BIO 1130 Study Guide - Thymine, Cytosine, Guanine
DNA structure
-Contains 4 nucleotides made up of:
1. A five-carbon sugar “deoxyribose”
2. Phosphate group (attached to 5’ end of sugar)
3. A nitrogenous base, either: guanine, cytosine, thymine, adenine. The base is
attached to the 1’ end of the sugar.
~Adenine and guanine are purines (they contain a pair of fused rings of carbon
and nitrogen atoms)
~Cytosine and thymine are pyrimidines (containing a single carbon ring)
-Sugar-phosphate backbone:
-Nucleotides are attached to one another from deoxyribose sugar of one to
phosphate group of the other.
-The phosphate group in a nucleotide serves as the attachment for two
deoxyribose sugars, attaching to the 3’ carbon of one sugar and the 5’ carbon of
the next carbon. ****This is called a phosphodiester bond****
-Polarity of polynucleotide chain
-At the 5’ end of the chain, there is a phosphate group attached to the (5’ end) of
the carbon of the deoxyribose sugar
-At the 3’ end of the chain, there is a hydroxyl group (polar) attached to the (3’
end) of the carbon of the deoxyribose sugar
-X-ray diffraction
-Allows for the deduction of the positions of atoms in a crystal, thus X-ray
diffraction of DNA indicates the structure of DNA (helical)
-Complementary base pairing
-Hydrogen bonding gives stability to pairing of nitrogenous bases (in different
strands of DNA) and aids in holding together two strands of DNA
-Cytosine pairs with guanina while thymine pairs with adenine
***These two strands of DNA are linked together in an anti-parallel fashion (the
bases of the 3’ of one end of one strand are attached to the bases of the 5’ end of
the other DNA strand).
*DNA is hereditary information, and stores + transmits genetic information.
-DNA replication
-Semi-conservative replication (new strand is created using the original parental
strand)
-Enzymes (helicase etc) unwind the strands, exposing the nucleotides and making
the nitrogenous bases available for complimentary base pairing
-DNA polymerase will attach free-floating nucleotides in the cell to these exposed
bases on the parental strand (template strand).
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BIO 1130 Full Course Notes
Verified Note
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