RNA & Protein Synthesis Genes send messages to cellular machinery RNA Plays a major role in process Process has three phases (Genetic) Transcription (Genetic) Translation Protein Synthesis RNA Synthesis (transcription) One gene codes for one polypeptide chain. Each gene is several thousand nucleotide pairs long (DNA). Each gene contains the code for the production of a particular type of mrna. For the genetic code to be translated into synthesis of a particular protein, the DNA code is copied onto a strand of mrna (genetic transcription). Transcription Strand of mrna forms that is complementary to a portion of DNA. Triplet of mrna is termed a codon. Codon - contains a triplet code. Every three bases represents one amino acid.
Transcription (codons) Genetic Transcription RNA-polymerase breaks weak hydrogen bonds between paired bases of DNA. Regulatory molecules binding the gene, activating the gene. Double stranded DNA separates at region to be transcribed. One freed strand of DNA serves as guide. Freed bases pair with complementary RNA nucleotide bases forming mrna. mrna detaches. Transcription converts DNA code into mrna format
Translation Translation is the synthesis of a polypeptide (protein synthesis) under the direction of an mrna molecule. Transfer RNA molecules bring amino acids to the ribosomes. Anticodon is triplet complementary to an mrna codon. Polypeptide synthesis requires three steps. Initiation. Elongation. Termination. Protein Synthesis Each mrna passes through ribosomes forming a polyribosome. Association of mrna with ribosomes is needed for genetic translation. Translation: Production of specific protein according to code contained in mrna base sequence. Protein Synthesis (conti nued) Each mrna contains hundreds of nucleotides arranged in sequence determined by the complementary base pairing with DNA. Codon: Each 3 bases (triplet) is a code word for a specific amino acid.
Protein Synthesis (conti nued) Transfer RNA Translation of the codons accomplished by trna and enzymes. trna bends on itself, making an anticodon (3 nucleotides that are complementary to codon of mrna). Synthetase enzymes join specif ic amino acids to the ends of trna within a given codon. Formation of a Polypeptide Anticodons of trna binds to mrna codons. Each trna carries a specific amino acid. trna bring amino acids close together. Amino acid detaches from trna. Enzymatically this amino acid is transferred to the amino acid on the next trna. Polypeptide chain grows. Interactions between amino acids cause chain to twist and fold forming secondary and tertiary structure.
Anticodon-Codon Base Pairing Translation of mrna Protein synthesis.exe
Protein Synthesis (conti nued) Protein Synthesis & Gene Expression Expression = proteins built from a gene s information Structure and Function of Proteins. Proteins are composed of amino acids. Proteins differ because the number and order of their amino acids differ.
Gene Expression Review DNA triplet codes for a specific amino acid. During transcription, a segment of DNA serves as a template for mrna. Messenger RNA carries a sequence of codons to the ribosomes. Transfer RNA molecules have anticodons complementary to mrna codons. Linear sequence of mrna codons determines order amino acids are incorporated into a protein. Functions of ER and Golgi Complex Proteins to be secreted by the cell are synthesized by mrna-ribosome complexes located on granular ER. Proteins enter the cisternae, and are modified. Leader sequence of amino acids is attracted to membranes of ER. Once proteins are in cisternae, the leader sequence is removed. Enzymatic removal of regions in protein, alter structure. Functions of ER and Golgi Complex (conti nued) Secretory proteins are transported to Golgi complex. Further modified, packaged in vesicles, and secreted.