The Central Dogma
A. What is the Central Dogma?Genes are coded DNA instructions that control the production of proteins in a cell. In order to decode these genetic messages, part of the nucleotide sequence is copied from DNA to RNA (ribonucleic acid). These RNA molecules contain coded information for making proteins. During transcription, RNA polymerase binds to DNA and separates the DNA strands. RNA polymerase then uses one strand of DNA as a template form which nucleotides are assembled into a strand of RNA.
The properties of proteins are determined by the order in which different amino acids are joined together. The "language" of mRNA instructions is called the genetic code. The four bases of RNA are A, U, C, and G. The genetic code is read three letters at a time. Since there are four different bases, there are 64 possible three-base codons. |
B. What is DNA?DNA stores and transmits the genetic information from one generation of an organism to the next. It is a long molecule of units called nucleotides. Each nucleotide is made up of three basic components: a 5-carbon sugar called deoxyribose, a phosphate group, and a base that contains nitrogen. The four bases of DNA are adenine, guanine, cytosine, and thymine. A always forms with T and G forms with C. DNA is a double helix in which two strands are wound around each other.
DNA image source |
C. What is a gene?All living beings have genes. Genes are responsible for your skin color, eye color, hair, and all the other traits that each individual has. They are a set of instructions that determine what a person is like. The genetic code, which is the "language" of RNA contains four bases: A, U, C, and G. It is read three letters at a time and each "word" of the code is three bases long. A codon consists of three consecutive nucleotides that specify a single amino. There are 64 possible three-base codons that are possibilities of the genetic code.
Genetic Code image source |
D. Transcription and TranslationTranscription is a process in which RNA molecules are produced by copying part of the nucleotide sequence of DNA into a complementary sequence of RNA. It requires an enzyme known as RNA polymerase. During this process, RNA polymerase binds to DNA and separates the DNA strands. RNA polymerase then uses one strand of DNA as a template from which nucleotides are assembled into a strand of RNA.
The nucleotide bases in an RNA molecule serve as instructions for the order in which amino acids should be joined together to produce a polypeptide. Ribosomes are in charge of "interpreting" the instructions. Translation is the decoding of an RNA message into a polypeptide chain. Translation takes place on ribosomes. During this process, the cell uses information from messenger RNA to produce proteins. image source |
E. What is a Protein?Proteins are molecules that are made up of amino acids which our bodies and the cells in our bodies need to function properly. Our muscles, skin, bones, and many other parts of the body contain big amounts of protein. Every cell in our bodies contain many different proteins that work together to run the cell.
Proteins make us fel pain because send sensations of pain. The receptor proteins in our nerve cells pick up the signal and send it on to the next. Structural proteins stack together to form column-like supports that give the cells their shape. Every gene in DNA has information that tells how to make each protein. Protein image source |
F. An Example of Gene ExpressionAn example of gene expression is a firefly's growth process. There are different species of fireflies and they all have different characteristics. One of the reasons that fireflies glow is to protect themselves from predators. Fireflis get protection from a chemical inside their organism which has a nasty taste. After the predator eats the chemical (called lucibufagens) it begins to associate the firefly's glow with this bad taste. The luciferase enzymes that is produced from the firefly, drives a chemical reaction that generates light.
This process is possible because transcription occurs when the RNA polymerase copies the LUC gene-which specifies the sequence of amino acids that make up the luciferase enzyme- in the form of messenger RNA. After the transcription is completed, the LUC mRNA moves to the cytoplasm where it is recognized by the cell's ribosome. In the process of translation, the LUC mRNA produces a string of amino acids that make up the luciferase enzyme. The firefly is able to generate light because the cells in its tail produce thousands of luciferaze enzymes at once. New enymes bind to a chemical called luciferin which forms oxyluciferin. The light is prodeced by the energy of so many luciferase enzymes. This light attracts mates and scares predators. Firefly image source |