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Questions and Answers
What is the key difference between the S (smooth) and R (rough) strains of Pneumococcus identified by Frederick Griffith?
What is the key difference between the S (smooth) and R (rough) strains of Pneumococcus identified by Frederick Griffith?
- The S strain is genetically stable, while the R strain can undergo genetic mutations.
- The S strain is more resistant to antibiotics compared to the R strain.
- The S strain has a polysaccharide capsule, while the R strain lacks this capsule.
- The S strain is virulent and causes fatal pneumonia, while the R strain is avirulent and does not cause illness. (correct)
Which of the following was the key finding from Griffith's transformation experiment?
Which of the following was the key finding from Griffith's transformation experiment?
- Avirulent R strains of Pneumococcus could be transformed into virulent S strains.
- The transforming principle was likely a component of the polysaccharide capsule or a compound required for capsule synthesis.
- Genetic material could be transferred between bacterial cells, leading to changes in phenotype.
- All of the above were key findings from Griffith's transformation experiment. (correct)
Why did geneticists in the 1940s favor proteins as the genetic material rather than DNA?
Why did geneticists in the 1940s favor proteins as the genetic material rather than DNA?
- Proteins were thought to be more stable and less prone to mutations than DNA.
- DNA had not yet been identified as the hereditary molecule at that time.
- Proteins were believed to have a more complex structure that could better encode genetic information.
- Proteins were known to be more abundant and diverse in cells compared to DNA. (correct)
What was the key finding from the Hershey-Chase experiment using bacteriophage T2?
What was the key finding from the Hershey-Chase experiment using bacteriophage T2?
What is the difference between a nucleoside and a nucleotide?
What is the difference between a nucleoside and a nucleotide?
What are Chargaff's rules of base composition in DNA?
What are Chargaff's rules of base composition in DNA?
What is the role of phosphodiester bonds in the structure of DNA?
What is the role of phosphodiester bonds in the structure of DNA?
What are the four characteristics that the genetic material must exhibit?
What are the four characteristics that the genetic material must exhibit?
When were Mendel's hereditary principles rediscovered?
When were Mendel's hereditary principles rediscovered?
Who independently described the parallels between chromosome partitioning into gametes and the inheritance of genes?
Who independently described the parallels between chromosome partitioning into gametes and the inheritance of genes?
In what year was DNA localized to chromosomes and made a candidate for the hereditary material?
In what year was DNA localized to chromosomes and made a candidate for the hereditary material?
Why were both proteins and RNA also considered candidates for the hereditary material?
Why were both proteins and RNA also considered candidates for the hereditary material?
Which criteria must a molecule meet to serve as genetic material?
Which criteria must a molecule meet to serve as genetic material?
Why were lipids and carbohydrates also considered candidates for the hereditary material?
Why were lipids and carbohydrates also considered candidates for the hereditary material?
Which experimental result provided crucial data for Watson and Crick's DNA model?
Which experimental result provided crucial data for Watson and Crick's DNA model?
Which of the following statements about DNA is correct according to the information provided?
Which of the following statements about DNA is correct according to the information provided?
What did Rosalind Franklin's X-ray diffraction analysis reveal about the structure of DNA?
What did Rosalind Franklin's X-ray diffraction analysis reveal about the structure of DNA?
According to the Watson and Crick model, what is the structure of DNA?
According to the Watson and Crick model, what is the structure of DNA?
What did James Watson and Francis Crick receive for their DNA model?
What did James Watson and Francis Crick receive for their DNA model?
Which of the following statements about DNA is NOT supported by the information provided?
Which of the following statements about DNA is NOT supported by the information provided?
Who was the British biophysicist and X-ray crystallographer whose experimental work contributed to the discovery of DNA's structure?
Who was the British biophysicist and X-ray crystallographer whose experimental work contributed to the discovery of DNA's structure?
How many hydrogen bonds are formed between adenine (A) and thymine (T) in DNA base pairing?
How many hydrogen bonds are formed between adenine (A) and thymine (T) in DNA base pairing?
Which type of bond is present between guanine (G) and cytosine (C) in DNA base pairing?
Which type of bond is present between guanine (G) and cytosine (C) in DNA base pairing?
In the structure of DNA, what makes up the backbone of the molecule?
In the structure of DNA, what makes up the backbone of the molecule?
Which scientist(s) proposed the DNA double helix structure?
Which scientist(s) proposed the DNA double helix structure?
What experiment helped in establishing that DNA is the genetic material?
What experiment helped in establishing that DNA is the genetic material?
In Chargaff's rules of base composition, what is the ratio of adenine (A) to thymine (T)?
In Chargaff's rules of base composition, what is the ratio of adenine (A) to thymine (T)?
Which direction do DNA strands run in, as indicated by the notation 5’-3’?
Which direction do DNA strands run in, as indicated by the notation 5’-3’?
What provides complementarity to the two strands of DNA?
What provides complementarity to the two strands of DNA?
Which type of bond is responsible for providing chemical stability to the DNA helix?
Which type of bond is responsible for providing chemical stability to the DNA helix?
Study Notes
Griffith's Transformation Experiment
- Frederick Griffith (1927) showed that avirulent strains of Streptococcus pneumoniae could be transformed to virulence
- He speculated that the transforming principle could be part of the polysaccharide capsule or a compound required for capsule synthesis
Avery, MacLeod, and McCarty's Experiment
- Demonstrated that DNA is the genetic material (1944)
- Used Streptococcus pneumoniae to show that DNA is the transforming principle
Hershey and Chase Experiment
- Used Escherichia coli and bacteriophage T2 to show that DNA enters the bacterial cell during infection and directs viral reproduction (1952)
- Demonstrated that DNA, not protein, is the genetic material
Composition and Structure of DNA
- Nucleotides are the building blocks of DNA
- Nucleotides consist of a nitrogenous base, pentose sugar, and phosphate group
- DNA contains deoxyribose, while RNA contains ribose sugar
Nucleosides and Nucleotides
- Nucleoside: a nitrogenous base and pentose sugar
- Nucleotide: a nucleoside with a phosphate group added
- Mono-, di-, and triphosphates: nucleotides with one, two, or three phosphate groups added
Phosphodiester Bonds
- Nucleotides are linked by phosphodiester bonds between the phosphate group at the C-5' position and the OH group at the C-3' position
Erwin Chargaff's Rules of Base Composition
- A = T, and G = C
- The amount of pyrimidine nucleotides (T+C) equals the amount of purine nucleotides (A+G)
Watson and Crick's Model
- Proposed structure of DNA as a double helix (1953)
- Two anti-parallel strands connected by base pairing, with stacked nitrogenous bases
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Description
Test your knowledge on topics like the structure and replication of DNA, evidence supporting DNA as the genetic material, and the chemistry essential to DNA structure. Explore the criteria for a molecule to serve as genetic material and the rediscovery of Mendel's work in genetics.
