File Name: enzymes and accessory proteins involved in dna replication .zip
DNA replication has been well studied in prokaryotes primarily because of the small size of the genome and because of the large variety of mutants that are available. This means that approximately nucleotides are added per second. Thus, the process is quite rapid and occurs without many mistakes. DNA replication employs a large number of structural proteins and enzymes, each of which plays a critical role during the process. One of the key players is the enzyme DNA polymerase , also known as DNA pol, which adds nucleotides one-by-one to the growing DNA chain that is complementary to the template strand. Like ATP, the other NTPs nucleoside triphosphates are high-energy molecules that can serve both as the source of DNA nucleotides and the source of energy to drive the polymerization. How does the replication machinery know where to begin?
The prokaryotic chromosome is a circular molecule with a less extensive coiling structure than eukaryotic chromosomes. The eukaryotic chromosome is linear and highly coiled around proteins. While there are many similarities in the DNA replication process, these structural differences necessitate some differences in the DNA replication process in these two life forms. DNA replication in prokaryotes has been extensively studied, so we will learn the basic process of prokaryotic DNA replication, then focus on the differences between prokaryotes and eukaryotes. How does the replication machinery know where to start? It turns out that there are specific nucleotide sequences called origins of replication where replication begins.
The process of translation results in the creation of the complementary DNA strands and results in the creation of two double-stranded DNA molecules that are exact replicas of the original DNA molecule. The complementary strands are created in the 5'-3' direction. Certain DNA polymerases are also responsible for proofreading the newly synthesized DNA strand and using exonuclease to remove and replace any errors that occurred. DNA polymerases are divided into 7 families according to their sequence homology and 3D structure similarities. The order of the nucleotides on the complementary strand is determined by the base-pairing rules: cytosine with guanine and adenine with thymine. This causes the elongation of the new strand in a 5'-3' direction.
During this process, DNA polymerase "reads" the existing DNA strands to create two new strands that match the existing ones. DNA polymerase adds nucleotides to the three prime 3' -end of a DNA strand, one nucleotide at a time. In this way, genetic information is passed down from generation to generation. Before replication can take place, an enzyme called helicase unwinds the DNA molecule from its tightly woven form, in the process breaking the hydrogen bonds between the nucleotide bases. This opens up or "unzips" the double-stranded DNA to give two single strands of DNA that can be used as templates for replication in the above reaction.
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