DNA+Replication

DNA REPLICATION Cells can reproduce either through mitosis or meiosis. But, before this can occur the celll must make a copy of it's chromosomes. The DNA in the chromosomes is replicated in a process called DNA replication. Without DNA replication cells would only have half of the DNA of their parents. If this were to occur, species couldn't survive and organisms couldn't grow or reproduce successfully. So, to keep species alive, they all must undergo DNA replication. A DNA molecule is composed of two strands. Each strand contains a sequence of nucleotides. On one strand you may have thymine which pairs with adenine and in the same way, guanine pairs with cytosine. So if you know the sequence of one strand, you can predict the sequence of the other. Part of the process of DNA replication actually uses this sequencing to replicate. During replication each strand serves as a pattern. Replication begins when an enzyme breaks down the hydrogen bonds between bases that hold the two strands together. This is sort of like unzipping the DNA. As the DNA continues to unzip, nucleotides that are floating free are attached to their base pair by hydrogen bonding. Then another enzyme bonds these nucleotides together. This continues until the entire molecule has been unzipped and replicated. Each new strand is a complement of the original, or parent, strands. When all the DNA in all the chromosomes of a cell have been replicated there are two copies of the organism genetic information, in the form of DNA. Through this the genetic makeup of an organism can be passed on to new cells during mitosis. And it can be passed on to new generations through meiosis after sexual reproduction.

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