Nucleic Acids and Their Components Quiz
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Questions and Answers

What are the two main types of nucleic acids mentioned in the content?

  • Ribonucleic acid (RNA) and deoxyribonucleic acid (DNA) (correct)
  • Amino acids and histones
  • Lipids and carbohydrates
  • Protein and nucleotides

    • What is the primary function of RNA in cells?

  • Translates genetic information into proteins (correct)
  • Stores genetic information
  • Replicates DNA
  • Synthesize nucleotides

    • What sugar is found in RNA?

  • 2-Deoxy-D-Ribose
  • D-Ribose (correct)
  • Glucose
  • Ribulose

    • Which of the following correctly describes a nucleotide?

    <p>A nitrogen base connected to a sugar and phosphate group</p> Signup and view all the answers

    What is the significance of a glycosidic bond in nucleotides?

    <p>It forms connections between bases and sugars</p> Signup and view all the answers

    How is a deoxyribonucleoside different from a nucleoside?

    <p>It contains one less oxygen in the sugar</p> Signup and view all the answers

    What suffix is used for nucleosides derived from pyrimidine bases?

    <p>-ine</p> Signup and view all the answers

    Which abbreviation corresponds to deoxyadenosine 5'-monophosphate?

    <p>dAMP</p> Signup and view all the answers

    What defines a nucleotide?

    <p>Base + Sugar + Phosphate</p> Signup and view all the answers

    Which statement is true about the secondary structure of DNA?

    <p>Guanine pairs with cytosine by three hydrogen bonds.</p> Signup and view all the answers

    What role do histones play in the structure of DNA?

    <p>They assist in condensing DNA into chromatin.</p> Signup and view all the answers

    How is the primary structure of nucleic acids determined?

    <p>By the sequence of nucleotides.</p> Signup and view all the answers

    What is a characteristic difference between DNA and RNA?

    <p>DNA is larger and more complex than RNA.</p> Signup and view all the answers

    What is the reading direction of the DNA base sequence?

    <p>From 5’ to 3’ end.</p> Signup and view all the answers

    What is chromatin composed of?

    <p>Nucleosomes assembled into fibers.</p> Signup and view all the answers

    How many chromosomes do humans have?

    <p>46 chromosomes.</p> Signup and view all the answers

    What type of mutation is characterized by replacing one base in the DNA sequence with another?

    <p>Point mutation</p> Signup and view all the answers

    Which type of mutation can lead to different sequences of amino acids due to a shift in the reading frame?

    <p>Frameshift mutation</p> Signup and view all the answers

    What is a consequence of a somatic cell mutation?

    <p>It is confined to that cell and its daughter cells</p> Signup and view all the answers

    What term describes a mutation that has no significant effect on the resulting protein?

    <p>Silent mutation</p> Signup and view all the answers

    Which of the following is necessary for the formation of recombinant DNA?

    <p>An enzyme that cleaves DNA</p> Signup and view all the answers

    What happens when one or more nucleotides are lost from a DNA molecule?

    <p>Deletion mutation occurs</p> Signup and view all the answers

    Which mutation could potentially lead to genetic diseases that are inheritable?

    <p>Germ cell mutation</p> Signup and view all the answers

    What is formed when bacterial plasmid DNA is cut at specific sites by restriction endonucleases?

    <p>Sticky ends</p> Signup and view all the answers

    What is the primary function of messenger RNA (mRNA)?

    <p>Transmits genetic information from DNA to ribosomes</p> Signup and view all the answers

    Which statement accurately describes the process of DNA replication?

    <p>It is semiconservative and involves unwinding the double helix</p> Signup and view all the answers

    What is the role of ribosomal RNA (rRNA) in the cell?

    <p>Makes up the ribosome structure and aids in protein synthesis</p> Signup and view all the answers

    During DNA replication, what is the function of helicases?

    <p>Unwind the DNA double helix</p> Signup and view all the answers

    What distinguishes the leading strand from the lagging strand during DNA replication?

    <p>The leading strand is synthesized continuously</p> Signup and view all the answers

    What is the purpose of RNA primers in DNA replication?

    <p>They serve as starting points for DNA synthesis</p> Signup and view all the answers

    Which enzyme catalyzes the formation of new DNA strands?

    <p>DNA Polymerase</p> Signup and view all the answers

    What defines the origin of replication?

