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DNA Synthesis

Write an equation that describes the synthesis of DNA.

A chemical equation that describes the synthesis of DNA can be:

(DNA)n + dNTPs + DNAPol <--------> (DNA)n+1 + PPi (2)

DNAPol = DNA polymerase
(DNA)n = template DNA
(DNA)n+1 = growing new DNA strand
PPi = two pyrophosphate released

dNTPs is an abbreviation for the four deoxyribonucleoside triphosphates that can be added to the template strand. There are four different kinds of deoxyribonucleoside triphosphate (dNTPs) that contain four different bases. (1) The four different bases are adenine, thymine, guanine, and cytosine. The four different deoxyribonucleoside triphosphates are dTTP, dATP, dGTP, dCTP. (1) The deoxyribonucleoside triphosphate's tails have unstable negative charges. As each deoxyribonucleoside triphosphate join the new DNA strand by reacting with the 3'-hydroxyl end of the growing DNA strand, it loses two phosphate groups (PPi). (1) The hydrolysis of the triphosphate group on the deoxyribonucleoside triphosphate will release energy that drives the synthesis of new nucleotide to form DNA. (1) DNA polymerase is an enzyme that help join new deoxyribonucleoside triphosphate into the 3'- OH end of the growing DNA strand. The substrate for DNA polymerase is really the free 3'-OH end and the dNTPs. (3) The product is the dNMP (deoxyribonucleotide monophosphate) that covalently bound to 3' carbon on DNA , and lengthened the DNA with the release of the two pyrophosphate (PPi). (3)

If you do not understand this equation, then I can summarize the overall process of DNA synthesis or replication.

Step1: DNA synthesis begin when special enzyme called DNA helicase bind to specific sequence of DNA known as the origins of replication and unwind the double strand DNA into two strands. RNA primer is needed to initiate the elongation of the DNA on both unwound strands.
Step 2: DNA polymerase is needed to add new DNA nucleotide ( adenine, thymine, guanine, and cytosine) into the free hydroxyl group of the growing DNA strand. DNA polymerase can only add nucleotide to the free 3' OH end of a growing DNA strand. Therefore, new DNA strand can only grow in the 5'-->3' directions. (2) The energy that drive DNA synthesis to form new DNA come from the hydrolysis of the nucleoside triphosphate (dNTPs). The two DNA strand are antiparallel because one strand have the 5'---> 3' orientation, whereas the other strand have the 3'-----> 5' orientation.
Step 3: After DNA polymerase reaches the end of the template strand, it stop replication. Proofreading enzymes are used to check if the nucleotides are correctly paired to the template strand. (1) If there is errors in pairing, a nuclease enzyme will remove the mistake nucleotide. (1)

References -
1. Campbell. Biology. Third Edition
2. http://www.molecularstation.com/wiki/DNA_replication
3. http://wiki.cstl.semo.edu/agathman/DNA%20synthesis%20reaction.ashx

Solution Preview

A chemical equation that describes the synthesis of DNA can be:

(DNA)n + dNTPs + DNAPol <--------> (DNA)n+1 + PPi (2)

DNAPol = DNA polymerase
(DNA)n = template DNA
(DNA)n+1 = growing new DNA strand
PPi = two pyrophosphate released

dNTPs is an abbreviation for the four deoxyribonucleoside triphosphates that can be added to the template strand. There are four different kinds of deoxyribonucleoside triphosphate (dNTPs) that contain four different bases. (1) The four different bases are adenine, thymine, guanine, and cytosine. The four different deoxyribonucleoside triphosphates are dTTP, dATP, dGTP, dCTP. (1) The deoxyribonucleoside triphosphate's tails have unstable ...

Solution Summary

dNTPs is an abbreviation for the four deoxyribonucleoside triphosphates that can be added to the template strand. There are four different kinds of deoxyribonucleoside triphosphate (dNTPs) that contain four different bases. (1) The four different bases are adenine, thymine, guanine, and cytosine. The four different deoxyribonucleoside triphosphates are dTTP, dATP, dGTP, dCTP. (1) The deoxyribonucleoside triphosphate's tails have unstable negative charges. As each deoxyribonucleoside triphosphate join the new DNA strand by reacting with the 3'-hydroxyl end of the growing DNA strand, it loses two phosphate groups (PPi). (1) The hydrolysis of the triphosphate group on the deoxyribonucleoside triphosphate will release energy that drives the synthesis of new nucleotide to form DNA. (1) DNA polymerase is an enzyme that help join new deoxyribonucleoside triphosphate into the 3'- OH end of the growing DNA strand. The substrate for DNA polymerase is really the free 3'-OH end and the dNTPs. (3) The product is the dNMP (deoxyribonucleotide monophosphate) that covalently bound to 3' carbon on DNA , and lengthened the DNA with the release of the two pyrophosphate (PPi). (3)

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