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The DNA double helix exhibits a pitch of approximately 3.4 nanometers and a radius of about 1.0 nanometer.
Answer: True
The DNA double helix is characterized by specific dimensions, including a pitch of approximately 3.4 nm and a radius of about 1.0 nm.
Single-stranded DNA (ssDNA) is formed when the two strands of double-stranded DNA (dsDNA) separate, a process often induced by elevated temperatures or alterations in pH.
Answer: True
Single-stranded DNA (ssDNA) arises from the dissociation of the two complementary strands of dsDNA, a phenomenon commonly triggered by factors such as high temperatures or changes in pH.
The DNA double helix is characterized by two antiparallel polynucleotide chains that are coiled around a common axis.
Answer: True
The canonical structure of DNA is a double helix formed by two polynucleotide strands oriented in opposite directions (antiparallel) and wound around the same central axis.
Hydrogen bonds between complementary base pairs and base-stacking interactions are the primary forces responsible for stabilizing the DNA double helix.
Answer: True
The structural integrity of the DNA double helix is maintained through a combination of hydrogen bonds connecting the complementary bases (A-T and G-C) and van der Waals forces contributing to base-stacking interactions.
The major groove of the DNA double helix is important because it offers greater accessibility for proteins to interact with the edges of the base pairs.
Answer: True
The major groove provides a more extensive surface for protein binding compared to the minor groove, facilitating sequence-specific recognition of DNA by regulatory proteins.
DNA is typically a double helix, utilizes deoxyribose sugar, and comprises the bases Adenine, Guanine, Cytosine, and Thymine.
Answer: True
The fundamental characteristics of DNA include its double helical structure, the presence of deoxyribose sugar in its backbone, and the four nitrogenous bases: Adenine, Guanine, Cytosine, and Thymine.
Adenine pairs with Guanine, and Cytosine pairs with Thymine in DNA.
Answer: False
In DNA, Adenine (A) pairs with Thymine (T) via two hydrogen bonds, and Guanine (G) pairs with Cytosine (C) via three hydrogen bonds.
The two strands of DNA are held together by covalent bonds between the complementary nitrogenous bases.
Answer: False
The two DNA strands are held together by hydrogen bonds between complementary base pairs and by base-stacking interactions, not covalent bonds.
The DNA double helix is primarily stabilized by covalent bonds between base pairs and hydrophobic interactions.
Answer: False
The DNA double helix is primarily stabilized by hydrogen bonds between complementary base pairs and by base-stacking interactions, not covalent bonds or hydrophobic interactions.
The minor groove of the DNA double helix is the primary site where proteins recognize and bind to specific DNA sequences due to its wider accessibility.
Answer: False
The major groove, not the minor groove, is the primary site for protein recognition and binding due to its greater accessibility to the base edges.
DNA stability is influenced by its GC-content, sequence, and length, with higher GC-content generally leading to less stable DNA.
Answer: False
Higher GC-content generally leads to *more* stable DNA due to the three hydrogen bonds between G-C pairs compared to the two in A-T pairs.
Which nitrogenous base pairs with Adenine (A) in DNA?
Answer: Thymine (T)
How are the two strands of the DNA double helix primarily held together?
Answer: Hydrogen bonds between the complementary nitrogenous bases.
What is the approximate pitch of the DNA double helix?
Answer: 3.4 nanometers
Which of the following are the two main forces that stabilize the DNA double helix?
Answer: Hydrogen bonds and base-stacking interactions.
What is the significance of the major groove in the DNA double helix?
Answer: It provides greater accessibility for proteins to recognize and bind specific DNA sequences.
What gives DNA its acidic properties?
Answer: The phosphate groups
DNA is a polymer composed of amino acids that coil around each other to form a double helix.
Answer: False
DNA is a polymer composed of nucleotides, not amino acids. Amino acids are the building blocks of proteins.
The four major types of macromolecules essential for all known forms of life include DNA, proteins, lipids, and monosaccharides.
Answer: False
The four major types of macromolecules are nucleic acids, proteins, lipids, and carbohydrates (polysaccharides). Monosaccharides are simple sugars, not the macromolecule class.
