p.15
Errors in DNA Replication
What can occur when a newly synthesized strand loops out during strand slippage?
The addition of an extra nucleotide base.
p.5
Formation of Dinucleotides and Polynucleotides
In which direction does the condensation reaction proceed during polynucleotide formation?
In the 5' to 3' direction.
p.15
Errors in DNA Replication
What is the error rate of DNA polymerases during replication?
1 error per 100,000 nucleotides.
p.5
Formation of Dinucleotides and Polynucleotides
What directionality does each polynucleotide strand have?
5' to 3' directionality/polarity.
p.14
End Replication Problem
How do prokaryotes differ in terms of the end replication problem?
Prokaryotes do not have an end replication problem because they possess circular DNA.
p.15
Errors in DNA Replication
What happens when the wrong nucleotide is added during DNA replication?
It may not be replaced with the correct nucleotide.
How long-lived is messenger RNA (mRNA)?
Mostly short-lived and degraded once it has been translated.
p.3
Components of Nucleotides
What is a nitrogenous base?
An organic ring structure that is hydrophobic in nature.
What is the composition of ribosomes?
Ribosomes consist of rRNA and ribosomal proteins, forming two subunits.
p.8
Components of Nucleotides
What is located at the 3' end of tRNA?
An amino acid binding site for the specific amino acid.
p.2
Components of Nucleotides
What are the two different pentose sugars involved in nucleotides?
Ribose (for RNA) and deoxyribose (for DNA).
p.8
Structure and Roles of Nucleic Acids
How many different tRNAs are there?
About 45 different tRNAs, each specific to one amino acid.
p.10
Mechanism of DNA Replication
What does DNA polymerase III do during the elongation of the new strand?
It adds free DNA nucleotides to the exposed bases on the parental DNA strand by complementary base pairing.
p.14
End Replication Problem
What is the consequence of the end replication problem?
With each replication, DNA shortens, which may lead to the loss of critical genes after many rounds of replication.
What are the three main types of RNA?
Messenger RNA (mRNA), ribosomal RNA (rRNA), and transfer RNA (tRNA).
p.12
Mechanism of DNA Replication
Why can the lagging-strand polymerase be used repeatedly?
Because it can remain at the fork after finishing the synthesis of each Okazaki fragment.
p.16
Evidence for DNA Replication Mechanisms
What does the conservative hypothesis state about DNA replication?
Both strands act as templates for new DNA, with parental strands re-associating to form one daughter molecule.
p.20
Structure and Roles of Nucleic Acids
How does DNA carry coded information?
Through the sequence of bases that directs cell activity.
p.3
Components of Nucleotides
What type of bonding occurs between nitrogenous bases?
Hydrogen bonds through complementary base pairing.
p.13
Mechanism of DNA Replication
In which direction does DNA polymerase I add new nucleotides?
In the 5’ to 3’ direction.
p.13
Errors in DNA Replication
What problem does DNA polymerase I face with fragment S?
It may encounter a gap if there is no preceding nucleotide to extend from.
p.9
Mechanism of DNA Replication
What role does helicase play in DNA replication?
It breaks hydrogen bonds between complementary bases and unwinds the DNA strands.
p.9
Mechanism of DNA Replication
What stabilizes the single-stranded DNA during replication?
Single-stranded DNA binding proteins.
p.1
Components of Nucleotides
What is the basic structure of a nucleotide?
A nucleotide consists of a sugar, a phosphate group, and a nitrogenous base.
p.19
Mechanism of DNA Replication
What type of DNA was used in the Meselson and Stahl experiment?
DNA labeled with heavy nitrogen (N-15) and light nitrogen (N-14).
p.14
End Replication Problem
What is the end replication problem in eukaryotes?
It occurs when the daughter DNA strand produced is shorter than the parental template strand due to the inability to replace the RNA primer at the 3’ end.
p.14
End Replication Problem
Why does the end replication problem occur?
Because there is no 3’ end available for DNA polymerase to add DNA nucleotides, preventing the replacement of the RNA primer.
p.6
DNA and RNA Structures
What is complementary base pairing in DNA?
A purine always pairs with a pyrimidine; adenine pairs with thymine, and guanine pairs with cytosine.
p.20
Structure and Roles of Nucleic Acids
What is the main role of DNA in living organisms?
