Polymerases are enzymes that polymerize polynucleotides to create DNA or RNA molecules. They reduce the energy required to form bonds between nucleotides. DNA polymerases I, II, III, and IV play different roles in DNA synthesis and repair. RNA polymerases I, II, and III transcribe different sections of DNA for ribosome, mRNA, and tRNA production. Proofreading is done during replication to correct errors and mutations.
Polymerase is a type of enzyme found within cells involved in the polymerization of a polynucleotide or the creation of DNA or RNA molecules. Enzymes are complex proteins that take part in chemical reactions within cells, while remaining unchanged after the reaction. Most enzymes reduce the amount of energy required for the reaction to take place, called the activation energy. These types of enzymes are called catalysts.
DNA and RNA are made up of long strands of nucleotides. Specifically, DNA is composed of adenine, guanine, cytosine and thymine. RNA is made up of strands of adenine, guanine, cytosine and uracil instead of thymine. Polymerase enzymes reduce the energy required to form bonds between nucleotides, thus allowing for the production of larger molecules. There are different types of polymerases, but all are involved in reactions involving DNA or RNA.
There are a variety of DNA polymerases, each with a separate role. DNA polymerases I, II, III and IV all play a role in the synthesis of a DNA molecule. DNA Pol III is the major enzyme involved in DNA replication. DNA Pol II is the enzyme involved in DNA repair, while DNA Pol I plays a role in DNA molecule synthesis and error correction after DNA Pol III creates the new molecule.
Polymerases have high accuracy, but errors can occur within the genetic code, which can cause mutations in cells and the organism. Proofreading is done as the DNA molecule is replicated and if an error is found, DNA Pol 1 can do the proofreading. When replication fails, DNA Pol II scans the molecules for any errors or gaps that may have occurred over time. DNA Pol IV, or SOS repair polymerase, is found only within bacterial systems and is one possible theory behind bacterial evolution.
As with DNA polymerase, there are also several RNA polymerases. RNA polymerase I, II and III, or Pol I, II and III, exist in higher level multicellular organisms. Each polymerase is responsible for transcription of a particular section of DNA during transcription.
Pol I transcribes those genes that encode part of the ribosome. Ribosomes are the organelles where transcription takes place within cells and each consists of one large and one small subunit. Genes transcribed by Pol I produce the large subunit and part of the small subunit. Pol II transcribes genes for messenger RNA, mRNA and Pol III transcribes genes for transfer RNA, tRNA. The mRNA is the blueprint for translation, or making new proteins, and the tRNA carries single amino acids to the ribosome and the mRNA for linking into a larger chain to form the protein.
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