Detailed description of DNA replication and RNA transcription, AP level.
DNA ReplicationThe purpose of DNA replication is to make sure the daughter cell in cell division has its complete set of DNA, which occurs during the S phase of the cell cycle. To for a cell to function, it must have DNA (exact DNA from parent cell), for DNA determines the sequence of nucleotides in mRNA, which in turn determines the sequence of amino acids in proteins, which in turn determines their function.
The template for DNA replication is essentially itself. DNA is uncoiled by helicase, an enzyme that untwists the double helix at the replication forks, separating the two parental strands and making them available as template strands; helicase breaks down the hydrogen bonds between the two strands. New DNA strands will be made on the parental strands; DNA polymerase III adds on complementary nucleotides along the template.
DNA replication occurs in the nucleus of eukaryotic cells and in the cytoplasm of prokaryotes. The replication of a DNA molecule begins at origins of replication. Replication proceeds in both directions from each origin. When helicase unwinds the DNA helix, it forms a y-shaped replication fork where the new strands of DNA elongate. Single-strand binding protein attach to each strand of the uncoiled DNA to keep them separate. DNA elongates in the 5ÃÂ3ÃÂ direction; the leading strand continuously adds nucleotides to a primer while the lagging strand adds nucleotides in Okazaki fragments.
Stages with specific molecules, enzymes, and energy source(s) involved in eachi. Helicase-an enzyme that untwists the double helix of DNA at the replication forks-unwinds the DNA, producing a replication fork. Single-strand binding proteins bind to and stabilize single-stranded DNA until it can be used as a template and prevent them from recombining. Topoisomerase corrects ÃÂoverwindingÃÂ ahead of replication...