DNA is the main storage molecule for genetic information.
p.16
Evidence for DNA Replication Mechanisms
How does the semiconservative hypothesis describe DNA replication?
Both strands separate and serve as templates for new strands, resulting in daughter molecules with one old and one new strand.
p.3
Components of Nucleotides
How are purines and pyrimidines distinguished?
Purines have a two-ring structure, while pyrimidines have a one-ring structure.
p.11
Mechanism of DNA Replication
What role does primase play in the synthesis of Okazaki fragments?
Primase synthesizes primers for each Okazaki fragment.
p.20
Structure and Roles of Nucleic Acids
How does the structure of DNA contribute to its stability?
Hydrophobic interactions between stacked bases and reduced reactivity of nitrogenous bases due to the double helix.
p.11
Mechanism of DNA Replication
What is the function of DNA ligase in DNA replication?
It seals up the gaps between newly replaced DNA and existing fragments by catalyzing the formation of phosphodiester bonds.
p.17
Evidence for DNA Replication Mechanisms
What was the main purpose of Meselson and Stahl's experiment?
To differentiate between original parental DNA and newly synthesized daughter DNA.
p.10
Mechanism of DNA Replication
What is a replicon?
An individual part of a chromosome that replicates as a discrete functional unit.
p.12
Mechanism of DNA Replication
What proteins assist DNA polymerases at the replication fork?
Polymerase accessory proteins, including a sliding clamp and a clamp loader.
p.3
Components of Nucleotides
Where is the phosphate group attached in a nucleotide?
To the 5’ carbon of the pentose sugar.
p.3
Components of Nucleotides
What is the origin of the phosphate group in nucleotides?
It is derived from phosphoric acid.
p.13
Mechanism of DNA Replication
What is a replication bubble?
A structure formed when two replication forks move away from each other.
p.16
Evidence for DNA Replication Mechanisms
What is the dispersive hypothesis in DNA replication?
The parental DNA breaks into segments that act as templates, resulting in daughter strands containing a mix of old and new parts.
p.13
Mechanism of DNA Replication
What are the 5’ and 3’ ends of DNA fragments?
The 5’ end has a phosphate group, and the 3’ end has a hydroxyl group.
p.4
Formation of Dinucleotides and Polynucleotides
What is formed when the two terminal phosphate molecules of a nucleoside triphosphate are hydrolyzed?
A nucleoside monophosphate or nucleotide.
p.22
Discovery of DNA Structure
What recognition did Watson, Crick, and Wilkins receive in 1962?
They jointly received the Nobel Prize in Physiology or Medicine.
p.22
Evidence for DNA Replication Mechanisms
What experiment provided evidence for semiconservative replication of DNA?
Meselson and Stahl’s elegant experiment.
p.10
Errors in DNA Replication
What proofreading capability does DNA polymerase III have?
It can remove incorrectly paired DNA nucleotides and replace them with the correct ones.
p.8
DNA and RNA Structures
What is the stability of DNA compared to RNA?
DNA is chemically stable, while RNA is chemically less stable.
p.1
Semi-Conservative Replication Principles
What is the principle of semi-conservative replication?
In semi-conservative replication, each new DNA molecule consists of one original strand and one newly synthesized strand.
p.19
Mechanism of DNA Replication
What was the main focus of the Meselson and Stahl experiment?
To determine the mechanism of DNA replication.
p.15
Errors in DNA Replication
What is strand slippage in DNA replication?
A process where a newly synthesized strand loops out, causing insertions or deletions of nucleotide bases.
p.19
Semi-Conservative Replication Principles
What did the results of the Meselson and Stahl experiment demonstrate?
That DNA replication is semi-conservative.
p.2
Structure and Roles of Nucleic Acids
What does the central dogma of molecular biology explain?
It explains the directional flow of genetic information.
p.4
Components of Nucleotides
What are nucleotides usually found as in the cytosol?
Nucleoside triphosphates.
p.22
Discovery of DNA Structure
What did Maurice Wilkins and Rosalind Franklin discover through X-ray diffraction in the 1950s?
They detected three primary repeating patterns in the DNA molecule: 0.34nm, 2nm, and 3.4nm.
p.8
Structure and Roles of Nucleic Acids
What is the function of the anticodon in tRNA?
