Nucleic Acids and Nitrogenous Bases
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Questions and Answers

What base in RNA pairs with adenine?

  • Uracil (correct)
  • Guanine
  • Thymine
  • Cytosine

    • Which of the following statements accurately describes RNA compared to DNA?

  • RNA contains equal amounts of specific bases, just like DNA.
  • RNA contains thymine instead of uracil.
  • RNA is double-stranded, while DNA is single-stranded.
  • RNA molecules are generally smaller than DNA molecules. (correct)

    • What is the main function of mRNA?

  • To convert RNA into DNA
  • To protect DNA from damage
  • To stabilize the structure of DNA
  • To facilitate protein synthesis (correct)

    • What type of RNA is formed directly from DNA transcription?

    <p>Heterogeneous nuclear RNA (hnRNA)</p> Signup and view all the answers

    Which of these types of RNA plays a role in processing heterogeneous nuclear RNA to messenger RNA?

    <p>Small nuclear RNA (snRNA)</p> Signup and view all the answers

    What structural feature differentiates RNA from DNA?

    <p>RNA contains uracil, while DNA contains thymine.</p> Signup and view all the answers

    How many nucleotides can a typical RNA molecule range from?

    <p>75 nucleotides to a few thousand nucleotides</p> Signup and view all the answers

    What is a genome?

    <p>All of the genetic material contained in an organism's chromosomes</p> Signup and view all the answers

    What role does RNA polymerase play during transcription?

    <p>It links ribonucleotides to form hnRNA.</p> Signup and view all the answers

    What initiates the end of the transcription process?

    <p>Reaching a sequence of bases that act as a stop signal.</p> Signup and view all the answers

    What are exons in the context of hnRNA?

    <p>Important coding sequences in mRNA.</p> Signup and view all the answers

    Which statement best describes introns?

    <p>They are removed during post-transcription processing.</p> Signup and view all the answers

    What is the primary difference between hnRNA and mRNA?

    <p>hnRNA undergoes editing to become mRNA.</p> Signup and view all the answers

    How does a transcriptome differ from a genome?

    <p>It represents all mRNA molecules produced by a genome.</p> Signup and view all the answers

    What is the main function of mRNA in the cell?

    <p>To carry instructions for protein synthesis.</p> Signup and view all the answers

    What happens to the DNA after transcription is completed?

    <p>It rewinds to reform the double helix.</p> Signup and view all the answers

    What is the primary role of ribosomal RNA (rRNA)?

    <p>To form the structural component of ribosomes</p> Signup and view all the answers

    During the transcription process, which enzyme is responsible for unwinding the DNA double helix?

    <p>RNA polymerase</p> Signup and view all the answers

    In the base pairing process during transcription, which base pairs with adenine in RNA?

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

    Which type of RNA is the largest and plays a role in carrying genetic information to the ribosomes?

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

    What is the main difference between ribose and deoxyribose in RNA and DNA?

    <p>Ribose has an extra hydroxyl group compared to deoxyribose</p> Signup and view all the answers

    How many base pairs of the DNA template strand are exposed at a time during transcription?

    <p>10 base pairs</p> Signup and view all the answers

    What distinguishes transfer RNA (tRNA) from ribosomal RNA (rRNA)?

    <p>tRNA carries amino acids, while rRNA forms ribosomes</p> Signup and view all the answers

    What happens to messenger RNA (mRNA) after it is formed in the nucleus?

    <p>It travels to the cytoplasm for translation</p> Signup and view all the answers

    Study Notes

    Nucleic Acids

    • Nucleic acids are unbranched polymers of nucleotides.
    • Nucleotides consist of a pentose sugar (ribose or 2-deoxyribose), a phosphate group, and a nitrogenous base.
    • Two main types of nucleic acids are DNA and RNA.
      • DNA stores and transfers genetic information.
      • RNA is primarily involved in protein synthesis.

    Nitrogenous Bases

    • Five nitrogen-containing heterocyclic bases exist.

      • Three are pyrimidines (monocyclic): thymine (T), cytosine (C), and uracil (U).
        • Thymine: 5-methyl-2,4-dioxo derivative of pyrimidine.
        • Cytosine: 4-amino-2-oxo derivative of pyrimidine.
        • Uracil: 2,4-dioxo derivative of pyrimidine.
      • Two are purines (bicyclic): adenine (A) and guanine (G).
        • Adenine: 6-amino derivative of purine.
        • Guanine: 2-amino-6-oxo derivative of purine.

    • Pyrimidines are monocyclic, six-membered rings.

    • Purines are bicyclic, consisting of fused five- and six-membered rings.

    Nucleotide Structure

    • Phosphate group is attached to the pentose sugar.
    • Pentose sugar can be ribose or 2-deoxyribose.
    • The nitrogenous base is attached to the pentose sugar (N1 for pyrimidines and N9 for purines).

    Nucleic Acid Structure

    • The alternating sugar-phosphate chain forms the nucleic acid backbone.
      • In DNA, the backbone consists of alternating phosphate and deoxyribose.
      • In RNA, the backbone consists of alternating phosphate and ribose.
      • Each nonterminal phosphate carries a -1 charge.

    Primary Structure

    • The sequence of nucleotides in a nucleic acid.
    • For DNA, the sequence of bases determines the information contained.
    • 5' end normally has a free phosphate group; 3' end has a free hydroxyl group.

    Base Pairing

    • Complementary base pairing is essential for DNA structure and replication.
    • A pairs with T; G pairs with C; in the DNA double helix.
    • Purines pair with pyrimidines to maintain the consistent width of the helix.

    Replication

    • DNA replication is the process of creating exact duplicates of DNA molecules.
    • The DNA double helix unwinds; hydrogen bonds between bases break.
    • Each strand acts as a template for a new complementary strand.
    • DNA polymerase verifies correct base pairing and catalyzes new phosphodiester linkages in the 5'→3' direction.
    • Leading strand grows continuously; lagging strand grows in fragments (Okazaki fragments). DNA ligase connects these fragments.

    Other Key Concepts

    • Chromosomes consist of DNA and proteins (histones).
    • Four major types of RNA: messenger RNA (mRNA), ribosomal RNA (rRNA), transfer RNA (tRNA), and heterogeneous nuclear RNA (hnRNA).
    • Transcription is the process of synthesizing RNA from a DNA template.
      • Involves RNA polymerase.
      • RNA nucleotides are added to the growing RNA strand, complementary to the template DNA strand.
    • Translation is the process of protein synthesis directed by mRNA.
      • Ribosomes read mRNA codons.
      • tRNA molecules bring amino acids corresponding to the codons.
      • Polypeptide chain forms.
    • Splicing involves removing introns and joining exons from hnRNA to produce mature mRNA.

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    Nucleic Acids PDF

    Description

    Explore the fundamental concepts of nucleic acids, including their structure and function. Understand the differences between DNA and RNA and learn about the five key nitrogenous bases. This quiz will test your knowledge of these essential biological components.

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