Nucleic Acids Overview
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Questions and Answers

What is the significance of the triplet groups along the mRNA strand in protein synthesis?

The triplet groups specify particular amino acids, dictating the sequence of amino acids in the protein.

Why is the process of translation referred to as converting information from one language to another?

Translation converts genetic information from the linear sequence of nucleotides in mRNA into a linear sequence of amino acids in proteins.

What is the role of aminoacyl synthetases in the activation of amino acids?

Aminoacyl synthetases catalyze the activation of amino acids by reacting them with ATP to form aminoacyl adenylate.

What components are required to form the translation initiation complex?

<p>The initiation complex requires initiation factors, mRNA, initiator tRNA, and the small and large ribosomal subunits.</p> Signup and view all the answers

What is the function of the P-site and A-site in the ribosome during translation?

<p>The P-site binds to the growing peptide, while the A-site binds the aminoacyl tRNA.</p> Signup and view all the answers

How does the initiator tRNA recognize the start codon in the mRNA?

<p>The initiator tRNA recognizes the start codon AUG through complementary base pairing with the mRNA.</p> Signup and view all the answers

What occurs during the activation of amino acids before translation?

<p>Amino acids are activated by combining with ATP to form aminoacyl adenylate, then reacting with tRNA.</p> Signup and view all the answers

What role do initiation factors play in the translation process?

<p>Initiation factors mediate the formation of the translation complex by helping to bring together mRNA, ribosomal subunits, and initiator tRNA.</p> Signup and view all the answers

What role does the methionyl-charged tRNA (met-tRNA) play in the formation of the 70S ribosome?

<p>The met-tRNA binds to the start codon, allowing the initiation of translation and facilitating the assembly of the complete 70S ribosome.</p> Signup and view all the answers

Describe the steps involved in the elongation phase of translation.

<p>Elongation involves the binding of aminoacyl-tRNA to the A-site, peptide bond formation by peptidyl transferase, and translocation of the ribosome to shift tRNA from A-site to P-site.</p> Signup and view all the answers

What occurs during the termination phase of translation?

<p>Termination occurs when a stop codon is reached, causing a release factor to bind the A-site, leading to the hydrolysis of the peptide from the tRNA and ribosomal subunit dissociation.</p> Signup and view all the answers

Explain the significance of repressor function in regulating protein synthesis.

<p>Repressors inhibit mRNA production by binding to the operator site of DNA, maintaining DNA in a repressed state until an inducer signals the need for protein synthesis.</p> Signup and view all the answers

What are the roles of termination codons UAA, UAG, and UGA in translation?

<p>Termination codons signal the end of protein synthesis; they do not have corresponding tRNA molecules and trigger the release of the newly synthesized polypeptide.</p> Signup and view all the answers

What happens to the protein after being released from the ribosome?

<p>The released protein may undergo post-translational modifications, such as cleavage, association with other proteins, or bonding to sugars or lipids, before becoming fully functional.</p> Signup and view all the answers

Identify the enzyme responsible for peptide bond formation during translation and describe its importance.

<p>The enzyme responsible is peptidyl transferase, which is crucial for catalyzing the formation of peptide bonds between amino acids during protein synthesis.</p> Signup and view all the answers

What is the purpose of translocation in the elongation phase of translation?

<p>Translocation shifts the ribosome along the mRNA, moving the peptidyl-tRNA from the A-site to the P-site and making the next codon available for the next aminoacyl-tRNA.</p> Signup and view all the answers

What is the structure of a nucleoside?

<p>A nucleoside consists of a base linked to a sugar.</p> Signup and view all the answers

List the names of nucleosides derived from ribose.

<p>Cytidine, Thymidine, Uridine, Guanosine, and Adenosine.</p> Signup and view all the answers

What is the difference between a nucleoside and a nucleotide?

<p>A nucleotide includes a nucleoside plus a phosphate group.</p> Signup and view all the answers

What is formed when nucleosides bond with phosphoric acid?

<p>They form nucleotides, specifically phosphoesters of nucleosides.</p> Signup and view all the answers

Name the nucleotide corresponding to adenosine.

