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DNA160-page8 - for DNA replication The process of DNA...

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DNA: Structure and Replication - 8 DNA Replication DNA is a double stranded molecule. The two chains (or strands) are attached by hydrogen bonds between the nitrogen bases. The two strands are anti-parallel to each other (run in opposite directions). That is, the 3' carbon of the sugar (the free sugar end) starts one strand and the 5' carbon sugar end (the free phosphate end) starts the other. This is necessary for the base pairs to hydrogen bond correctly. Adenine must bond to thymine, and guanine must bond to cytosine. The adenine-thymine and cytosine-guanine bonding requirement is known as complementary base pairing. Because of the complementary base pairing, if one side of the double stranded molecule is known, we automatically know what the other half is. This model for DNA replication is known as the semi-conservative model
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Unformatted text preview: for DNA replication. The process of DNA Replication There are three basic steps to DNA replication: • The two DNA strands of the parental chromosome must unwind and separate. • Each strand of the parent chromosome serves as a template for the synthesis of a daughter strand. DNA is always synthesized in the 5' ± 3' direction from the 3' ± 5' parent strand template. It helps to remember that the 5' end is the free phosphate (PO 4- 3 ) end, and the 3' end is the –OH end of the sugar. • The newly synthesized double helix of each parent-daughter combination rewinds to form the DNA chains of a replicated chromosome. Each new DNA molecule is composed of one-half of the parent chromosome and one-half newly synthesized DNA....
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