Ch. 11.4 & 11.5: Transcription & Translation. Objectives: Explain one-gene-one polypeptide hypothesis. Describe the process of transcription. Explain how RNA is edited. Describe how RNA is translated into a protein. Describe how amino acids are coded. Summarize protein synthesis. Vocab.:
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Ch. 11.4 & 11.5: Transcription & Translation Objectives: Explain one-gene-one polypeptide hypothesis. Describe the process of transcription. Explain how RNA is edited. Describe how RNA is translated into a protein. Describe how amino acids are coded. Summarize protein synthesis. Vocab.: Transcription, RNA (ribonucleic acid), mRNA, RNA polymerase, intron, extron, RNA splicing Translation, tRNA, codon, anticodon, Codon, rRNA
One Gene, One Polypeptide Genotype: sequence of nucleotides bases in DNA. Phenotype: Organism traits; based on proteins & protein fxns
Expose bread mold to X-rays (Mutation = Damaged DNA). • Essential enzyme/amino acid cannot be made from damaged DNA. • Mutated mold won’t grow on “minimal” medium that lacks enzyme/amino acid it can’t make. Beadle & Tatum: Research leads to “One gene, one enzyme” “one enzyme” - not accurate. 1 gene = 1 poly-peptide (part of 1 enzyme/protein) Beadle & Tatum Experiment: 9:57 min http://www.youtube.com/watch?v=vP_h08cT5jw
RNA carries DNA instructions to Ribos. Ribosomes make PROTEINS. • RNA: Ribonucleic Acid • Single strand nucleotide • 1. 5-C Sugar: Ribose • Phosphate • Nitrogen base (A, U, G, C) U = Uracil; Replaces T A binds to U; G binds to C
Transcription: DNA --> mRNA • DNA cannot leave nucleus. • DNA nucleotide sequence is converted into mRNA (messenger RNA). • mRNA leaves nucleus --> directs protein synthesis @ ribo. in cytoplasm. http://www.youtube.com/watch?v=983lhh20rGY&feature=related http://www.youtube.com/watch?v=41_Ne5mS2ls
Transcription: RNA Polymerase • Enzyme that links RNA nucleotides together (like DNA polymerase) • Transcribes specific segments of DNA.
RNA SPLICING: Editing mRNA 1. INTRONS removed/spliced • non-coding sequences (junk) • Do not code for amino acids 2. EXONS: • Coding sequences • Translate into amino acids (expressed) Splicing: In eukaryotes mRNA is modified before it leaves nucleus.
Translation: mRNA --> proteins • Based on CODON “language” • 3-bases translate into a CODE for specific amino acids. • Amino acids build polypeptides. Nucleic acids --> Proteins
TRANSLATION Each codon codes for 1 amino acid. Start codons: AUG (start translating) Stop codons: UAA, UAG, UGA Same codes for almost ALL organisms!
Required ATP mRNA Ribosomes tRNA Translation • tRNA: Transfer RNA • Translates codon of mRNA into amino acids. • “Fetches” correct amino acid • Attatches to correct codon. • Has “anti-codon” complement to attatch to codon.
rRNA: ribosome (organelle) 2 subunits snap together. mRNA and tRNA join each other in RIBOSOME. Translation: rRNA (Ribosome) 2 tRNA binding sites where translation happens: P site: Growing polypeptide chain. A site: new amino acid binds
Translation: Elongation Polypeptide chain grows. • Translation begins (AUG) codon • Amino acids are added by tRNA (based on mRNA codons). • Translation ends (UAA, UAG, UGA); stop codon. • Polypeptide released (Goes to E.R. and Golgi for modification)