Structure of RNA  Structure  Nucleic acid made up of nucleotides  composed of Ribose, phosphate group, and nitrogenous base  Nitrogenous bases  Adenine  Uracil  Cytosine  Guanine  Function  Directs the assembly of proteins based on information it receives from DNA

Types of RNA  Messenger RNA (mRNA)  Single uncoiled chain  Carries genetic information from the DNA in the nucleus to the ribosomes in the cytosol  Transfer RNA (tRNA)  Single chain folded into a hairpin shape  Binds amino acids to mRNA code  Transfers amino acids to the ribosomes to make proteins  Ribosomal RNA (rRNA)  Globular form  Makes up ribosomes

Protein Synthesis  Production of proteins with the aid of all three types of RNA  Amount and kind of proteins that are produced in a cell determine the structure and function of the cell  Involved two main steps  Transcription  Translation

Transcription  Occurs in the nucleus  Information in a region of DNA is transcribed or copied into mRNA  Makes new RNA  RNA polymerase binds to specific segments of DNA called the promoter (Starting point)

 DNA molecule separates in the region where the promoter attaches creating a replication fork  RNA polymerase reads the DNA code one nucleotide at a time from the DNA Template until it reaches the termination signal making the new mRNA molecule  Each combination of three mRNA nucleotides is called a codon  Pre-mRNA has non-coding regions or introns cut out so that mRNA strand contains only coding regions or exons  Point mutations only cause changes in protein structure if codon codes for a different amino acid.

 GCTAATCCG -DNA  CGAUUAGGC-mRNA  RNA MESSAGE IS NOW SENT TO CYTOPLASM TO BE TRANSLATED

Translation  Occurs in the cytoplasm  mRNA leaves nucleus and migrates to a ribosome in the cytosol  tRNA molecules read mRNA codon and translate it into an anticodon  Each anticodon codes for a specific amino acid  Each amino acid is bonded to the preceding amino acid by the ribosome producing a polypeptide chain from the original code taken from the DNA template

COMPUTER REVIEW  Computer Interactive:  DNA & RNA Quiz htm htm Drag & Drop Protein Synthesis  Transcribe and translation a gene  Worksheet Don’t forget DNA & Protein Synthesis Exam Wednesday!

Review How does RNA differ from DNA? What are the roles of mRNA and tRNA in protein synthesis?  Complete RNA Worksheet & Nucleic Acids PSSA Worksheet  Don’t forget Vocabulary Quiz Tomorrow!