Basic Principles of Transcription and Translation - Computer ...

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5′ Protein-coding segment Polyadenylation signal 3′ G P P P AAUAAA AAA… AAA 5′ Cap 5′ UTR Start codon Stop codon 3′ UTR Poly-A tail RNA processing addition of the 5’ cap and poly A tail. Enzymes modify the two ends of a eukaryotic pre mRNA molecule. The modified ends may promote the export of mRNA from the nucleus and they help protect the mRNA from degradation. When the mRNA reaches the cytoplasm the modified ends in conjunction with certain cytoplasmic proteins facilitate ribosome attachment. The 5’ cap and poly A tail are not translated into protein, nor are the regions called the 5’ untranslated regions (5’ UTR) and 3’ untranslated regions (3’ UTR) Split Genes and RNA Splicing • Most eukaryotic genes and their RNA transcripts have long noncoding stretches of nucleotides that lie between coding regions • These noncoding regions are called intervening sequences, or introns • The other regions are called exons because they are eventually expressed, usually translated into amino acid sequences • RNA splicing removes introns and joins exons, creating an mRNA molecule with a continuous coding sequence
5′ Exon Intron Exon Intron Pre-mRNA 5′ Cap 1 30 31 104 105 Exon 3′ Poly-A tail 146 Coding segment Introns cut out and exons spliced together mRNA 5′ Cap Poly-A tail 1 146 5′ UTR 3′ UTR RNA processing: mRNA splicing. The RNA molecule shown here codes for β globin one of the polypeptides of hemoglobin. The numbers under the RNA refer to the codons. β globin is 146 amino acids long. The β globin gene and its pre mRNA transcript have three exons corresponding to sequences that will leave the nucleus as RNA. (The 5’ UTR and 3’ UTR are parts of exons because they are included in the mRNA however they do not code for protein). During RNA processing the introns are cut out and the exons are spliced together. In many genes the introns are much larger relative to the exons than they are in the β globin gene. The mRNA is not drawn to scale. In some cases, RNA splicing is carried out by spliceosomes Spliceosomes consist of a variety of proteins and several small nuclear ribonucleoproteins (snRNPs) that recognize the splice sites
Page 1 and 2: The Flow of Genetic Information Th
Page 3 and 4: TRANSCRIPTION DNA mRNA (a) Bacteria
Page 5 and 6: The Genetic Code How are the instr
Page 7 and 8: Cracking the Code All 64 codons we
Page 9 and 10: Molecular Components of Transcripti
Page 11 and 12: RNA Polymerase Binding and Initiati
Page 13: Eukaryotic cells modify RNA after t
Page 17 and 18: The Functional and Evolutionary Imp
Page 19 and 20: Polypeptide Trp Phe Ribosome Amino
Page 21 and 22: Amino acid P P P ATP Adenosine Amin
Page 23 and 24: Building a Polypeptide The three s
Page 25 and 26: The elongation cycle of translation
Page 27 and 28: Growing polypeptides Completed poly
Page 29 and 30: Polypeptide synthesis always begins
Page 31 and 32: Type of RNA Small nucleolar RNA (sn
Page 33 and 34: RNA polymerase RNA polymerase Polyr
Page 35 and 36: Individual bacteria respond to envi
Page 37 and 38: Eukaryotic gene expression can be r
Page 39 and 40: CYTOPLASM mRNA in cytoplasm Degrada
Page 41 and 42: Histone tails DNA double helix Amin
Page 43 and 44: Epigenetic Inheritance Although th
Page 45 and 46: The Roles of Transcription Factors
Page 47 and 48: Mechanisms of Post-Transcriptional
Page 49 and 50: Initiation of Translation The init
Page 51 and 52: Noncoding RNAs play multiple roles
Page 53: Chromatin Remodeling and Silencing

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