DNA Duplication, RNA Transcription and Translation

DNA and RNA Sec. 12-1 DNA is a long molecule made of a combination of 4 nucleotides. Backbone of the molecule is the deoxyribose/phosphate groups. Chargaff’s rule (made by Erwin C.) is that adenine always pairs with thymine and cytosine always pairs with guanine. Between Rosalind Franklin’s xray images of DNA and Watson and Crick’s modeling, the double helix model of DNA was formed. Nitrogenous base pairing (Chargaff’s rule) is made possible by hydrogen bonding between the complimentary base and allows the 2 sides to stick together. DNA and Chromosomes Sec. 12-2 Prokaryotes have no nucleus. DNA is a single circular molecule that contains the cell’s genetic material. Eukaryotic chromosomes contain DNA and proteins (histones) tightly coiled together to form chromatin. During most of the cell cycle chromatin is loosely floating within the nucleus of the cell. During mitosis the chromatin tightly packs and forms chromosomes, getting ready to be duplicated and spread out to new cells. DNA Replication Each strand of DNA is complementary to the other, meaning that one can be constructed via the other through base pairing. In prokaryotes, duplication starts at one point and proceeds in both directions till complete. In eukaryotes, separation and replication takes place at replication forks until all is complete. Specific enzymes unzip the DNA molecule at the hydrogen bonds. DNA polymerase (enzyme) joins individual nucleotides to produce a new DNA molecule. It also proofreads the results to insure a good copy. RNA and Protein Synthesis Sec. 12-3 The segment of DNA that codes for a particular protein is called a gene. Messenger RNA picks up the information from the unzipped DNA and takes it to the ribosomes. Ribosomal RNA picks up the information and then transfer RNA brings in each specific amino acid as instructed by Ribosomal RNA to make the protein. RNA polymerase Binds to DNA, unzips it and uses one strand to make a template of the DNA information. The enzyme binds to regions on the molecule called promoters that determine where to start and stop. The sequence of 3 nitrogenous bases codes for a particular amino acid. All linked together, these amino acids will create a polypeptide called a protein. Messenger RNA goes from the nucleus to the ribosomes. Transfer RNA with its particular amino acid lines its anticodon up along mRNA and creates a protein. The creation of proteins affects all other functions within the organisms because enzymes are proteins. Mutations Sec. 12-4 Mistakes can be made in the sequencing if nucelotides: Point Mutations Frameshift Mutations (Crohn’s Disease)