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Questions and Answers
What is a primary structural feature of tRNA?
What is a primary structural feature of tRNA?
What percentage of total RNA in a cell is made up of ribosomal RNA (rRNA)?
What percentage of total RNA in a cell is made up of ribosomal RNA (rRNA)?
What is a key role of small nuclear RNA (SnRNA) in eukaryotic cells?
What is a key role of small nuclear RNA (SnRNA) in eukaryotic cells?
Which of the following statements correctly describes the differences between RNA and DNA?
Which of the following statements correctly describes the differences between RNA and DNA?
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What distinguishes ribosomal RNA (rRNA) from other types of RNA?
What distinguishes ribosomal RNA (rRNA) from other types of RNA?
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What is the primary factor that determines the melting temperature of DNA?
What is the primary factor that determines the melting temperature of DNA?
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During denaturation, which of the following events occurs?
During denaturation, which of the following events occurs?
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Which of the following accurately describes a key difference between prokaryotic and eukaryotic DNA?
Which of the following accurately describes a key difference between prokaryotic and eukaryotic DNA?
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What is the primary role of ribonucleic acid (RNA) within the cell?
What is the primary role of ribonucleic acid (RNA) within the cell?
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Which type of RNA carries the genetic code from DNA to the ribosome?
Which type of RNA carries the genetic code from DNA to the ribosome?
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What is the process of renaturation in nucleic acids?
What is the process of renaturation in nucleic acids?
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Which of the following statements about the structure of RNA is accurate?
Which of the following statements about the structure of RNA is accurate?
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What type of bond links nucleotides together in a nucleic acid chain?
What type of bond links nucleotides together in a nucleic acid chain?
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What is the main difference between prokaryotic and eukaryotic DNA regarding structure?
What is the main difference between prokaryotic and eukaryotic DNA regarding structure?
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Which of the following accurately describes messenger RNA (mRNA) in eukaryotic organisms?
Which of the following accurately describes messenger RNA (mRNA) in eukaryotic organisms?
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What is the primary function of transfer RNA (tRNA)?
What is the primary function of transfer RNA (tRNA)?
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How do prokaryotic and eukaryotic mRNA differ in terms of their coding capacity?
How do prokaryotic and eukaryotic mRNA differ in terms of their coding capacity?
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Which of the following statements about RNA structure is true?
Which of the following statements about RNA structure is true?
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What role does ribosomal RNA (rRNA) play in protein synthesis?
What role does ribosomal RNA (rRNA) play in protein synthesis?
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What is the highest level of structure that RNA can achieve?
What is the highest level of structure that RNA can achieve?
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What is a distinguishing feature of prokaryotic DNA concerning plasmids?
What is a distinguishing feature of prokaryotic DNA concerning plasmids?
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Study Notes
DNA and RNA Chemical Structure
- Nucleic acids are the principle information molecules in cells, carrying all genetic codes.
- Nucleic acids are linear polymers of nucleotides.
- DNA and RNA are two types of nucleic acids.
Types of Nucleic Acids
-
Deoxyribonucleic Acid (DNA):
- Pentose sugar is deoxyribose (lacks an oxygen atom at the 2' position).
- Bases: Purines (Adenine, Guanine) and Pyrimidines (Cytosine, Thymine).
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Ribonucleic Acid (RNA):
- Pentose sugar is ribose.
- Bases: Purines (Adenine, Guanine) and Pyrimidines (Cytosine, Uracil).
Base Pairing
- DNA strands are antiparallel.
- Bases pair via hydrogen bonds:
- Adenine pairs with Thymine (2 hydrogen bonds).
- Guanine pairs with Cytosine (3 hydrogen bonds).
Nucleotide Structure
- Nucleotides are composed of a nitrogenous base, a pentose sugar, and one or more phosphate groups.
- A nucleoside is a nitrogenous base and a sugar linked together.
- A nucleotide is a nucleoside and a phosphate group.
- Nucleotides polymerize to form nucleic acids.
- Polynucleotide chains are synthesized in the 5' to 3' direction.
DNA Duplex
- Two antiparallel DNA strands are interconnected by hydrogen bonds between purine and pyrimidine bases.
DNA Structure
- DNA's double helix forms a right-handed helix.
- A complete turn of the helix is 3.4 nm long.
- The distance between adjacent bases is 0.34 nm.
- A turn contains 10 base pairs.
- The helix contains a major groove and a minor groove.
Forms of DNA
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B-form:
- Most common form in cells
- Right-handed helix
- Turn every 3.4 nm
- 10 base pairs per turn
- Contains a major and minor groove
-
A-form:
- Less common than B-form
- Right-handed helix
- Turn every 2.82 nm
- 11 base pairs per turn
-
Z-form:
- Less common form
- Left-handed helix
- Turn every 4.56 nm
- 12 base pairs per turn
- Radical change of B-form, GC-rich DNA regions.
- The sugar-base backbone forms a zig-zag shape.
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Properties of B-DNA, A-DNA, and Z-DNA are summarized in a table.
Denaturation and Annealing of DNA
- Denaturation is the loss of helical structure in DNA due to heat or chemicals.
- AT regions denature first (2 H bonds).
- GC regions denature last (3 H bonds).
- Denaturation is reversible, and strands can re-anneal when cooled.
- Melting temperature (Tm) is the temperature at which half of the DNA becomes single-stranded.
Hyperchromicity
- Hyperchromicity (melting profile) is used to measure DNA denaturation.
- Single-stranded (ss) DNA absorbs more UV light than double-stranded (ds) DNA at 260 nm.
- The melting profile shows a change in absorption versus temperature.
- A-T rich regions denature first.
- G-C rich regions denature last.
Comparison between Prokaryotic and Eukaryotic DNA
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Prokaryotic DNA:
- Main chromosome is circular.
- DNA is naked.
- DNA is free within the cell.
- No introns.
- Plasmid is present.
-
Eukaryotic DNA:
- Each chromosome is linear.
- DNA is linked with histone proteins.
- DNA is enclosed within the nucleus.
- Introns are present.
- Plasmid is absent.
RNA Structure
- RNA is a single-stranded polynucleotide molecule.
- It can have three levels of structure:
- Primary: Nucleotide sequence.
- Secondary: Hairpin loops (base pairing).
- Tertiary: Motifs and 3D folding.
RNA Function
- RNA retrieves protein code from DNA and carries out the needed processes to produce proteins.
- RNA is found inside and outside the nucleus (e.g., nucleus, ribosome, mitochondria, cytoplasm).
Classes of RNA
-
Messenger RNA (mRNA):
- Carries genetic information from DNA in the form of a series of 3-base codes (codons).
- Synthesized in the nucleus during transcription and relocated to the cytoplasm.
-
Transfer RNA (tRNA):
- Smallest of major RNA types.
- Adapter to read mRNA code and deliver amino acids to ribosomes.
-
Ribosomal RNA (rRNA):
- Major component of ribosomes, which are essential for protein synthesis.
-
Small RNAs: e.g., small nuclear RNA (snRNA), microRNA (miRNA).
- Involved in mRNA processing and gene regulation.
RNA vs. DNA
- Key differences in structure and function between RNA and DNA are summarized in tables. RNA and DNA also have different sugar molecules.
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Description
Explore the chemical structures of DNA and RNA through this quiz. Understand the components of nucleic acids, their types, and the essential base pairing mechanisms. Test your knowledge on how these fundamental molecules carry genetic information.
