert an S strain to an R strain
The Avery, MacLeod, and McCarty Experiment
- Experiment in 1944 showed that DNA is the hereditary molecule
- Provided foundation for understanding the transforming principle
Hershey-Chase Experiment
- Experiment in 1952 used Escherichia coli and bacteriophage T2
- Used radioisotopes 32P and 35S to demonstrate DNA enters bacterial cell during infection and directs viral reproduction
- Demonstrated that DNA, not protein, is the genetic material
Structure of DNA
- Nucleotides consist of a nitrogenous base, pentose sugar, and phosphate group
- Nucleosides contain nitrogenous base and pentose sugar
- Nucleotides are linked by phosphodiester bonds between phosphate group at C-5' position and OH group on C-3' position
Erwin Chargaff's Rules of Base Composition
- The amount of T = A, the amount of C = G
- The amount of pyrimidine nucleotides (T+C) = purine nucleotides (A+G)
Rosalind Franklin's X-ray Diffraction Analysis
- X-ray diffraction analysis of DNA showed a 3.4-angstrom periodicity, characteristic of a helical structure
- Data provided crucial information for Watson and Crick's model of DNA
Watson and Crick's Double Helix Model
- Proposed structure of DNA as a double helix with two anti-parallel strands connected by base pairing
- Stacked nitrogenous bases and sugar-phosphate backbone form the structure of DNA
This quiz covers topics related to DNA structure, replication, nucleic acid chemistry, evidence supporting DNA as the genetic material, RNA structure, and criteria for genetic material. It also includes information about Mendel's rediscovery.
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