    <p>The site on the DNA where replication begins</p> Signup and view all the answers

    What is the primary role of DNA ligase in recombinant DNA technology?

    <p>To combine two pieces of DNA</p> Signup and view all the answers

    Which component is essential for the Polymerase Chain Reaction (PCR) process?

    <p>Nucleoside triphosphates</p> Signup and view all the answers

    What happens to the amount of DNA after each cycle of PCR?

    <p>It doubles</p> Signup and view all the answers

    What is the significance of using antisense agents in genetic studies?

    <p>To bind and potentially degrade target RNA</p> Signup and view all the answers

    In which method is DNA amplified before being used for DNA fingerprinting?

    <p>Polymerase Chain Reaction (PCR)</p> Signup and view all the answers

    What technique is used to separate DNA fragments by size after restriction enzyme digestion?

    <p>Gel electrophoresis</p> Signup and view all the answers

    Which of the following is NOT a necessary component for PCR?

    <p>Gel medium</p> Signup and view all the answers

    What is a unique feature of an individual's DNA that allows for its use in identification?

    <p>It is entirely unique to the individual</p> Signup and view all the answers

    What is the primary function of a codon?

    <p>To specify a particular amino acid</p> Signup and view all the answers

    How many stop codons are there in the genetic code?

    <p>3</p> Signup and view all the answers

    Which nucleotide sequence will tRNA recognize when translating the mRNA codon UCA?

    <p>AGU</p> Signup and view all the answers

    During which stage of translation does the ribosome encounter a stop codon?

    <p>Termination</p> Signup and view all the answers

    What role does AUG play in protein synthesis?

    <p>It signals the start and codes for methionine.</p> Signup and view all the answers

    What is a ribosome's function during protein synthesis?

    <p>To facilitate peptide bond formation between amino acids</p> Signup and view all the answers

    How many amino acids can be specified by the 64 possible codons?

    <p>20</p> Signup and view all the answers

    What is the role of the tRNA acceptor stem?

    <p>To provide a free OH group for amino acid binding</p> Signup and view all the answers

    Study Notes

    Introduction

    • Each cell in the human body contains many different proteins.
    • Cells must choose which proteins to create from a large number of possible amino acids.
    • Hereditary information is transmitted in the nucleus, specifically chromosomes.
    • Chromosomes are largely made up of histones and nucleic acids.

    Nucleic Acids

    • Nucleic acids are the backbones of chromosomes
    • They include Ribonucleic acid (RNA) and Deoxyribonucleic acid (DNA).

    Nucleic Acids Details

    • DNA stores an organism's genetic information and transmits it across generations.
    • RNA translates DNA's genetic information into proteins needed for cellular functions.
    • Both RNA and DNA are unbranched polymers consisting of nucleotides.

    Nucleotide Structure

    • A nucleotide is composed of:
      • Nitrogen-containing bases (amines)
      • Sugars (monosaccharides)
      • Phosphate

    Bases

    • DNA and RNA contain four bases:
      • Adenine (A)
      • Guanine (G)
      • Cytosine (C)
      • Thymine (T) (in DNA only)
      • Uracil (U) (in RNA only)

    Sugars

    • RNA contains D-ribose sugar
    • DNA contains 2-deoxy-D-ribose sugar (lacks an oxygen on carbon 2)

    Nucleoside

    • Formed when a nitrogen atom of the base forms a glycosidic bond to a sugar's anomeric carbon.
    • Nucleoside = Base + Sugar
    • Named using suffixes (-idine for pyrimidines, -osine for purines, and prefix deoxy- for deoxyribonucleosides).

    Nucleotide (continued)

    • Nucleotides form when a sugar's 5' hydroxyl group bonds to a phosphate.
    • Example: Cytidine 5'-monophosphate (abbreviated as CMP)
    • Another example: Deoxyadenosine 5'-monophosphate (abbreviated as dAMP)

    Primary Structure of DNA and RNA

    • DNA/RNA are chains of nucleotides.
    • The nucleotide sequence/order dictates the order of amino acids in the protein.
    • Nucleotides are arranged from the 5' end (free phosphate) to the 3' end (free hydroxyl).
    • The sequence is read from 5' end to 3' end.
    • Examples: ACGU

    Secondary Structure of DNA

    • DNA forms a double helix structure.
    • The DNA model was proposed by Watson and Crick in 1953.
    • Hydrogen bonds link paired bases (Adenine-Thymine, Guanine-Cytosine).
    • Hydrophobic bases are located in the inside, hydrophilic sugar-phosphate backbone on the outside.

