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Questions and Answers
What role do enzymes play in cell activities?
What role do enzymes play in cell activities?
What occurs during transcription?
What occurs during transcription?
Which process involves the joining of tRNA and codons?
Which process involves the joining of tRNA and codons?
What is the significance of a non-overlapping code in genetics?
What is the significance of a non-overlapping code in genetics?
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How many amino acids are encoded by a polypeptide chain consisting of 438 DNA bases?
How many amino acids are encoded by a polypeptide chain consisting of 438 DNA bases?
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What are the components of a nucleotide?
What are the components of a nucleotide?
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Which statement about the structure of DNA is correct?
Which statement about the structure of DNA is correct?
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Which of the following represents Chargaff's rules?
Which of the following represents Chargaff's rules?
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What is the difference between DNA and RNA in terms of sugar?
What is the difference between DNA and RNA in terms of sugar?
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Which type of RNA is primarily involved in protein synthesis?
Which type of RNA is primarily involved in protein synthesis?
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What is characteristic of the DNA double helix structure?
What is characteristic of the DNA double helix structure?
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What distinguishes uracil in RNA from thymine in DNA?
What distinguishes uracil in RNA from thymine in DNA?
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What type of bond links the sugar-phosphate backbone in DNA?
What type of bond links the sugar-phosphate backbone in DNA?
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What structure is formed by tRNA?
What structure is formed by tRNA?
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What does the term 'semi-conservative model' refer to in DNA replication?
What does the term 'semi-conservative model' refer to in DNA replication?
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What is the primary role of mRNA in protein synthesis?
What is the primary role of mRNA in protein synthesis?
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Which of the following correctly describes the role of mRNA in protein synthesis?
Which of the following correctly describes the role of mRNA in protein synthesis?
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During which stage of protein synthesis does RNA polymerase catalyze the formation of mRNA?
During which stage of protein synthesis does RNA polymerase catalyze the formation of mRNA?
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What is indicated by the term 'degenerate code' in genetic coding?
What is indicated by the term 'degenerate code' in genetic coding?
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What happens to mRNA after protein synthesis is complete?
What happens to mRNA after protein synthesis is complete?
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Which process describes the flow of genetic information from DNA to protein?
Which process describes the flow of genetic information from DNA to protein?
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How many amino acids can a duplet code realistically specify?
How many amino acids can a duplet code realistically specify?
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Which of the following correctly describes the function of tRNA in translation?
Which of the following correctly describes the function of tRNA in translation?
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What is the primary site of rRNA synthesis within the cell?
What is the primary site of rRNA synthesis within the cell?
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What is the first step in the process of protein synthesis?
What is the first step in the process of protein synthesis?
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In terms of genetic information flow, which statement is correct?
In terms of genetic information flow, which statement is correct?
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How is the genetic code described in terms of the universality among organisms?
How is the genetic code described in terms of the universality among organisms?
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What is the role of the ribosome during protein synthesis?
What is the role of the ribosome during protein synthesis?
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What determines the primary structure of a protein?
What determines the primary structure of a protein?
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Study Notes
DNA Structure and Replication
- DNA is a double helix, 3.4 nm per full turn, 10 base pairs per turn, base pair ~0.34 nm
- Two strands are anti-parallel
- A=T; G=C, hydrogen bonds, complementary base pairing
- Radius = 1 nm
- Sugar-phosphate backbone linked by phosphodiester bonds
- Nucleotides consist of a pentose sugar (ribose/deoxyribose), a nitrogenous base, and a phosphate group
- DNA molecule binds with histones, forming nucleosomes, which condense further into chromatin fibers, ultimately forming chromosomes
- DNA replication is semi-conservative, resulting in two new DNA strands that are exact replicas of the parent strand
Nucleic Acids
- Monomers are nucleotides
- Functions include storage and transmission of genetic information, structural or catalytic roles
- Two types found in living organisms: Deoxyribonucleic acid (DNA) and Ribonucleic acid (RNA)
Structure of RNA
- Similar to DNA, but uracil replaces thymine and ribose replaces deoxyribose
- Single polynucleotide chain
- Three types of RNA:
- Messenger RNA (mRNA)
- Transfer RNA (tRNA)
- Ribosomal RNA (rRNA)
DNA Replication
- Base pairing allows existing DNA strands to serve as templates for new complementary strands.
- When a cell copies DNA, the two strands unwind/untwist, each serving as a template
- Enzymes link nucleotides to form a new strand.
- Creates two DNA strands (exact copies of parent), following the semi-conservative model
Protein Synthesis
- A polypeptide is coded for by a gene, which is a sequence of nucleotides in a DNA molecule.
- DNA's information is used during transcription and translation
- mRNA, tRNA, and ribosomes play crucial roles
- Transcription: synthesis of mRNA under DNA's direction. Non-coding strand of DNA serves as a template for mRNA. Free RNA nucleotides attach to the template (catalyzed by RNA polymerase).
- Translation: actual synthesis of a polypeptide. Occurs under the direction of mRNA. mRNA base sequence is translated into amino acid sequence of a polypeptide. Stages include: mRNA carrying information to ribosomes, amino acid activation, translation, and functional protein production.
The Central Dogma of Molecular Biology
- First expressed by Francis Crick
- Detailed transfer of sequential information
- Genetic information flows from DNA into protein, but not back
Genetic Code
- Triplet code: genetic instructions for a polypeptide chain are written in DNA as 3-nucleotide words
- DNA stores information as sequences of bases
- The genetic code is degenerate (more than one codon can code for the same amino acid)
- Non-overlapping code: each DNA base only contributes to coding for one amino acid
- Universal code: the DNA base triplets code for the same amino acids in all organisms.
Transcription and Translation
- Transcription produces mRNA (RNA synthesis under DNA's direction), unique sequence of RNA nucleotide. mRNA serves as genetic message.
- Translation is the actual synthesis of a polypeptide. Changes language(nucleotide → amino acid). Translation occurs under the direction of mRNA
- Both nucleic acids have the same language.
Stages of Protein Synthesis
- Stage 1: Transcription DNA unwinds, hydrogen bonds break, forming mRNA using DNA's non-coding strand. Free RNA nucleotides attach to the template DNA
- Stage 2: mRNA carries information to ribosomes mRNA exits nucleus and enters cytoplasm
- Stage 3: Amino Acid Activation tRNA molecules carry specific amino acids
- Stage 4: Translation Each mRNA codon attracts a tRNA with the complementary anticodon. Peptide bonds form between amino acids. tRNA detaches and leaves ribosome, mRNA eventually degrades.
- Stage 5: Functional Protein Produced Completed polypeptide processed by cellular machinery to create final functional protein (e.g., enzyme).
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Description
Test your knowledge on the structure and replication of DNA and the characteristics of RNA. This quiz covers key concepts such as base pairing, nucleotides, and the roles of nucleic acids in genetic information storage and transmission. Perfect for students studying molecular biology.