The four nitrogenous bases found in DNA are Adenine, Guanine, Cytosine, and Uracil.
Answer: False
DNA contains the nitrogenous bases Adenine, Guanine, Cytosine, and Thymine. Uracil is found in RNA, replacing Thymine.
Purines, like Cytosine and Thymine, consist of fused five- and six-membered heterocyclic rings.
Answer: False
Purines (Adenine and Guanine) consist of fused rings. Cytosine and Thymine are pyrimidines, which are single six-membered rings.
DNA and RNA are identical in their sugar component, both using deoxyribose.
Answer: False
DNA uses deoxyribose sugar, while RNA uses ribose sugar.
Which of the following is NOT one of the four major types of macromolecules essential for all known forms of life?
Answer: Vitamins
What are the repeating monomeric units that make up DNA?
Answer: Nucleotides
Which pair of bases consists of purines?
Answer: Adenine and Guanine
What is a key difference between DNA and RNA mentioned in the source?
Answer: DNA uses deoxyribose sugar, while RNA uses ribose sugar and replaces Thymine with Uracil.
DNA ligase is essential for DNA repair, catalyzing the formation of phosphodiester bonds to seal breaks in the DNA backbone.
Answer: True
DNA ligase functions to join DNA fragments by forming phosphodiester bonds, a critical step in DNA repair pathways and replication.
DNA polymerases are enzymes responsible for synthesizing new DNA strands by adding nucleotides according to a template strand.
Answer: True
DNA polymerases are the primary enzymes involved in DNA replication, extending a primer by incorporating complementary nucleotides onto a template strand.
Transcription factors are proteins that bind to specific DNA sequences to modulate the transcription of genes.
Answer: True
Transcription factors are regulatory proteins that control gene expression by binding to specific DNA elements, thereby influencing the rate of transcription initiation.
The central dogma of molecular biology, proposed by Watson and Crick, describes the flow of information from RNA to DNA to protein.
Answer: False
The central dogma describes the flow of genetic information from DNA to RNA to protein.
Transcription is the process where the sequence of messenger RNA (mRNA) is decoded by ribosomes to synthesize a protein.
Answer: False
The process of decoding mRNA by ribosomes to synthesize protein is called translation, not transcription.
Restriction enzymes cut DNA at random sequences, making them useful for general DNA fragmentation.
Answer: False
Restriction enzymes cut DNA at specific recognition sequences, not random ones.
The 'central dogma of molecular biology' describes the flow of genetic information from:
Answer: DNA to RNA to Protein
Which enzyme is responsible for synthesizing new DNA strands by adding nucleotides?
Answer: DNA polymerase
What is the function of topoisomerases in DNA management?
Answer: To manage the supercoiling of DNA by cutting and rejoining strands.
The process where the genetic information encoded in DNA is copied into a complementary messenger RNA (mRNA) sequence is called:
Answer: Transcription
What are Okazaki fragments?
Answer: Short segments of DNA synthesized discontinuously on the lagging strand.
What is the function of helicases in DNA processes?
Answer: To unwind the DNA double helix using ATP hydrolysis.
What is the role of restriction enzymes in molecular biology?
Answer: They cut DNA strands at specific recognition sequences.
Histones are proteins that facilitate the compaction of DNA within the nucleus by wrapping around it to form nucleosomes.
Answer: True
Histones are fundamental to DNA packaging in eukaryotes, serving as spools around which DNA winds to create nucleosomes, thereby compacting the genetic material.
In eukaryotic cells, DNA is primarily found in circular chromosomes within the cytoplasm.
Answer: False
In eukaryotic cells, DNA is primarily organized into linear chromosomes within the nucleus. Circular chromosomes are characteristic of prokaryotic cells.
Where is DNA primarily organized in eukaryotic cells?
Answer: Primarily within the cell nucleus, organized into linear chromosomes.
What are telomeres?
Answer: Specialized regions of DNA found at the ends of linear chromosomes.
What is the primary role of histones in eukaryotic cells?