It is complementary to a specific codon on the mRNA.
p.2
Components of Nucleotides
How are the carbon atoms in the pentose sugar numbered?
With a prime (‘) symbol to distinguish them from the carbon atoms at the ring positions of the nitrogenous base.
p.11
Semi-Conservative Replication Principles
What is the end product of DNA replication?
Two daughter DNA molecules, each consisting of one parental strand and one newly synthesized daughter strand.
p.17
Evidence for DNA Replication Mechanisms
What occurred when some bacteria were transferred to a medium containing 14 N?
They synthesized new DNA incorporating the lighter 14 N isotopes.
p.12
Mechanism of DNA Replication
How does the lagging-strand DNA polymerase remain at the fork?
It remains tied to the leading-strand DNA polymerase.
p.12
Mechanism of DNA Replication
What are Okazaki fragments?
Short segments synthesized on the lagging strand during DNA replication.
What is a codon in mRNA?
A sequence of 3 mRNA bases that codes for a certain amino acid.
p.6
DNA and RNA Structures
What is the orientation of the two polynucleotide strands in DNA?
Antiparallel; the 3’ end of one strand is opposite the 5’ end of the other.
p.22
Discovery of DNA Structure
Who constructed the first accurate model of the DNA molecule?
James Watson and Francis Crick.
p.22
Discovery of DNA Structure
What ongoing debate exists regarding the discovery of DNA structure?
Debate continues on who should receive credit for the discovery.
p.20
Mechanism of DNA Replication
What is semi-conservative replication?
A process where each original DNA strand serves as a template for a new strand.
p.8
DNA and RNA Structures
How many polynucleotide chains does RNA have?
Single polynucleotide chain.
p.8
DNA and RNA Structures
What is the lifespan of mRNA?
Maybe temporary, as it is degraded once translated.
p.5
Formation of Dinucleotides and Polynucleotides
What group is found at the 3' end of a polynucleotide strand?
A free hydroxyl (-OH) group attached to the 3' carbon of the pentose sugar.
p.15
Errors in DNA Replication
What can happen to the template strand during strand slippage?
It may loop out, resulting in the deletion of a nucleotide base in the newly synthesized strand.
p.19
Semi-Conservative Replication Principles
What is the significance of the term 'semi-conservative' in DNA replication?
Each new DNA molecule consists of one original strand and one newly synthesized strand.
p.12
Mechanism of DNA Replication
What is the role of DNA polymerase at the replication fork?
Two DNA polymerase molecules are active at the fork at any one time.
What is the typical structure of most RNA molecules?
Most RNA molecules are single-stranded.
p.14
End Replication Problem
What role do telomeres play in relation to the end replication problem?
Telomeres help protect chromosomes from shortening during replication, which is linked to the end replication problem.
p.21
Discovery of DNA Structure
What did the discovery of DNA demonstrate about the Nature & Practices of Science?
It showed many features of scientific inquiry in action.
p.6
DNA and RNA Structures
How are the two strands of DNA held together?
By hydrogen bonds between nitrogenous bases.
p.13
Mechanism of DNA Replication
What are the two types of strands in a replication fork?
Leading strand and lagging strand.
p.2
Mechanism of DNA Replication
What processes are involved in the transmission of genetic information?
DNA replication, transcription, and translation.
p.9
Semi-Conservative Replication Principles
What must a molecule capable of acting as genetic material do?
Code for and store genetic information, and replicate accurately.
p.8
Structure and Roles of Nucleic Acids
What shape does tRNA fold into?
A characteristic 'clover-leaf' shape.
p.8
Components of Nucleotides
What is the sequence at the 5' and 3' ends of tRNA?
5' end always ends in G and 3' end always ends in CCA.
p.9
Evidence for DNA Replication Mechanisms
What experimental work supported Watson and Crick's hypothesis on DNA replication?
The work by Meselson and Stahl.
What is the structure of ribosomal RNA (rRNA)?
It is single-stranded but may fold into different shapes.
p.20
Structure and Roles of Nucleic Acids
What is the significance of the number of hydrogen bonds in DNA?
They provide stability, allowing heritable changes to occur rarely.
p.10
Mechanism of DNA Replication
What is the role of primase in DNA replication?
Primase catalyzes the synthesis of an RNA primer complementary to DNA nucleotides on the template.
p.10
Mechanism of DNA Replication
Why can't DNA polymerase III initiate DNA synthesis?
