From DNA to mRNA: The Journey Explained

DNA transcription begins in the cell nucleus, where DNA is stored in its characteristic double helix form.The DNA double helix consists of two strands, connected by base pairs and held together by hydrogen bonds.The base pairs follow specific rules: Adenine pairs with Thymine, and Guanine pairs with Cytosine.When transcription needs to begin, a protein called helicase approaches the DNA.Helicase breaks the hydrogen bonds between base pairs, unzipping the DNA strands.This creates a transcription bubble, where the DNA strands are separated.One of these separated strands will serve as the template for mRNA synthesis.This template strand contains the genetic code that will be read in the next step of transcription.RNA polymerase attaches to the promoter region of DNA and begins assembling messenger RNA.The enzyme reads the DNA template strand in the three prime to five prime direction.RNA nucleotides are selected based on complementary base pairing. Unlike DNA which uses thymine, RNA uses uracil to pair with adenine.The RNA strand grows in the five prime to three prime direction, creating a perfect complement to the DNA template.As RNA polymerase continues moving along the DNA, it creates a growing chain of RNA nucleotides that perfectly matches the genetic code of the template strand.The RNA polymerase will continue until it reaches a termination sequence.As RNA polymerase reaches the termination sequence, transcription begins to end.The RNA polymerase recognizes specific sequences that signal the end of transcription.The newly formed mRNA then detaches from the DNA template and RNA polymerase.The mRNA undergoes important modifications. First, a 5-prime cap is added to protect the front end.Then, a poly-A tail is added to the 3-prime end, which helps prevent degradation.In eukaryotic cells, the pre-messenger RNA contains both exons, which code for proteins, and introns, which must be removed.Through a process called splicing, introns are removed and exons are joined together.Finally, the mature messenger RNA, now properly processed and protected, exits the nucleus through nuclear pores.