<p>Adenylic acid or adenosine monophosphate (AMP).</p> Signup and view all the answers

What bonds connect the nucleotides in a polynucleotide chain?

<p>The nucleotides are connected by 3’,5’-phosphodiester bonds.</p> Signup and view all the answers

How are the carbon atoms of the sugar in nucleosides indicated?

<p>They are indicated using a superscript prime notation (e.g., C1’, C2’, C3’).</p> Signup and view all the answers

What do the terms 'nucleotide' and 'nucleoside phosphate' refer to?

<p>Both terms refer to a nucleotide, which is a nucleoside bonded to one or more phosphate groups.</p> Signup and view all the answers

What role does the inducer play in the function of a repressor?

<p>The inducer binds to the repressor, changing its shape so it can no longer bind to the DNA, allowing mRNA synthesis.</p> Signup and view all the answers

Which antibiotic prevents the proper attachment of tRNA and can cause mRNA misreading?

<p>Streptomycin prevents the proper attachment of tRNA's and causes mRNA misreading.</p> Signup and view all the answers

What are microlesions and how do they differ from macrolesions in DNA mutations?

<p>Microlesions are small deletions within the DNA sequence, while macrolesions involve larger deletions or structural changes in the DNA.</p> Signup and view all the answers

Explain how tetracycline functions as an antibiotic.

<p>Tetracycline prevents the binding of tRNA by binding to the 30S subunit of the ribosome.</p> Signup and view all the answers

What is the significance of silent mutations in DNA?

<p>Silent mutations do not cause any change in the protein, meaning they may not affect the organism's phenotype.</p> Signup and view all the answers

How do mutagens relate to cancer?

<p>Many mutagens are also carcinogens, meaning they can cause changes in the DNA sequence that may lead to cancer.</p> Signup and view all the answers

What effect does chloramphenicol have on protein synthesis?

<p>Chloramphenicol inhibits peptide bond formation, preventing tRNA's from binding during protein synthesis.</p> Signup and view all the answers

What is the outcome when the repressor rebinds to the DNA after sufficient protein synthesis?

<p>When the repressor rebinds to the DNA, it stops further protein synthesis.</p> Signup and view all the answers

What are intercalating agents and how do they affect DNA?

<p>Intercalating agents, like PAH, insert themselves between DNA strands, inhibiting replication and transcription, and can cause deletions.</p> Signup and view all the answers

What is the role of electrophilic compounds in the context of DNA mutations?

<p>Electrophilic compounds interact with DNA bases, which are nucleophiles, leading to potential mutations and carcinogenic effects.</p> Signup and view all the answers

What are alkylating agents and their impact on DNA?

<p>Alkylating agents, such as nitrosamines, attach alkyl groups to DNA bases, leading to mispairing and mutations.</p> Signup and view all the answers

How does the alkylation of guanine affect DNA integrity?

<p>Alkylation at the O6 position of guanine can result in base mispairs, while N7-alkylation can lead to apurinic sites.</p> Signup and view all the answers

Describe the mutagenic effect of nitrosoamines on DNA.

<p>Nitrosoamines can deaminate bases and act as alkylating agents, causing direct mutations in DNA and affecting its structure.</p> Signup and view all the answers

What alterations can hydroxylamine induce in cytosine?

<p>Hydroxylamine modifies cytosine to pair with adenine instead of guanine, resulting in a C-G to T-A transition.</p> Signup and view all the answers

What are common sources of carcinogenic compounds mentioned?

<p>Sources include burnt foods, moldy peanuts, and pollutants like pesticides and industrial chemicals.</p> Signup and view all the answers

Explain how UV light contributes to mutations in DNA.

<p>UV light can cause direct DNA damage, leading to mutations through the formation of pyrimidine dimers.</p> Signup and view all the answers

What are plasmids and how do they replicate?

<p>Plasmids are small, circular, double-stranded DNA molecules that replicate independently of the chromosomal DNA.</p> Signup and view all the answers

What role do restriction enzymes play in recombinant DNA technology?

