DNA and the Gene

Dna polymerase iii then adds bases to the 3 end of

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Unformatted text preview: a free 3’ hydroxyl group that can combine with an incoming dNTP to form a phosphodiester bond. Once the primer is attached to a single- stranded template, DNA polymerase begins working in the 5’ → 3’ direction. Before synthesis, primase, RNA polymerase, must synthesize a short stretch of RNA that acts as a primer for DNA polymerase. Solves our problem of how the first nucleotide gets added. It can start from scratch, doesn’t have to add on to anything, doesn’t have to be synthesized first. It is done by base pairing. This creates another problem. RNA has different complementary pairing. Instead of A- T, it has the pairing of A- U, which must be rid off, as it cannot stay in the genetic code. Synthesis of the lagging strand starts when primase synthesizes a short stretch of RNA that acts as a pimer. DNA polymerase III then adds bases to the 3’ end of the primer. As it synthesizes, the topoisomerases keeps unwinding the DNA double helix, giving even more area for new DNA to be synthesized. These are called okazaki fragments. When a stretch of DNA is free for synthesis, the whole process is repeated again. The RNA primer, primase, helicase and so on. After the leading and lagging strands are synthesized, the RNA primer n...
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This note was uploaded on 02/13/2014 for the course BIO 103 taught by Professor Heidielmendorf during the Fall '10 term at Georgetown.

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