BIO103 PDF: Central Dogma of life

Course: BIO103 Biology I Central Dogma of Life Most. Naoshia Tasnin, Ph.D. Assistant Professor Department of Biochemistry & Microbiology North South University, Dhaka, Bangladesh E-mail: [email protected] Office: SAC832A...

Course: BIO103 Biology I Central Dogma of Life Most. Naoshia Tasnin, Ph.D. Assistant Professor Department of Biochemistry & Microbiology North South University, Dhaka, Bangladesh E-mail: [email protected] Office: SAC832A 1  Central Dogma of life Central Dogma of Life: An Inheritance Mechanism. In molecular biology, central dogma illustrates the flow of genetic information from DNA to RNA to protein. It is defined as a process in which the information in DNA is converted into a functional product (protein). Steps Involved in Central Dogma Replication Transcription Translation  Central Dogma of life The information content of DNA is in the form of specific sequences of nucleotides. The DNA inherited by an organism leads to specific traits by dictating the synthesis of proteins. Gene expression, the process by which DNA directs protein synthesis, includes two stages: transcription and translation. Genes specify proteins via transcription and translation. The central dogma of biology describes the flow of information from gene sequence to protein product.  An Analogy with Central Dogma When you get to the library, you search through the shelves until you find a book that has a good set of instructions for making a table. The library doesn't have a photocopier, but you came well- prepared, and you whip out your pen and notebook and copy down (or 'transcribe') the instructions. Satisfied, you take your notes and head back home. At home, you have all the wood and tools to make the table. You follow the instructions and make the table, effectively 'translating' the written words into a table which you can use in your room.  An Analogy with Central Dogma Library = Nucleus Books in the library = DNA in the form of chromosome One chapter = One gene (contains instruction for one type of protein) Notebook = Represents RNA, which is a smaller molecule that can move out of the nucleus into the cytoplasm, where proteins are made Home = Cytoplasm Table = One protein product Wood to make the table = amino acids for building proteins  Basic Principles of Replication DNA polymerase In the process of DNA replication, the DNA makes multiple copies of itself. Three major steps;  The opening of the double helix and separation of the DNA strands.  The priming of the template strand.  The assembly of the new DNA segment (nucleotides).  Central Dogma of Life: Transcription RNA Polymerase DNA sequence information is converted to mRNA in a process called transcription.  Steps: 1. The double-stranded DNA molecule is partially unzipped. 2. An enzyme called RNA polymerase copies the gene's nucleotides one by one into an mRNA molecule.  Like DNA, mRNA is made of a particular sequence of nucleotides. 7  Unlike DNA, mRNA has only a single strand, and the base Thymine in DNA is replaced by Uracil in RNA. Very importantly, mRNA is small and can easily exit the nucleus and go to the cytoplasm, where proteins are made.  Basic Principles of Replication DNA Replication https://www.ck12.org/flexi/life-science/dna-structure-and-replication/what-are-the-steps-in-dna-replication/ Basic Principles of Transcription and Translation RNA is the bridge between genes and the proteins for which they code. Transcription is the synthesis of RNA using information in DNA.  Transcription produces messenger RNA (mRNA) Translation is the synthesis of a polypeptide, using information in the mRNA.  Ribosomes are the sites of translation 9 Basic Principles of Transcription and Translation Nuclear envelope Eukaryotic cell DNA TRANSCRIPTION Pre-mRNA RNA PROCESSING mRNA splicing Ribosome TRANSLATION Polypeptide 10  Central Dogma of Life: Transcription RNA polymerase bind with DNA, unzip it, and start synthesis of pre mRNA Pre mRNA: contains both exons and introns Splicing mRNA: contains only exons https://www.genome.gov/genetics-glossary/Transcription 11  Central Dogma of Life: Translation Translation The sequence encoded in the mRNA molecule is decoded and converted to an amino acid sequence in a process called translation.  Steps: 1. After a mature mRNA leaves the nucleus of a cell, it heads for a ribosome in the cell’s cytoplasm where the code it contains can be translated to produce a protein 2. As the strand of mRNA slides through the ribosome, the code is read three nucleotides at a time (called a codon). 3. Each codon specifies one amino acid in the polypeptide chain of a protein which are linked together to form a protein. 12  Central Dogma of Life: Translation DNA DNA template 3 5 strand A C C A A A C C G A G T molecule T G G T T T G G C T C A Gene 1 5 3 TRANSCRIPTION Gene 2 U G G U U U G G C U C A mRNA 5 3 Codon TRANSLATION Protein Trp Phe Gly Ser Gene 3 Amino acid 13 Comparison between translation and transcription Transcription Translation To make RNA copies of To synthesize proteins which are used Purpose individual genes for cellular functions Translation is the synthesis of a protein from an mRNA template. i.e., Transcription is the translating the DNA genetic Definition synthesis of RNA from a information carried by mRNA to DNA template. synthesize proteins. This is the second step of gene expression. Products mRNA Proteins Location Nucleus Cytoplasm 14