<p>Restriction enzymes cleave DNA at specific sequences, allowing for the removal of genes and the formation of recombinant DNA.</p> Signup and view all the answers

How do the sticky ends produced by restriction enzymes facilitate the creation of recombinant DNA?

<p>Sticky ends created by restriction enzymes are complementary and can easily reassociate with other DNA fragments.</p> Signup and view all the answers

What is the function of DNA ligase in the process of recombinant DNA formation?

<p>DNA ligase splices together the opened plasmid and the desired gene, sealing the sugar-phosphate backbone.</p> Signup and view all the answers

What occurs when recombinant plasmids are introduced into E.coli cultures?

<p>Recombinant plasmids are taken up by the E.coli bacteria, allowing them to express the new genes.</p> Signup and view all the answers

Describe the process of isolating plasmids from E.coli cells.

<p>E.coli cells are treated with a solution that dissolves cell membranes, releasing their contents, including plasmids.</p> Signup and view all the answers

What happens to the gene from another organism when it's cut out using restriction enzymes?

<p>The restriction enzyme cuts the gene, allowing it to be combined with the opened plasmid's sticky ends.</p> Signup and view all the answers

Why are recombinant DNA molecules important in biotechnology?

<p>Recombinant DNA molecules allow for the manipulation and expression of specific genes, facilitating genetic research and development.</p> Signup and view all the answers

Flashcards

Nucleoside

A nucleoside is a molecule formed by a nitrogenous base linked to a pentose sugar.

Nucleotide

A nucleotide is a nucleoside with one or more phosphate groups attached.

5'-nucleoside monophosphate

A nucleotide where a single phosphate group is attached to the 5' carbon of the sugar.

5'-nucleoside diphosphate

A nucleotide with two phosphate groups attached to the 5' carbon of the sugar.

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5'-nucleoside triphosphate

A nucleotide with three phosphate groups attached to the 5' carbon of the sugar.

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Phosphodiester bond

The bond that links nucleotides together in a polynucleotide chain, connecting the 3' carbon of one nucleotide to the 5' carbon of the next.

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Polynucleotide

A long chain of nucleotides linked by phosphodiester bonds.

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Nucleic acids

Large biomolecules composed of polynucleotide chains, such as DNA and RNA.

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Amino Acid Activation

The process of preparing amino acids for inclusion in a protein chain. It involves linking the amino acid to a tRNA molecule.

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Aminoacyl-tRNA

An activated amino acid attached to a specific transfer RNA (tRNA) molecule.

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Translation

Decoding mRNA into a sequence of amino acids to form a protein.

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Initiation Factors

Proteins that help bring together the necessary components for protein synthesis: mRNA, ribosomes, and initiator tRNA.

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Ribosome P-site

The ribosome site that binds to the growing peptide chain during protein synthesis.

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Ribosome A-site

The ribosome site where the next aminoacyl-tRNA binds during protein synthesis.

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Initiation Codon

The mRNA codon (AUG) that signals the start of protein synthesis.

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Initiation Complex

The assembly of mRNA, ribosomes, and initiator tRNA that's formed at the beginning of protein synthesis.

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Intercalating Agents

Molecules that insert themselves between DNA strands, disrupting replication and transcription.

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Electrophilic Compounds

Molecules attracted to electron-rich areas, like DNA bases.

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Alkylating Agents

Chemicals that add alkyl groups to DNA, causing mutations.

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N7-Alkylation

Alkylation at the N7 position of guanine, leading to apurinic sites.

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O6-Alkylation

Alkylation at the O6 position of guanine causing incorrect base pairing.

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Nitrous Acid (HNO2)

A mutagen that converts cytosine to uracil and adenine to hypoxanthine.

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Hydroxylamine (NH2OH)

A mutagen that converts cytosine to a derivative that pairs with adenine instead of guanine.

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Mutations

Changes in the DNA sequence that can alter protein structure and function.

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Inducer in Gene Regulation

A molecule that binds to a repressor protein, causing a change in the repressor's shape so it can no longer bind to DNA, allowing gene expression.

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Repressor in Gene Regulation

A protein that binds to a specific DNA sequence, blocking the transcription of a gene.

