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Nucleic Acids: DNA and RNA Structure
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Nucleic Acids: DNA and RNA Structure

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Questions and Answers

What happens to all bases after a base addition?

Move one position to the right.

What happens to all bases after a base deletion?

Move one position to the left.

Which type of mutations could frame shift mutations lead to?

  • Point mutations
  • Missense mutations
  • Nonsense mutations
  • Both missense and nonsense mutations (correct)
  • What is the result of adding a C between the C and U in the base sequence GCG-CUA-GAG?

    <p>GCG-CCU-AGA-G</p> Signup and view all the answers

    What are the three components that each nucleotide is composed of?

    <p>Phosphate group, Pentose sugar, Nitrogenous bases</p> Signup and view all the answers

    What is the result of deleting the C in the second codon of the base sequence GCG-CUA-GAG?

    <p>GCG-UAG-AG</p> Signup and view all the answers

    What connects complementary bases in DNA?

    <p>Hydrogen bonds</p> Signup and view all the answers

    DNA replication occurs during the G period of Interphase.

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

    Helicase untwists and unzips the DNA helix by breaking the _______ bonds.

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

    Match the following RNA types with their descriptions:

    <p>mRNA = RNA that is ultimately translated and results in the production of protein tRNA = RNA that carries an amino acid to be used in the building of protein rRNA = A structural RNA that comprises the ribosome</p> Signup and view all the answers

    Study Notes

    Nucleic Acids

    • Nucleic acids are composed of nucleotides.
    • Each nucleotide is composed of:
      • A phosphate group
      • A pentose sugar (deoxyribose in DNA or ribose in RNA)
      • Nitrogenous bases (purines and pyrimidines)
    • Purines are larger and double-ringed (adenine and guanine)
    • Pyrimidines are smaller and single-ringed (cytosine, thymine, and uracil)

    DNA Structure

    • DNA is a double helix, with two strands of nucleotides connected and twisted.
    • Hydrogen bonds connect complementary bases (adenine and thymine, or guanine and cytosine).

    The Search for the Genetic Material

    • Frederick Griffith (1928) demonstrated transformation, changing the genotype and phenotype of a cell by assimilation of genetic material from an outside source.
    • Oswald Avery, Maclyn McCarty, and Colin MacLeod (1944) repeated Griffith's experiment, showing that DNA is the transforming agent.

    The Search for the Structure of DNA

    • Erwin Chargaff (1947) discovered that the amount of adenine in a DNA molecule is equal to the amount of thymine, and the amount of guanine is equal to the amount of cytosine (Chargaff's Rule).
    • Maurice Wilkins and Rosalind Franklin (1952) used X-ray crystallography to determine the shape of DNA, showing that it is a three-dimensional double helix.
    • James Watson and Francis Crick (1953) determined the true structure of DNA, winning the Nobel Prize.

    Biological Properties of DNA

    • DNA carries information from generation to generation.
    • DNA must be copied accurately.
    • DNA sometimes mutates, and mutations are copied accurately.
    • DNA must be translated and its information put into action.

    DNA Replication

    • Occurs during the S period of interphase.
    • Takes place within the nucleus of a eukaryotic cell.
    • Involves the production of new DNA from existing DNA templates.
    • The original parent strands separate, and new complementary daughter strands are synthesized.
    • Helicase untwists and unzips the DNA helix, breaking the hydrogen bonds.
    • DNA polymerase builds new DNA nucleotides using a single strand DNA template.
    • One strand (3' to 5') is replicated continuously, while the other strand is antiparallel (5' to 3') and replicated discontinuously.

    DNA Repair

    • Nuclease enzymes remove damaged DNA.
    • DNA polymerase builds new DNA to repair the mistake.
    • DNA ligase pieces together the repaired region to the existing correct region.

    The Central Dogma

    • The flow of genetic material in a eukaryotic cell: DNA → RNA → Protein.
    • Transcription: the production of RNA from a single strand DNA template.
    • Translation: the production of protein from a messenger RNA strand.

    Transcription

    • Helicase untwists and unzips the DNA helix, breaking the hydrogen bonds.
    • RNA polymerase produces new RNA nucleotides from a single strand DNA template.
    • RNA codons are built from DNA codons.
    • Transcription occurs in the nucleus.

    RNA

    • A single strand of nucleotides.
    • RNA base nucleotides are complementary to DNA base nucleotides.
    • If a DNA single strand base sequence reads…., then RNA polymerase would build the complementary RNA sequence.

    Types of RNA

    • mRNA (messenger RNA): RNA that is ultimately translated and results in the production of protein.
    • tRNA (transfer RNA): RNA that carries an amino acid to be used in the building of protein.
    • rRNA (ribosomal RNA): a structural RNA that comprises the ribosome.

    Translation

    • RNA → Protein.
    • mRNA leaves the nucleus and goes to a ribosome.
    • Each mRNA codon codes for the production of an amino acid.
    • tRNA molecules each carry an amino acid and an anticodon that is complimentary to the mRNA codon.
    • Amino acids are linked by peptide bonds.

    Ribosome Structure

    • Consists of a large and a small subunit.
    • mRNA enters the ribosome between the two subunits to be read.
    • The A site accepts a new tRNA molecule, which delivers a new amino acid.
    • The P site holds a tRNA molecule that has a growing chain of amino acids.
    • The E site is the exit site that releases previously used tRNA molecules.

    Genetic Code

    • A dictionary that indicates which amino acids result from each mRNA codon.
    • It is a triplet code, non-overlapping, universal, and degenerate code.
    • Uses a table to determine the amino acid coded for by each mRNA codon.

    Point Mutations

    • A point mutation is a mutation involving a base substitution.
    • If the altered codon does not change the amino acid, it has no effect.
    • If the altered codon codes for a different amino acid, a different protein results (missense mutation).
    • If the altered codon codes for STOP, no protein results (nonsense mutation).

    Frame Shift Mutations

    • Alter the complete base sequence that follows the mutation.
    • A base addition shifts the reading frame to the right, while a base deletion shifts the reading frame to the left.
    • Can lead to missense or nonsense mutations.
    • More harmful than point mutations.

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    Quiz Team

    Description

    Understand the components of nucleotides, including phosphate groups, pentose sugars, and nitrogenous bases, and how they form DNA and RNA molecules.

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