Where does DNA replication take place and how does DNA replication occur?
Dear Auntie Lisa, Congratulations on your pregnancy! My mom just called and told me, I’m so happy for you and Erv! Now, I know you’re nervous about this pregnancy (being as how your past 30 years old, but a young 32 nonetheless!), and you asked my mom questions about how the baby actually becomes a baby, ie how it inherits genes from your and Erv’s DNA, where the actual “passing on” of genes occurs, but have no fear! Myself and my biology 151 class are here! I’m writing this letter so you know a little bit more about what’s going on inside your tummy while little Hannah (what I think her name should be…elegant, no?) is waiting to be born. First of all, as most people know, DNA is the building blocks of life. DNA, or deoxyribonucleic acid, is a genetic sequence made up of four nucleotides with the bases adenine, thymine, guanine and cytosine, all connected with strong hydrogen bonds (A matches with T, G with C). To clarify, a nucleotide is a deoxyribose sugar attached to one or more phosphate groups, and a base. Here’s a picture to possibly make it a little clearer. These two strands that are separated for replication also have a specific direction in which they “flow”. There is a 3’ and a 5’ end, with the two strands being “anti-parallel”, meaning one is 5’ to 3’, the other flowing 3’ to 5’. DNA replication, like what will happen with your baby and its cells, occurs in the nucleus of a cell, and begins with initiator proteins such as DNA Helicase separating the two strands, creating a replication fork. The DNA unwinds at certain locations in the genome, called origins, and begins replication via a fragment of RNA, a primase, and a member of a family of enzymes specifically used for replicating DNA. These enzymes, such as RNA and DNA Helicase, unwind DNA, add nucleotides that match the template strand, add proteins, and also help with the rest of DNA synthesis. Single-Strand Binding Proteins bind to the DNA and prevent the double helix from re-joining and re-winding. Topoisomerase and DNA Gyrase are two enzymes that also aid in the relaxing of the coil and the relieving of the strain from unwinding the stable and strong structure that is DNA. Next, the DNA polymerase creates a new stand of DNA by extending the 3’ end, adding nucleotides that match the existing sequence. When this occurs, two of