It cannot synthesize DNA from scratch; it can only add new nucleotides to a pre-existing 3' hydroxyl (-OH) end provided by RNA primers.
p.8
Structure and Roles of Nucleic Acids
What is the main function of tRNA?
To bring the appropriate amino acid to the ribosome for protein synthesis.
p.10
Mechanism of DNA Replication
In which direction does DNA polymerase III work?
In the 5' to 3' direction with respect to the growing chain.
p.11
Mechanism of DNA Replication
What happens to RNA primers after the synthesis of DNA?
They are removed and replaced with corresponding DNA nucleotides by DNA polymerase I.
p.6
DNA and RNA Structures
What is the structure of a DNA molecule?
DNA is double-stranded, made up of two polynucleotide strands.
p.2
Structure and Roles of Nucleic Acids
What is the role of nucleic acids in living organisms?
Nucleic acids, like proteins, are essential for life and DNA forms the genetic material of all living organisms.
p.4
Formation of Dinucleotides and Polynucleotides
What happens to two molecules of water during nucleotide formation?
They are removed in the process.
Where is ribosomal RNA (rRNA) synthesized?
In the nucleolus region of the nucleus.
p.11
Mechanism of DNA Replication
In which direction does DNA polymerase III elongate the leading strand?
In the 5’ to 3’ direction.
p.6
DNA and RNA Structures
What are the two types of grooves found in the DNA double helix?
Major groove and minor groove.
p.11
Mechanism of DNA Replication
How does DNA polymerase III move during the synthesis of Okazaki fragments?
It moves along the template away from the replication fork.
p.4
Formation of Dinucleotides and Polynucleotides
What is located at one end of a polynucleotide?
A free phosphate group (5' end).
p.20
Errors in DNA Replication
How does DNA repair occur?
Using the intact complementary strand as a template to guide the repair.
p.17
Evidence for DNA Replication Mechanisms
How were DNA samples separated in the Meselson and Stahl experiment?
Using ultracentrifugation based on different densities.
What allows regions of RNA to loop back upon itself?
Complementary base pairing.
p.6
DNA and RNA Structures
What is the shape of the DNA structure?
A double helical structure.
p.16
Evidence for DNA Replication Mechanisms
What are the three hypotheses proposed for DNA replication?
Conservative, dispersive, and semiconservative mechanisms.
p.16
Evidence for DNA Replication Mechanisms
Who conducted the experiment in 1958 to prove the semiconservative mechanism of DNA replication?
Matthew Meselson and Franklin Stahl.
p.22
Discovery of DNA Structure
What did Erwin Chargaff's analysis of DNA reveal in the 1940s?
That DNA from any cell of all organisms has a 1:1 ratio of pyrimidine and purine bases, specifically that cytosine equals guanine and adenine equals thymine.
p.2
Components of Nucleotides
What are nucleotides?
Monomers that make up nucleic acids, arranged to form long molecules called polynucleotides.
p.20
Structure and Roles of Nucleic Acids
Why is DNA able to store large amounts of genetic information?
Because it is a long polymer with a linear sequence of bases.
p.11
Mechanism of DNA Replication
What are Okazaki fragments?
Short fragments of nucleotides synthesized discontinuously on the lagging strand.
p.20
Structure and Roles of Nucleic Acids
What role do phosphodiester bonds play in DNA?
They strengthen the strands of DNA nucleotides.
p.9
Mechanism of DNA Replication
Where does DNA replication begin?
At a site known as the origin of replication.
p.1
Relating the Structure of DNA to its Function
What is the significance of the structure of DNA?
The structure of DNA allows it to store genetic information and facilitate replication.
p.16
Evidence for DNA Replication Mechanisms
What hypothesis did Watson and Crick propose regarding DNA replication?
The semiconservative mechanism.
What is the function of messenger RNA (mRNA)?
Carries information from DNA out of the nucleus to ribosomes in the cytoplasm.
p.2
Structure and Roles of Nucleic Acids
What are the two types of nucleic acids?
Deoxyribonucleic acid (DNA) and ribonucleic acid (RNA).
p.10
Mechanism of DNA Replication
What is the origin of replication in prokaryotes?
There is only one origin of replication where DNA replication initiates.
p.2
Components of Nucleotides
What are the three components of a nucleotide?
