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lec 12 GOB Chemistry: Nucleic Acid Structure and Function

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Terms in this set (20)

  • What are the three main components of a nucleotide?

    Heterocyclic nitrogenous base, sugar (ribose or deoxyribose), and phosphate group.

  • Difference between a nucleoside and a nucleotide?

    A nucleoside consists of a sugar and a nitrogenous base, while a nucleotide also includes one or more phosphate groups.

  • What are the two types of nitrogenous bases in nucleotides?

    Purines (adenine and guanine) and pyrimidines (cytosine, thymine in DNA, uracil in RNA).

  • Which bases are found only in DNA and RNA respectively?

    Thymine (T) is found only in DNA; Uracil (U) is found only in RNA.

  • What type of sugar is found in DNA and RNA nucleotides?

    DNA contains deoxyribose (lacking an OH at carbon 2), and RNA contains ribose.

  • How are nucleotides linked to form nucleic acids?

    By phosphodiester bonds between the 3' hydroxyl of one sugar and the 5' phosphate of the next, forming a sugar-phosphate backbone.

  • What is the directionality convention for writing nucleic acid sequences?

    Sequences are written from the 5' end to the 3' end.

  • What are the key structural features of double-stranded DNA?

    Double helix with antiparallel strands, phosphate backbone on the outside, bases paired inside, and planar bases perpendicular to backbone.

  • How many hydrogen bonds form between A-T and G-C base pairs?

    A-T pairs form 2 hydrogen bonds, and G-C pairs form 3 hydrogen bonds.

  • What forces stabilize the DNA double helix besides hydrogen bonding?

    Dispersion forces (stacking interactions) between aromatic bases provide most of the structural stability.

  • How do proteins generally interact with DNA?

    Through ionic interactions between positively charged amino acids (Arg, Lys, His) and negatively charged phosphate groups on DNA.

  • What is chromatin?

    Chromatin is the compact, orderly tangle of DNA and proteins (including histones) present in non-dividing cells.

  • What is a nucleosome?

    A nucleosome is DNA wrapped around histone proteins, forming the basic unit of chromatin structure.

  • Why do histones contain many lysine and arginine residues?

    Because these basic amino acids are positively charged and form electrostatic salt bridges with negatively charged DNA phosphates.

  • What are Chargaff's rules?

    In double-stranded DNA, the amount of adenine equals thymine, and the amount of guanine equals cytosine.

  • What is the reverse complement of a DNA sequence?

    The sequence complementary to the original strand, written in the opposite 5' to 3' direction, pairing A-T and G-C.

  • How does DNA complementarity facilitate replication?

    Each strand serves as a template to synthesize a new complementary strand, ensuring accurate copying of genetic information.

  • What is the Central Dogma of molecular biology?

    Information flows from DNA to RNA (transcription) and from RNA to protein (translation).

  • What is semiconservative replication?

    Each new DNA double helix contains one original (parental) strand and one newly synthesized strand.

  • How can mutations arise in DNA?

    Mutations can be caused by mutagens like UV radiation or oxidative damage, altering base pairing and potentially propagating during replication.