BIO311C_Spr11_Chapter_17_part 2

BIO311C_Spr11_Chapter_17_part 2 - Gene Expression...

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Gene Expression Figure 17.26 TRANSCRIPTION RNA is transcribed from a DNA template. DNA RNA polymerase RNA transcript RNA PROCESSING In eukaryotes, the RNA transcript (pre- mRNA) is spliced and modified to produce mRNA, which moves from the nucleus to the cytoplasm. Exon Poly-A RNA transcript (pre-mRNA) Intron NUCLEUS Cap FORMATION OF INITIATION COMPLEX After leaving the nucleus, mRNA attaches to the ribosome. CYTOPLASM mRNA Growing polypeptide Ribosomal subunits Aminoacyl-tRNA synthetase Amino acid tRNA AMINO ACID ACTIVATION Each amino acid attaches to its proper tRNA with the help of a specific enzyme and ATP. Activated amino acid TRANSLATION A succession of tRNAs add their amino acids to the polypeptide chain as the mRNA is moved through the ribosome one codon at a time. (When completed, the polypeptide is released from the ribosome.) Anticodon A C A A A U G G U U U A U G U E A Ribosome 1 5 5 3 Codon 2 3 4 5
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Genetic code and translation Chapter 17 (328-331, 337- 342)
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Codons: Triplets of Bases Genetic information is encoded as a sequence of  nonoverlapping base triplets, or codons
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www.wikipedia.org
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Figure 17.5 Second mRNA base U C A G U C A G UUU UUC UUA UUG CUU CUC CUA CUG AUU AUC AUA AUG GUU GUC GUA GUG Met or start Phe Leu Leu lle Val UCU UCC UCA UCG CCU CCC CCA CCG ACU ACC ACA ACG GCU GCC GCA GCG Ser Pro Thr Ala UAU UAC UGU UGC Tyr Cys CAU CAC CAA CAG CGU CGC CGA CGG AAU AAC AAA AAG AGU AGC AGA AGG GAU GAC GAA GAG GGU GGC GGA GGG UGG UAA UAG Stop Stop UGA Stop Trp His Gln Asn Lys Asp Arg Ser Arg Gly U C A G U C A G U C A G U C A G First mRNA base (5 end) Third mRNA base (3 Glu Initiator or start codon: AUG Termination or stop codons: UAA, UAG, UGA Universal genetic code!
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Characteristics of Genetic Code A) Genetic code is almost universal
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B) Genetic code is non-overlapping
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Genetic code is non-overlapping
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C) Genetic code is degenerate
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Many codons are redundant: two or more codons can  code for the same amino acid. Degenerate codons may differ in their third positions
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BIO311C_Spr11_Chapter_17_part 2 - Gene Expression...

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