Podcast
Questions and Answers
Which of the following statements is false about the DNA backbone?
Which of the following statements is false about the DNA backbone?
- The backbone is not straight, but twisted into a spiral shape
- The DNA backbone is composed of alternating sugar and phosphate groups
- The DNA backbone includes the nitrogenous bases held together by hydrogen bonds (correct)
- The two backbones run in opposite directions
The sugar-phosphate backbone of DNA is oriented in opposite directions from each other.
The sugar-phosphate backbone of DNA is oriented in opposite directions from each other.
True (A)
An interpretation of Griffith's experiments is that _____________
An interpretation of Griffith's experiments is that _____________
fragments of DNA containing genes were taken up by the R-strain bacteria.
What is the correct order of events in DNA replication?
What is the correct order of events in DNA replication?
The two strands of the DNA double helix are held together by _______________
The two strands of the DNA double helix are held together by _______________
Many scientists had trouble believing that DNA was the genetic material because _______________
Many scientists had trouble believing that DNA was the genetic material because _______________
DNA polymerase _____________
DNA polymerase _____________
What can cause errors to accumulate in DNA?
What can cause errors to accumulate in DNA?
The structure of DNA explained Chargaff's observations because __________
The structure of DNA explained Chargaff's observations because __________
DNA replication is a semiconservative process because _________________
DNA replication is a semiconservative process because _________________
If 10% of the nucleotides in a newly discovered bacterium's DNA are adenine (A), what percentage of nucleotides is guanine?
If 10% of the nucleotides in a newly discovered bacterium's DNA are adenine (A), what percentage of nucleotides is guanine?
How can a cell, killed by heat, still transform a second strain of bacteria?
How can a cell, killed by heat, still transform a second strain of bacteria?
What is responsible for determining the size of a chromosome?
What is responsible for determining the size of a chromosome?
The sugars and phosphates in the 'backbone' of a DNA strand are held together by _____________
The sugars and phosphates in the 'backbone' of a DNA strand are held together by _____________
Which parts of a nucleotide are touched when climbing a model of DNA?
Which parts of a nucleotide are touched when climbing a model of DNA?
The two strands of DNA that make up a double helix are complementary to each other.
The two strands of DNA that make up a double helix are complementary to each other.
Multiple replication bubbles on a single eukaryotic chromosome ______________
Multiple replication bubbles on a single eukaryotic chromosome ______________
Which of the following statements about a DNA helix is false?
Which of the following statements about a DNA helix is false?
Identify the research that first provided the basis for the statement: 'DNA is the genetic material.'
Identify the research that first provided the basis for the statement: 'DNA is the genetic material.'
Which of the following is a type of mutation in which a section of DNA is cut out and inserted elsewhere?
Which of the following is a type of mutation in which a section of DNA is cut out and inserted elsewhere?
Which of the following statements is false?
Which of the following statements is false?
The purpose of DNA replication is to produce _____________
The purpose of DNA replication is to produce _____________
Which of the following events occurs within a DNA replication bubble?
Which of the following events occurs within a DNA replication bubble?
DNA ligase has all of the functions listed except ____________
DNA ligase has all of the functions listed except ____________
Information in DNA is carried in the ______________
Information in DNA is carried in the ______________
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Study Notes
DNA Structure and Function
- The backbone of DNA consists of alternating sugar and phosphate groups, not nitrogenous bases.
- DNA strands run in opposite directions (antiparallel), allowing for proper base pairing.
- Hydrogen bonds form between complementary bases (adenine with thymine, cytosine with guanine), stabilizing the double helix structure.
DNA Replication
- The process is semiconservative, with each new DNA molecule containing one old and one new strand.
- Key stages of replication include unwinding of the helix by enzymes and synthesis of new complementary strands by DNA polymerase.
- Multiple replication bubbles form on eukaryotic chromosomes, facilitating rapid replication.
Genetic Transformation
- Griffith's experiments indicated that heat-killed bacteria could transform non-pathogenic strains into pathogenic ones through DNA uptake.
- Avery, McLeod, and McCarty confirmed DNA as the genetic material by isolating the transforming substance in R-strain bacteria.
Mutations and Errors
- DNA mutations can accumulate due to environmental factors like ultraviolet light.
- Translocation is a mutation type where a DNA segment is cut out and inserted elsewhere.
Base Pairing and Chargaff's Rules
- Chargaff's observations highlighted that adenine pairs with thymine and cytosine with guanine, maintaining consistent base quantities across DNA.
- A DNA strand's nucleotide composition affects the pairing rules and overall structure.
DNA Enzymes and Bonds
- DNA polymerase can only add nucleotides to the free sugar end of a growing DNA strand.
- Covalent bonds link sugars and phosphates in the DNA backbone, ensuring structural integrity.
DNA Structure Characteristics
- The double helix structure resembles a twisted ladder, with nitrogenous bases forming the rungs.
- Two DNA strands are complementary, allowing for precise replication and function.
Additional Insights
- The smallest human chromosome (Y) is significantly smaller than the largest ( chromosome 1) due to the varying length of DNA sequences.
- DNA ligase is crucial for joining small DNA fragments during replication but does not act on both leading and lagging strands simultaneously.
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