Intro to Molecular Genetics RNA & Protein Synthesis 3/16/2011

Molecular Basis of Heredity Molecular: studying organisms at the molecular (molecule – like DNA) level Genes are coding pieces of DNA Most genes contain nothing more than instructions for assembling/synthesizing proteins Proteins are each designed to build or operate a specific component of a living cell –Examples: A protein that is important in maintaining bone A protein that produces flower pigment (color) A protein that is involved in the digestion of fat

“Central Dogma” The very general view of how molecular biology “works” is that genetic information is transferred from DNA  RNA  protein In this unit, we will be studying the processes by which DNA information is transferred to RNA and how RNA information is transferred to protein The overall two-step process is called protein synthesis – The two steps are transcription and translation

RNA The structure of DNA did not explain how genes worked The discovery of RNA, another nucleic acid, led to the understanding of how genes are expressed – how the DNA code is put into action (how the DNA code “becomes” a protein) RNA is a “disposable” copy of a part of DNA

RNA & DNA In both DNA and RNA, each nucleotide is made up of a 5 carbon sugar, a nitrogenous base, and a phosphate There are three major differences between the two nucleic acids:

Function of RNA The function of most RNA molecules is protein synthesis – RNA controls the assembly of amino acids into proteins Different types of RNA specialize in different aspects of protein synthesis

Types of RNA Messenger RNA (mRNA) – mRNA carries copies of DNA’s instructions to other parts of the cell Ribosomal RNA (rRNA) – The structure of a ribosome consists of two subunits – These subunits are made up of rRNA and other proteins Transfer RNA (tRNA) – Transfers amino acids to the ribosome to be assembled into proteins

Transcription The process of copying DNA’s information into a molecule of mRNA How is it done?