    Complementary Base Pairs

    • Adenine (A) pairs with Thymine (T) by two hydrogen bonds.
    • Guanine (G) pairs with Cytosine (C) by three hydrogen bonds.

    Higher Structure of DNA

    • DNA is coiled around histones
    • Histones are rich in basic amino acids and attract the acidic DNA.
    • Coils form a chain of nucleosomes.
    • Nucleosomes form a solenoid structure (six nucleosomes per turn)
    • Nucleosomes further condense into chromatin fibers, loops, and minibands for the superstructure.
    • This condensation provides a compact form for the chromosomes.

    Chromosome & Gene

    • DNA molecules have a huge number of nucleotides. RNA molecules have fewer.
    • DNA is located in the chromosomes in the nucleus, with each chromosome having a unique type of DNA.
    • Humans have 46 chromosomes.
    • A gene is part of the DNA responsible for a single protein (1000-2000 nucleotides).

    Difference Between DNA & RNA

    • DNA has four bases (A, G, C, and T); RNA has four bases (A, G, C, and U).
    • DNA's sugar is 2-deoxy-D-ribose; RNA's sugar is D-ribose.
    • DNA is usually double-stranded; RNA is single-stranded.
    • RNA is typically smaller than DNA.

    RNA Molecules

    • RNA transmits genetic information needed for cell operation.
    • Ribosomal RNA (rRNA) is found in ribosomes, essential for protein synthesis.
    • Messenger RNA (mRNA) carries genetic information from DNA to ribosomes (formed through transcription); important in protein synthesis.
    • Transfer RNA (tRNA) is the smallest RNA, converting mRNA's genetic information into amino acids for protein synthesis.

    Functions of DNA

    • DNA replicates itself during cell division.
    • It provides the information to create RNA, proteins, and enzymes.

    Replication

    • DNA separates into two original strands.
    • Two new daughter strands are formed using the original strands as templates.
    • Replication occurs by breaking hydrogen bonds.
    • Replication is bidirectional(occurs in both directions).
    • Replication is semiconservative (each new molecule has one original strand and one newly synthesized strand).
    • Replication occurs in several places along the helix simultaneously.

    Replication (Mechanism)

    • Enzymes involved:
      • Helicase: unwinds DNA double helix.
      • Primase: synthesizes primers needed for strand duplication.
      • DNA polymerase: joins nucleotides to build new strands.
      • Ligase: joins Okazaki fragments on the lagging strand.

    Protein Synthesis

    • Gene expression is the activation of a gene to produce a specific protein.
    • The base sequence of a gene determines a particular protein's creation.
    • Only a small percentage of DNA contains genes.

    Gene Expression

    • Transcription
      • mRNA is synthesized
    • Translation
      • mRNA directs amino acid sequence.

    Transcription

    • DNA's genetic information is copied to make mRNA.
    • Starts when the DNA segment unwinds.
    • DNA polymerase initiates mRNA synthesis.
    • The DNA splits into two strands.
    • Template strand is used to create RNA.
    • Information strand(coding) is not used.
    • Transcription runs from 3' to 5' end of the template.
    • mRNA is released once complete, and DNA reforms.
    • A pairs with U (instead of T).
    • Polymerase moves along DNA forming base bonds

    Transcription (Sample Problem)

    • Given a template strand of DNA, determine the mRNA and informational strand sequences.

    Translation

    • mRNA carrying genetic information leaves the nucleus and enters the ribosomes.
    • tRNA converts the information into amino acids.
    • Amino acids are arranged in the proper order.
    • Protein synthesis occurs.