Pentose sugar, inorganic phosphate, and nitrogenous base.
p.9
Mechanism of DNA Replication
What happens during the unwinding and separation of DNA strands?
Each unwound strand acts as a template for synthesizing a new daughter strand.
p.9
Semi-Conservative Replication Principles
What is produced as a result of semi-conservative replication?
Two daughter DNA molecules, each containing one parental and one newly synthesized strand.
p.20
Mechanism of DNA Replication
What is the process of DNA replication?
DNA strands base pair to create copies without loss of information.
p.4
Formation of Dinucleotides and Polynucleotides
How are nucleotides linked together in a polynucleotide?
Via phosphodiester bonds between the 5’ and 3’ carbons of the pentose sugars.
p.17
Evidence for DNA Replication Mechanisms
Who performed the experiments that supported the semi-conservative replication hypothesis?
Meselson and Stahl in 1958.
p.17
Evidence for DNA Replication Mechanisms
What happened to the DNA of E. coli after 14 generations in the 15 N medium?
All bases in the DNA incorporated the 15 N element, making it heavier than normal DNA.
p.1
DNA and RNA Structures
What are the differences between DNA and RNA?
DNA is double-stranded and contains deoxyribose sugar, while RNA is single-stranded and contains ribose sugar.
p.11
Semi-Conservative Replication Principles
What is the overall direction of replication for both strands?
Towards the replication fork.
p.20
Errors in DNA Replication
What is the significance of mutations in DNA?
They can lead to new stable forms of a gene, contributing to genetic variation.
p.10
Mechanism of DNA Replication
What is the function of the phosphodiester bond in DNA replication?
It links two adjacent DNA nucleotides together.
p.9
Mechanism of DNA Replication
What is formed as the two DNA strands separate?
A replication bubble with a replication fork at each end.
p.11
Semi-Conservative Replication Principles
What is the mechanism of DNA replication called?
Semi-conservative replication.
p.8
DNA and RNA Structures
How many polynucleotide chains does DNA have?
Double nucleotide chains forming a double helix.
p.9
Mechanism of DNA Replication
What is a replication fork?
A Y-shaped structure formed when the double-stranded DNA unwinds to expose single-stranded templates.
p.17
Evidence for DNA Replication Mechanisms
What was the initial medium used to culture E. coli in the experiment?
A nutrient medium containing the heavy isotope of nitrogen, 15 N.
p.1
Mechanism of DNA Replication
What is the process of DNA replication?
DNA replication is the process by which a DNA molecule makes a copy of itself.
p.1
End Replication Problem
What is the end replication problem?
The end replication problem arises because DNA polymerase cannot fully replicate the ends of linear chromosomes.
p.17
Evidence for DNA Replication Mechanisms
What did the relative position of DNA bands in the centrifuge tubes indicate?
They supported the semi-conservative mode of DNA replication.
p.18
Evidence for DNA Replication Mechanisms
What was observed in Generation 2 of the experiment?
Two bands of equal thickness: one of the intermediate type and one of the light density type (50% 15N 14N, 50% 14N 14N).
p.1
Evidence for DNA Replication Mechanisms
What evidence supports the semi-conservative replication of DNA?
Experiments such as those by Meselson and Stahl provide evidence for semi-conservative replication.
p.18
Evidence for DNA Replication Mechanisms
What was the condition for Generation 1 in Meselson and Stahl's experiment?
Grown in 14N for 1 generation.
p.18
Evidence for DNA Replication Mechanisms
What was observed in Generation 1 of the experiment?
One band, all of the intermediate density type (100% 15N 14N).
p.1
Formation of Dinucleotides and Polynucleotides
What are dinucleotides and polynucleotides?
Dinucleotides are formed from two nucleotides, while polynucleotides are long chains of nucleotides, such as DNA and RNA.
p.18
Evidence for DNA Replication Mechanisms
What was observed in Generation 0 of the experiment?
One band, all of the heavy type (100% 15N 15N).
p.18
Evidence for DNA Replication Mechanisms
What was the condition for Generation 0 in Meselson and Stahl's experiment?
Grown in 15N for 14 generations.
p.18
Evidence for DNA Replication Mechanisms
What was the condition for Generation 2 in Meselson and Stahl's experiment?
Grown in 14N for 2 generations.
