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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
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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
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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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Dehydration Synthesis to Make Phosphodiester Bond
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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?
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Building the polymer
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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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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?
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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
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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
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Watson and Crick … and others… 1953 | 1962
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Maurice Wilkins… and… 1953 | 1962
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Rosalind Franklin (1920-1958)
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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