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Explore the final stage of gene expression - protein synthesis, including amino acid structure, tRNA role, and mutations types like missense and frameshift in this informative guide.
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טרנסלציה השלב האחרון בתהליך התבטאות הגנים – סינטזת החלבונים
ספירת מלאי ספירת מלאי
מבנה חומצה אמינית קבוצת צד
N to C terminal 5’ to 3’
ריבוזומים – קומפלקסים של RNA וחלבון
tRNA • Aminoacyl-tRNA synthetase (20 שונים) • one for each amino acid • NEEDS ENERGY!
64 קומבינציות ל-20 ח. אמינו ו-3 קודונים לטרמינציה
Crick’s Wobble Hypothesis • mRNA 3rd nucleotide can either be U or C • tRNA 1st nucleotide guanine (purine) will still pair with either mRNA pyrimidine uracil or cytosine • Consequence is single tRNA species will bring in same amino acid for both UCC and UCU codons. TR11
סרט טרנסלציה ספירת מלאי למתיונין יש רק קודון אחד לעומת זאת ל-LEU יש 6 קודונים מתוכם 4 קודונים של CUN לקרוא
Disease-Associated Mutations A mutation is a change in the normal base pair sequence Commonly used to define DNA sequence changes that alter protein function
Polymorphism DNA sequence changes that do not alter protein function (common definition, not technically correct) Functional protein Functional protein
G A A G U U U U G G U U G G A U U C G G C C A A A A U U C A A U U Met Met Leu Leu Ala Gln Gln Lys Phe Phe Gly G G G A U A Lys Gly Single nucleotide polymorphisms (SNP) (in the coding sequence) mRNA Protein Normal G G A C Ala Sequence variant mRNA Protein Silent DNA sequence polymorphism סינונימי ולא-סינונימי
G A A G U U U U G G U U G G A U U C G G C C A A A A U U C A A U U Met Met Leu Leu Ala Gln Gln Lys Phe Phe Gly G A A Lys Missense Mutations mRNA Protein Normal mRNA Protein Missense G A G C A C Ala Ser Missense: changes to a codon for another amino acid (can be harmful mutation or neutral polymorphism)
G A A G A U U G G U G U C G C A A U C A U Lys Met Leu Ala Gln Phe Gly G A G U U G G U G U U C G A A U C U C A A Met Nonsense Mutations mRNA Protein Normal mRNA Protein Nonsense Nonsense: change from an amino acid codon to a stop codon, producing a shortened protein
G A G U U G G U G A U C G C A A A U C A U Met Leu Ala Gln Lys Phe Gly U G A G U U G G U G A C G C A A A U C A U Met Lys Leu Ala Frameshift Mutations mRNA Protein Normal mRNA Protein Frameshift Frameshift: insertion or deletion of base pairs, producing a stop codon downstream and (usually) shortened protein Pre-mature stop codon
mutation Missense mutation
Translation II פפטיד – רצף של ח. אמינו חלבון – רצף אחד או יותר של ח. אמינו בעל פעילות ביולוגית
Eukaryotic translation initiation can occur at IRES Lodish Fig 4-38
סרט טרנסלציה Life cycle of mRNA movie
NMD Exon junction complex (EJC)
microRNAs MicroRNAs (miRNAs) are noncoding RNAs of 22 nucleotides that induce post-transcriptional gene silencing through base-pairing with their target mRNAs. More than 1000 miRNAs have been identified in human Each miRNA can regulate hundreds of different mRNA molecules MicroRNAs (miRNAs) play important roles in a broad range of biological processes including development, cellular differentiation, proliferation, and apoptosis