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How do antibiotics inhibit protein synthesis?

Antibiotics target bacterial ribosomes, interfering with protein synthesis. They can prevent tRNA binding, peptide bond formation, or ribosome translocation.

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Chloramphenicol's effect

Chloramphenicol binds to bacterial ribosomes, inhibiting peptide bond formation and preventing tRNA binding, halting protein synthesis.

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Erythromycin's effect

Erythromycin blocks the translocation of the ribosome along mRNA, preventing the elongation of the polypeptide chain.

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Puromycin's effect

Puromycin causes premature termination of protein synthesis, leading to the release of an incomplete protein.

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Streptomycin's effect

Streptomycin binds to the bacterial ribosome, causing errors in tRNA binding and mRNA decoding, resulting in faulty proteins.

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Tetracycline's effect

Tetracycline inhibits the binding of tRNA molecules to the ribosome, preventing the addition of amino acids to the polypeptide chain.

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Translation Initiation

The first stage of protein synthesis, where the ribosome assembles on the mRNA and the first amino acid (methionine) is added.

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70S Ribosome

The complete, functional ribosome in prokaryotes, formed by the association of the small (30S) and large (50S) ribosomal subunits.

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Elongation (Translation)

The second stage of protein synthesis, where amino acids are added one by one to the growing polypeptide chain.

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A-site (Aminoacyl-tRNA Binding Site)

The site on the ribosome where the next aminoacyl-tRNA carrying the next amino acid to be added binds.

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Peptidyl Transferase

An enzyme within the ribosome that catalyzes the formation of peptide bonds between amino acids during translation.

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P-site (Peptidyl-tRNA Binding Site)

The site on the ribosome where the tRNA carrying the growing peptide chain is located.

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Termination (Translation)

The final stage of protein synthesis, where the ribosome encounters a stop codon, releasing the completed protein.

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Plasmid

A small, circular, double-stranded DNA molecule found in bacteria that replicates independently of the chromosome.

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Recombinant DNA

A DNA molecule that contains genetic material from different sources. It is formed by combining a gene of interest with a plasmid.

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Restriction enzyme

An enzyme that cuts DNA at specific nucleotide sequences.

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Sticky Ends

Short single-stranded DNA sequences created by a restriction enzyme that can hydrogen bond to complementary sequences.

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DNA Ligase

An enzyme that joins DNA fragments by forming phosphodiester bonds.

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What purpose do restriction enzymes serve in genetic engineering?

Restriction enzymes are used to cut DNA at specific sites, creating fragments with sticky ends that can be combined with other DNA fragments to create recombinant DNA.

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How are sticky ends used in genetic engineering?

Sticky ends, created by restriction enzymes, allow for the specific and efficient joining of DNA fragments that have complementary sequences, forming recombinant DNA.

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What is the role of DNA ligase in genetic engineering?

DNA ligase joins DNA fragments together by forming phosphodiester bonds, creating a complete, stable recombinant DNA molecule.

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Study Notes

Nucleic Acids

  • Nucleic acids were discovered in 1869 by Friedrich Miescher while studying cell nuclei.
  • They are acidic and are found throughout the cell, not just in the nucleus.
  • Nucleic acids (primarily DNA) are the fundamental molecules responsible for replicating genetic information.
  • The genome (total DNA) stores the instructions for cell activities, development, growth, reproduction, and death.
  • The genetic code is encoded in the nucleic acid's primary structure and directs metabolic activities.
  • This genetic message is transcribed by mRNA and translated into proteins by tRNA and rRNA.

Composition of Nucleic Acids

  • Nucleic acids are composed of nucleotides.
  • Nucleotides consist of a nitrogenous base, a sugar (ribose or deoxyribose), and a phosphate group.
  • Bases are heterocyclic amines with common and rare tautomers.
  • Purines: Adenine and Guanine (bicyclic)
  • Pyrimidines: Cytosine, Thymine, and Uracil (monocyclic)
  • Sugars: β-D-ribose (RNA) and β-D-2'-deoxyribose (DNA)
  • Phosphate: Phosphoric acid

Nucleosides and Nucleotides

  • Nucleosides are formed by combining a nitrogenous base with a sugar (ribose or deoxyribose).
  • Nucleotides are formed by adding a phosphate group to a nucleoside.
  • Nucleotides are the building blocks of nucleic acids.
  • Examples of nucleosides: Cytidine, Thymidine, Uridine, Guanosine, and Adenosine; and their deoxyforms.

