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Questions and Answers
What is the main process that converts DNA into RNA?
What type of bond connects nucleotides in a nucleic acid strand?
Which component is NOT found in nucleotides?
In the context of DNA structure, what does 'antiparallel' refer to?
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Which of the following best describes the base-pair complementarity in DNA?
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What is the primary structural form of natural DNA?
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How many base pairs approximately fit into one complete turn of the B form DNA helix?
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Which DNA form has bases that appear to zigzag when viewed from the side?
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Which factor can influence the denaturation of DNA?
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What distinguishes the major groove from the minor groove in B-form DNA?
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Study Notes
Molecular Biology Lecture 1
- Topic: Nucleic Acids, the Genetic Code, and Synthesis of Macromolecules
- Central Dogma: DNA → RNA → Protein
- Transcription: DNA to RNA
- Translation: RNA to protein
- RNA Types: mRNA, rRNA, tRNA
Structure of Nucleic Acids
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Nucleic Acids: Formed by polymerization of nucleotides
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Nucleotides: Composed of a phosphate group, a sugar (ribose or deoxyribose), and a nitrogenous base
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Sugars: Ribose is in RNA, deoxyribose in DNA
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Bases: Purines (Adenine, Guanine) and Pyrimidines (Cytosine, Thymine, Uracil)
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Nucleosides: Base + Sugar
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Nucleotides: Nucleoside + Phosphate
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Phosphodiester Bonds: Link nucleotides in a nucleic acid
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5' End: Phosphate group attached to the 5' carbon
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3' End: Hydroxyl group attached to the 3' carbon
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Directionality: Nucleic acids are synthesized in the 5' to 3' direction
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Nucleotides of DNA: Adenine, guanine, cytosine, thymine.
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nucleotides of RNA: adenine, guanine, cytosine, uracil
Native DNA
- Double Helix: Complementary antiparallel chains
- Base Pairing: G-C, A-T (in DNA), A-U (in RNA)
- Antiparallel Chains: Run in opposite directions (5' to 3' and 3' to 5')
- DNA Forms: B-form (right-handed helix), A-form (right-handed helix, dehydrating), Z-form (left-handed helix)
- Grooves: Major and minor grooves on the outside of the DNA helix
DNA Strand Separation
- Denaturation: DNA unwinding to single strands by high temperature or chemicals (formamide, urea)
- Renaturation: Double-stranded DNA reformed from single strands
- Melting Temperature (Tm): Temperature at which half of the DNA is single-stranded
- G-C Content: Higher G-C content leads to higher Tm (stronger base pairs)
Circular DNA
- Some DNA molecules are circular, i.e. closed loops
RNA Structure and Function
- RNA structure: Varies – secondary structures (stem-loops, hairpins), tertiary
Protein Synthesis
- Proteins: chains of amino acids
- Synthesis of protein: Starts from amino(NH2) and ends at carboxyl (COOH) terminus in proteins and starts at 5' and ends at 3' in nucleic acids
- Modification: Proteins and nucleic acids are often modified after synthesis
Nucleic Acid Synthesis
- Copying: DNA and RNA are made by copying template strands
- Direction: The strands grow in the 5' to 3' direction
- Initiation: RNA polymerase can start strand growth
- DNA polymerase cannot start RNA growth
Organization of Genes
- Prokaryotes: Genes arranged in operons
- Eukaryotes: Genes can be interrupted (exons and introns). mRNA is processed (Introns removed).
RNA in Protein Synthesis
- Messenger RNA (mRNA): Carries genetic code for protein synthesis.
- Transfer RNA (tRNA): Transports amino acids to ribosomes (cloverleaf shape)
- Ribosomes: Protein synthesis takes place on ribosomes (RNA + proteins)
- Genetic Code: 3-letter code (codons) for amino acids. Degenerate, meaning multiple codons can code for the same amino acids
- Aminoacyl-tRNA Synthetases: Enzymes that attach the correct amino acid to the tRNA molecule
- Reading frame: Sequence of codons that specifies the protein sequence.
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Description
Explore the foundational concepts of nucleic acids including their structure, the central dogma of molecular biology, and the process of transcription and translation. Understand the roles of different types of RNA and the significance of nucleotides in the genetic code.
