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The Central Dogma: DNA, RNA, and Proteins. Written by Dallas Duncan and Dr. Frank B. Flanders June 2010. What is DNA?. DNA is short for Deoxyribonucleic Acid DNA is comprised of genes, which are the basic building blocks of life
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The Central Dogma: DNA, RNA, and Proteins Written by Dallas Duncan and Dr. Frank B. Flanders June 2010
What is DNA? • DNA is short for Deoxyribonucleic Acid • DNA is comprised of genes, which are the basic building blocks of life • DNA is made up of nitrogenous bases – adenine, guanine, cytosine, and thymine – coiled into a double helix structure • Like fingerprints, everyone’s DNA is different, varying only by the order of the bases
What is RNA? • RNA is short for Ribonucleic Acid • Very similar to DNA, except it is single-stranded and has the nitrogenous base uracil instead of thymine • RNA is made from DNA, and has many functions, including helping to manufacture proteins • Examples of RNA include tRNA, rRNA, and mRNA
What are Proteins? • Proteins are nutrients made of amino acids arranged in a specific structure • Proteins act as enzymes to catalyze reactions, help cells retain their shapes, and act in cell signaling and adhesion • Necessary part of the human and animal diet
Transcription: RNA Synthesis • DNA unwinds in the nucleus • RNA polymerase recognizes a specific sequence in the DNA, called a promoter, and binds to it • The promoter identifies the start of a gene, which strand should be copied, and what direction it should be copied. • Complementary bases are assembled between the new strand of mRNA and DNA • At the five prime end of the mRNA strand, a cap is added, and a poly-adenine tail is added to the other end. • Introns, or regions of mRNA which don’t contain a genetic message, are removed • Exons, or the remaining portions of mRNA once introns are removed, are put together to form the mature mRNA transcript • The mature mRNA transcript moves out of the nucleus and into the cytoplasm through pores in the nuclear membrane
Translation: Protein Synthesis • A ribosome attaches to the mRNA at a start codon. • tRNA and amino acid complexes bind to an mRNA codon after forming base pairs with a tRNA anticodon • The ribosome moves from codon to codon along the mRNA strand, adding amino acids one by one, as called for by the genetic code • A release factor binds to the stop codon, ending translation and releasing the completed protein from the ribosome