Polynucleotides

  • Nucleotides are linked together by 3',5'-phosphodiester bonds.
  • This creates a polynucleotide chain (the chain that forms the DNA or RNA structure).
  • Phosphodiester bonds are strong and form the backbone of nucleic acids.

Names of Nucleotides

  • Adenylic acid/adenosine monophosphate (AMP)
  • Guanylic acid/guanosine monophosphate (GMP)
  • Cytidylic acid/cytidine monophosphate (CMP)
  • Uridylic acid/uridine monophosphate (UMP)
  • Thymidylic acid/thymidine monophosphate (TMP)
  • 5'-nucleoside diphosphates (ADP, GDP, CDP, UDP, TDP)
  • 5'-nucleoside triphosphates (ATP, GTP, CTP, UTP, TTP)

Polynucleotides and Nucleic Acids

  • Polynucleotide chains are formed by linking nucleotides through 3',5'-phosphodiester bonds.
  • This forms the sugar-phosphate backbone of DNA or RNA.
  • The bases of the nucleotides extend into the center, perpendicular to the backbone.

DNA Structure

  • DNA is a double helix.
  • The two antiparallel strands run in opposite directions (5' to 3' and 3' to 5').
  • Complementary base pairing occurs (A with T, G with C), via hydrogen bonds.
  • DNA strands are held together by these hydrogen bonds.

DNA Replication

  • DNA replication is semiconservative.
  • Two identical DNA molecules are created from one starting molecule.
  • The process involves unwinding the double helix and each strand serving as a template for a new strand.
  • Leading strand synthesis is continuous, lagging strand synthesis is discontinuous.

Transcription

  • Transcribes DNA information to messenger RNA (mRNA).
  • Complementary base pairing occurs; U replaces T in RNA.
  • RNA polymerase uses DNA as a template, creating a complementary RNA molecule.
  • The process can be summarized as DNA template -> mRNA.

Types of RNA

  • mRNA, tRNA, and rRNA
  • mRNA carries the genetic code from DNA to the ribosome.
  • tRNA brings amino acids to the ribosomes during protein synthesis.
  • rRNA forms the ribosome, the site of protein synthesis.

Post-transcriptional Modification

  • mRNA undergoes processing steps: 5' cap addition, 3' polyadenylation, and intron removal.
  • Introns are non-coding regions. Exons are the coding parts
  • mRNA splicing joins the exons after intron removal.

Protein Synthesis (Translation)

  • The mRNA sequence directs the assembly of amino acids to form a protein.
  • Ribosomes read the mRNA sequence.
  • tRNA carries specific amino acids to the ribosome.
  • Amino acids are joined together to form a polypeptide chain.

Mutations

  • Mutations are alterations in the DNA sequence.
  • They can be caused by spontaneous events (like tautomeric shifts) or induced factors (like chemical mutagens or radiation).
  • Types of mutations include point mutations (substitutions) and frameshift mutations (insertions/deletions).

Gene Regulation

  • The expression of a gene may be regulated by different mechanisms in response to a variety of factors.
  • Transcription factors regulate the initiation of transcription
  • DNA methylation, chromatin structure, and other techniques control gene activity/expression
  • Regulatory genes have sequences called promoters, enhancers or silencers

Cancer

  • Cancer is caused by uncontrolled cell growth and division.
  • Mutations in genes that control cell cycle and growth can lead to cancer.
  • Various factors like chemical mutagens, radiation, and viral infections can cause DNA damage leading to mutations

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Description

This quiz explores the discovery, composition, and functions of nucleic acids, primarily focusing on DNA and RNA. Learn about the molecular structure, nucleotides, and the roles they play in genetic coding and protein synthesis. Test your understanding of key concepts related to the genetic information within cells.

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