    Genetic Code

    • Language that relates mRNA nucleotides to their corresponding amino acids.
    • The mRNA nucleotide sequence determines the order of amino acids.
    • Codons
      • Groups of three bases on mRNA.
      • Each codon corresponds to a particular amino acid.
      • All 20 amino acids have codons.
    • UGA, UAA, and UAG are stop signals, signaling the end of protein synthesis
    • AUG signals the start and codes for methionine (Met)

    tRNA (Transfer RNA)

    • tRNA translates codons into specific amino acids.
    • Contains 70-90 nucleotides.
    • The end called the acceptor stem always has the nucleotide ACC and a free OH group binding to a specific amino acid.
    • Anticodon
      • Sequence of three nucleotides on tRNA.
      • Complementary to three bases on mRNA.
      • Helps tRNA identify the needed amino acid

    Translation (Further Details)

    • mRNA attaches to ribosome's small subunit.
    • tRNA molecules bring specific amino acids to the mRNA.
    • Amino acids create peptide bonds.
    • Ribosome moves along mRNA until the end of the codon (translocation).
    • Polypeptide chain is released, becoming an active protein
    • Sometimes several ribosomes (polysomes) translate the same strand of mRNA simultaneously.

    Termination

    • Ribosome encounters stop codon (UAA, UAG, or UGA).
    • No tRNA complements these signal codons.
    • Enzyme releases the completed polypeptide chain (now an active protein).

    Translation Stages

    • Initiation: mRNA binds to ribosome small subunit
    • Elongation: tRNA brings amino acids to the growing chain; peptide bonds form
    • Termination: ribosome encounters a stop codon; polypeptide is released

    Mutation

    • Heritable change to a DNA nucleotide sequence.
    • Changes the amino acid sequence, which affects protein structure and function.
    • Can affect enzyme function or be random events.
    • Example causes: X-rays, overexposure to UV light, chemicals (mutagens), or viruses.

    Effect of Mutations

    • Somatic cells (non-reproductive)
      • Mutations are limited to that cell and its progeny.
    • Germ cells (reproductive)
      • Mutations in germ cells affect the organism and all future generations.

    Types of Mutations

    • Point mutation
      • Replacement of one base.
      • Alters a single amino acid.
    • Frameshift mutation
      • Addition or deletion of one or more bases.
      • Causes a change in the reading frame (codon sequence).
      • Altering most amino acids that follow.

    Point Mutation (Examples)

    • Single amino acid substitutions can cause conditions like sickle cell anemia.

    Silent Mutation

    • The resulting amino acid remains unchanged.
    • Has little or no effect on the organism

    Recombinant DNA

    • Synthetic DNA composed of segments from various sources
    • Key elements:
      • Host DNA molecule
      • Enzyme to cut DNA.
      • Gene from a second source organism

    Recombinant DNA - Process

    • Plasmid DNA from bacteria is cut by a restriction enzyme.
    • Human DNA is also cut with the same enzyme.
    • Sticky ends allow for combination of human and plasmid DNA.
    • DNA ligase joins the pieces of DNA.
    • Forms recombinant DNA.

    Recombinant DNA Technology

    • Introduction of human gene of interest into bacterial cells
    • Recombinant bacteria multiplied and produce the human protein.

    Recombinant Applications & Products

    • Production of human medicines (ex: insulin)
    • Genetically altered organisms (e.g., Bt crops).
    • Antisense RNA (e.g., altering gene expression)

    Polymerase Chain Reaction (PCR)

    • Technique amplifying a portion of a DNA molecule.
    • Key Elements:
      • Target DNA segment
      • Primers (short DNA sequences)
      • DNA polymerase enzyme
      • Nucleotide building blocks (A, T, C, G)
    • Process
      • Heat DNA to unwind into single strands
      • Cool to allow complementary primers to anneal.
      • Elevated temperatures allow DNA polymerase to build the complementary strands. -Repeated to exponentially amplify the DNA segment.

    DNA Fingerprinting

    • DNA molecules from individuals are unique.
    • Used as an identification means.
      • DNA extracted and amplified using PCR.
      • DNA is cut into fragments using restriction enzymes.
      • DNA fragments are separated by size using electrophoresis.
      • visualised on an X-ray film; each band corresponding to a DNA segment.

    PCR Applications

    • Prenatal testing, pathogen detection, genetically modified organism analysis, and liquid biopsies

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    Nucleic Acids and Protein Synthesis PDF

    Description

    Test your knowledge on nucleic acids, including DNA and RNA, their structures, and functions. This quiz covers key concepts such as nucleotides, glycosidic bonds, and nucleosides derived from pyrimidine bases. Perfect for biology students seeking to reinforce their understanding of molecular biology.

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