40 Questions
What was the result of treating the mixture with enzymes that destroyed proteins, lipids, carbs, and nucleic acid RNA?
Transformation still occurred
What was the conclusion of Avery and other scientists after observing bacterial transformation?
DNA stores and transmits genetic information
What type of virus did Hershey and Chase study in their experiment?
Bacteriophage
What happens to the bacterium after the bacteriophage injects its genetic information?
The bacterium is destroyed
What was the purpose of the Hershey-Chase experiment?
To determine which part of a virus (protein coat or DNA core) entered bacterial cells
What did Hershey and Chase grow in their experiment?
Bacteriophages
What happens when the bacteriophage injects its genetic information into the bacterium?
The viral genes act to produce many new bacteriophages
What is the outcome of the bacteriophage replication process?
Hundreds of new viruses burst out of the cell
What is the primary function of DNA polymerase in DNA replication?
To join nucleotides to synthesize a new complementary strand of DNA
What is the main reason why cells use telomerase to replicate chromosome ends?
To prevent genes near the ends of chromosomes from being damaged or lost during replication
What was the limitation of Rick's 3D models of molecules?
They didn't explain DNA's properties.
What enabled Watson and Crick to build a model that explained DNA's structure and properties?
Franklin's X-ray pattern.
What is the role of regulatory proteins in prokaryotic DNA replication?
To trigger the start of DNA replication
What is the characteristic of telomerase in cancer cells?
It is activated to enable rapid cell growth and proliferation
What is a key feature of the double helix model?
Antiparallel strands.
What is the significance of the antiparallel strands in the double helix model?
It enables the nitrogenous bases on both strands to come into contact.
What is the function of enzymes in DNA replication?
To carry out DNA replication by breaking hydrogen bonds and unwinding the DNA molecule
What is the characteristic of DNA polymerase in DNA replication?
It is the principal enzyme involved in DNA replication
What is the role of hydrogen bonds in the double helix model?
They hold the two strands of DNA together.
What is the significance of the sequence of nucleotides in the double helix model?
It carries the genetic information.
What is the function of telomeres in eukaryotic chromosomes?
They are the tips of eukaryotic chromosomes that are difficult to replicate
What is the purpose of the double helix model?
To explain the structure of DNA.
What is the characteristic of telomerase in adult cells?
It is switched off to prevent cell growth
What is the relationship between the two strands of DNA in the double helix model?
They are complementary.
What is the reason for the specificity of base pairing between adenine and thymine, and guanine and cytosine?
The shape and size of the nucleotides that fit together
What would happen if the bonds between the two strands of the DNA helix were strong?
The DNA would be impossible to separate
What is the purpose of DNA replication during the S phase of the cell cycle?
To duplicate the DNA before cell division
What is the result of semiconservative DNA replication?
Each new DNA molecule has one new strand and one original strand
What is the role of the original strand in DNA replication?
It serves as a template for the synthesis of a new strand
What is the relationship between the nucleotides on the original strand and the new strand during DNA replication?
The nucleotides on the original strand are complementary to those on the new strand
What is the significance of Chargaff's rule in relation to DNA replication?
It explains the base pairing rules
What is the outcome of the replication process during DNA replication?
Two identical DNA molecules
What was the outcome of many of the injected mice in Griffith's experiment?
They developed pneumonia and died
What was the significance of the lungs being filled with disease-causing bacteria in Griffith's experiment?
It indicated that the transformation was not due to the presence of harmless bacteria
What was Griffith's reasoning behind the mixing of two types of bacteria?
He wanted to identify the chemical factor that transferred the disease-causing ability
What was the conclusion made by Griffith about the transforming factor?
It was a gene that carried the information for the disease-causing ability
Who led the group of scientists at the Rockefeller Institute to repeat Griffith's work?
Oswald Avery
What was the goal of the Rockefeller Institute scientists in repeating Griffith's work?
To identify the molecule responsible for the transformation
What was the result of the Rockefeller Institute scientists' experiment?
They discovered that the molecule was a type of DNA
What is the term used to describe the process of transferring genetic information from one type of bacteria to another?
Transformation
Study Notes
DNA Replication and Structure
- Guanine is always paired with cytosine in DNA replication
- Enzymes, particularly DNA polymerase, play a crucial role in carrying out DNA replication
- First, the enzyme "unzips" the molecule of DNA by breaking hydrogen bonds between base pairs and unwinding the two strands of the molecule
- Then, it joins nucleotides to synthesize a new complementary strand of DNA
Telomeres
- Telomeres are the tips of eukaryotic chromosomes
- Because the ends of DNA molecules are difficult to replicate, cells use a special enzyme called telomerase to do the job
- Telomerase adds short, repeated DNA sequences to telomeres as chromosomes are replicated
- This helps prevent genes near the ends of chromosomes from being damaged or lost during replication
Replication in Living Cells
- Prokaryotic DNA replication begins when regulatory proteins bind to a single starting point on the chromosome
- The process triggers the replication of DNA
Discovery of DNA Structure
- James Watson and Francis Crick built a model of DNA based on X-ray patterns taken by Rosalind Franklin
- Their model explained the specific structure and properties of DNA
- The double helix model consists of two strands of nucleotide sequences wound around each other
- The strands are antiparallel, meaning they run in opposite directions
- Hydrogen bonds form between certain nitrogenous bases, providing enough force to hold the two strands together
- Base pairing follows Chargaff's rule: adenine with thymine and guanine with cytosine
DNA Replication Process
- Before a cell divides, it duplicates its DNA during the S phase of the cell cycle
- The two strands of each DNA molecule separate, and then two complementary strands are synthesized following the rules of base pairing
- Each strand of the double helix of DNA serves as a template/model for the new strand
- DNA replication is semiconservative, meaning each DNA molecule resulting from replication has one of the two original strands and one new strand
Transformation
- Griffith's experiment showed that heat-killed bacteria can pass their disease-causing ability to harmless bacteria
- The transforming factor was identified as a gene, which is made up of DNA
Molecular Cause of Transformation
- Avery's experiment showed that DNA is the molecule responsible for transformation
- Enzymes that destroyed proteins, lipids, carbohydrates, and nucleic acid RNA did not prevent transformation, but enzymes that broke down DNA did
- This led to the conclusion that DNA stores and transmits genetic information from one generation of bacteria to the next
This quiz covers the process of DNA replication, the role of enzymes in the process, and the specific ways they facilitate the replication of DNA molecules.
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