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  • 1

    AP Biology 2006-2007

    Nucleic acids

    AP Biology 2006-2007

    Nucleic Acids Information

    storage

    AP Biology proteins

    DNA

    Nucleic Acids § Function:

    u genetic material § stores information

    w genes w blueprint for building proteins

    n  DNA → RNA → proteins § transfers information

    w blueprint for new cells w blueprint for next generation

    AP Biology

    A A

    A

    A

    T C

    G

    C G

    T G

    C T

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    AP Biology

    The compounds that store information/ genetic code for building proteins are

    A. lipids B. nucleic acids C. amino acids D. carbohydrates

    AP Biology

    Nucleic Acids § Examples:

    u RNA (ribonucleic acid) §  single helix

    u DNA (deoxyribonucleic acid) §  double helix

    § Structure: u monomers = nucleotides

    RNA DNA

    AP Biology

    RNA & DNA § RNA

    u single nucleotide chain § DNA

    u double nucleotide chain § N bases bond in pairs

    across chains u spiraled in a double helix

    §  double helix 1st proposed as structure of DNA in 1953 by James Watson & Francis Crick (just celebrated 60th anniversary in 2013!)

    AP Biology

    Information polymer §  Function

    u series of bases encodes information §  like the letters of a book

    u stored information is passed from parent to offspring §  need to copy accurately

    u stored information = genes §  genetic information

    Passing on information? Why is this important?

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    AP Biology

    Nucleotides §  3 parts

    u nitrogen base (C-N ring) u pentose sugar (5C)

    §  ribose in RNA §  deoxyribose in DNA

    u phosphate (PO4) group

    Are nucleic acids charged molecules?

    Nitrogen base I’m the

    A,T,C,G or U part!

    AP Biology

    In electrophoresis

    AP Biology

    Types of nucleotides §  2 types of nucleotides

    u different nitrogen bases u purines

    §  double ring N base §  adenine (A) §  guanine (G)

    u pyrimidines §  single ring N base §  cytosine (C) §  thymine (T) §  uracil (U)

    Purine = AG Pure silver!

    AP Biology

    Nucleic polymer § Backbone

    u sugar to PO4 bond u phosphodiester bond

    §  new base added to sugar of previous base

    §  polymer grows in one direction u N bases hang off the

    sugar-phosphate backbone

    Dangling bases? Why is this important?

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    AP Biology

    Dehydration Synthesis to Make Phosphodiester Bond

    AP Biology

    Pairing of nucleotides § Nucleotides bond between

    DNA strands u H bonds u purine :: pyrimidine u A :: T

    § 2 H bonds u G :: C

    § 3 H bonds

    Matching bases? Why is this important?

    AP Biology

    Building the polymer

    AP Biology

    DNA molecule § Double helix

    u H bonds between bases join the 2 strands § A :: T § C :: G

    H bonds? Why is this important?

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    AP Biology

    Copying DNA § Replication

    u 2 strands of DNA helix are complementary §  have one, can build other §  have one, can rebuild the

    whole

    Matching halves? Why is this

    a good system?

    AP Biology

    When does a cell copy DNA? § When in the life of a cell does DNA have

    to be copied? u cell reproduction

    § mitosis u gamete production

    § meiosis

    AP Biology

    DNA replication “It has not escaped our notice that the specific pairing we have postulated immediately suggests a possible copying mechanism for the genetic material.” James Watson Francis Crick 1953

    AP Biology

    Watson and Crick … and others… 1953 | 1962

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    AP Biology

    Maurice Wilkins… and… 1953 | 1962

    AP Biology

    Rosalind Franklin (1920-1958)

    AP Biology

    Interesting note… §  Ratio of A-T::G-C

    affects stability of DNA molecule u  2 H bonds vs. 3 H bonds u  biotech procedures

    §  more G-C = need higher T° to separate strands

    u  high T° organisms §  many G-C

    u  parasites §  many A-T (don’t know why)

    AP Biology

    Another interesting note… § ATP

    Adenosine triphosphate

    + +

    u modified nucleotide §  adenine (AMP) + Pi + Pi

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    AP Biology

    Review Questions 1. What are the functions of nucleic acids? stores information, transfers information 2. What are the examples of nucleic acids? DNA and RNA 3. What are the monomers of nucleic acids? nucleotides AP Biology

    Review Questions

    4. What molecules and bonds forms the backbone of nucleic acids?

    sugars and phosphates in strong phosphodiester bonds 5. What are the 3 parts of a nucleotide? nitrogen base, pentose sugar, phosphate group

    AP Biology

    Review Questions 6.  What are the 4 nitrogen bases for DNA

    and what is different for RNA? A, C, G, T and U instead of T for RNA

    7. What are the base pairing rules? A to T (or U) and G to C 8. What type of bonds hold the bases

    together in a double strand? H bonds