Answer: To package DNA by wrapping it to form nucleosomes.
Rosalind Franklin's X-ray diffraction images, notably 'Photo 51', were instrumental in establishing the helical structure of DNA.
Answer: True
Rosalind Franklin's pioneering X-ray diffraction studies provided crucial data, including the helical nature and dimensions of DNA, which were essential for elucidating its structure.
The Avery-MacLeod-McCarty experiment identified DNA as the 'transforming principle', providing evidence that DNA carries genetic information.
Answer: True
The landmark Avery-MacLeod-McCarty experiment demonstrated that DNA, not protein, functions as the carrier of genetic information, a concept termed the 'transforming principle'.
The Avery-MacLeod-McCarty experiment in 1944 provided strong evidence that protein, rather than DNA, carries genetic information.
Answer: False
The Avery-MacLeod-McCarty experiment provided strong evidence that DNA, not protein, carries genetic information.
Who first isolated DNA and called it 'nuclein'?
Answer: Friedrich Miescher
The Avery-MacLeod-McCarty experiment provided strong evidence for which concept?
Answer: DNA, not protein, carries genetic information.
Chargaff's rules are crucial for understanding DNA structure because they state:
Answer: The amount of Adenine equals Thymine, and Guanine equals Cytosine.
What key contribution did Rosalind Franklin make to understanding DNA's structure?
Answer: She produced X-ray diffraction images providing data on DNA's helical nature.
What is the significance of the Meselson-Stahl experiment?
Answer: It provided final confirmation of the semi-conservative replication mechanism for DNA.
What was identified as the 'transforming principle' by Avery, MacLeod, and McCarty?
Answer: DNA
Comparative analysis of DNA sequences among organisms aids scientists in elucidating their evolutionary relationships and reconstructing population histories.
Answer: True
DNA sequences serve as a molecular record of evolutionary history. By comparing these sequences, scientists can infer phylogenetic relationships and understand past population dynamics.
5-methylcytosine, a modified base, plays a significant role in the epigenetic regulation of gene expression.
Answer: True
The presence of 5-methylcytosine, a non-canonical DNA base, is a key epigenetic modification that influences gene activity by altering chromatin structure and gene silencing.
DNA nanotechnology employs DNA as a building material to construct intricate molecular architectures and devices.
Answer: True
DNA nanotechnology leverages the self-assembly properties of DNA to create nanoscale structures and functional devices, utilizing DNA as a programmable material.
In humans, approximately 50% of DNA is non-coding, meaning these sections do not serve as templates for protein sequences.
Answer: False
In humans, more than 98% of DNA is non-coding. The extensive non-coding regions contribute to the 'C-value enigma,' where genome size does not correlate with organismal complexity.
The 'C-value enigma' suggests that larger genome sizes always correlate with greater organismal complexity.
Answer: False
The 'C-value enigma' refers to the lack of correlation between genome size and organismal complexity or gene number.
What is the primary function of Deoxyribonucleic Acid (DNA)?
Answer: To serve as the carrier of genetic instructions for development, functioning, and reproduction.
What percentage of human DNA is considered non-coding?
Answer: More than 98%
DNAzymes, or catalytic DNA, are significant because they:
Answer: Can catalyze various chemical reactions, enhancing reaction rates.
How does DNA store genetic information?
Answer: In the specific sequence of the four nucleotide bases along the backbone.
What is a potential function of Extracellular DNA (eDNA)?
Answer: To facilitate horizontal gene transfer and act as a nutrient source.
In DNA profiling (DNA fingerprinting), which sections of DNA are typically compared?
Answer: Variable sections of repetitive DNA, such as short tandem repeats.
The 'C-value enigma' refers to the lack of correlation between:
Answer: Genome size (C-value) and organismal complexity or gene number.
DNA intercalators affect DNA by:
Answer: Fitting between base pairs, distorting the helix and inhibiting processes.
How does DNA methylation typically influence gene expression?
Answer: It is associated with regions of DNA that have low or no gene expression.
What are aptamers?
Answer: Synthetic oligonucleotide ligands selected to bind specific target molecules.