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Transcription and Translation © copyright- All rights reserved www.cpalms.org Standard(s): • SC.912.L.16.5 Explain the basic processes of transcription and translation, and how they result in the expression of genes. Learning objectives: • Students will compare and contrast the processes of transcription and translation. • Students will model how transcription and translation lead to the expression of genes. DNA RNA transcription translation Amino acid Protein Codon/ anticodon Guiding question: How are proteins made according to the code in DNA? cell chromosome nucleus DNA gene Transcription Transcription Transcription- is the process in which DNA is unzipped in a particular gene to create a copy (mRNA) that will code for a specific protein needed by the cell/ living organism. • DNA makes RNA Transcription • RNA polymerase “unzips” DNA • RNA polymerase copies the nucleotide bases from DNA to mRNA according to the base paring rules in the 5’ to 3’ direction (adds to the 3’ end) – C pairs with G, A pairs with T in DNA (and U in mRNA) Transcription • Once completed, the newly formed mRNA is sent to the ribosome complex (in the cytoplasm) to make a protein *Went from DNA to mRNA!! Transcription in a nutshell Occurs inside the nucleus Specific gene is copied into mRNA (messenger) One mRNA codes a single protein End result is the code for a single protein Translation Translation- is the process of changing the mRNA code coming from the DNA into amino acids that will form the protein needed by the cell/ living organism. • RNA makes Protein Translation • mRNA bind with a ribosome forming a complex in which different tRNA brings an amino acid by matching the mRNA according to the base paring rules for RNA. • mRNA and tRNA (transport) function in triplets called codon and anticodon respectively – Work like a key and lock system. Codon • Each tRNA molecule has a triplet anticodon on one end and an amino acid attachment site on the other Amino acid attachment site Anticodon Figure 10.11B, C • mRNA, a specific tRNA, and the ribosome subunits assemble during initiation Large ribosomal subunit Initiator tRNA P site A site Start codon mRNA 1 Figure 10.13B Small ribosomal subunit 2 Amino acid Polypeptide A site P site Anticodon mRNA 1 Codon recognition mRNA movement Stop codon New peptide bond 3 Translocation 2 Peptide bond formation Figure 10.14 Translation • In protein production there are codons that will indicate to the ribosome when to start and when to end. • Once the chain of up to several hundreds of amino acids is completed, the process stops and the protein gets sent to the endoplasmic reticulum to be packed and released. • The order of amino acids determines the shape and function of the newly formed protein. Gene 1 Gene 3 DNA molecule Gene 2 DNA strand TRANSCRIPTION RNA Codon TRANSLATION Polypeptide Figure 10.7 Amino acid Virtually all organisms share the same genetic code “unity of life” Second Base C U UUU UUC UUA UUG C CUU CUC CUA CUG A AUU AUC ile AUA AUG met (start) ACU ACC ACA ACG G GUU GUC GUA GUG GCU GCC GCA GCG phe leu leu val UCU UCC UCA UCG CCU CCC CCA CCG A ser UAU UAC UAA UAG pro CAU CAC CAA CAG thr AAU AAC AAA AAG ala GAU GAC GAA GAG G tyr stop stop his gln asn lys asp glu UGU UGC UGA UGG CGU CGC CGA CGG AGU AGC AGA AGG GGU GGC GGA GGG cys stop trp arg ser arg gly U C A G U C A G U C A G U C A G Third Base First Base U mRNA codon chart Alanine : Ala Arganine: Arg Asparagine: Asn Aspartic acid: Asp Cysteine: Cys Glutamic acid: Glu Glutamine: Gln Glycine: Gly Histidine: Hist Isoleucine: Ile Leucine: Leu Lysine:Lys Methionine: Met Phenylalanine:Phe Proline:Pro Serine: Ser Threonine: Thr Tryptophan: Trp Tyrosine:Tyr Valine:Val START: Met Translation in a nutshell Occurs in the cytoplasm Requires a ribosome Ribosomal complex= ribosome + mRNA+ tRNA mRNA contains code for specific tRNA Different tRNA’s bring different amino acids to the ribosome End result is a protein! NUCLEUS CYTOPLASM (ribosome) Central Dogma DNA makes RNA makes Protein • DNA RNA = transcription • RNA Protein= translation How do you go from DNA to the color of your eyes? 3 genes code for eye color Transcription and translation Enzyme (protein) That controls levels of melanin Mutations can change the meaning of genes • Mutations are changes in the DNA base sequence – caused by errors in DNA replication or by mutagens – change of a single DNA nucleotide causes sickle-cell disease Normal hemoglobin DNA mRNA Mutant hemoglobin DNA mRNA Normal hemoglobin Sickle-cell hemoglobin Glu Val Figure 10.16A • Types of mutations NORMAL GENE mRNA Protein Met Lys Phe Gly Ala Lys Phe Ser Ala BASE SUBSTITUTION Met Missing BASE DELETION Met Lys Leu Ala His Figure 10.16B Types of Mutations • • • • Missense (Substitution) Nonsense (substitution) Deletion (frameshift) Insertion (frameshift) •Chromosomal changes can be large or small Deletion Homologous chromosomes Duplication Inversion Reciprocal translocation Nonhomologous chromosomes Figure 8.23A, B