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Fatih Mehmet İPEK Biology 4 01040011

Concencus Sequences of Eukaryotic Organisms. Fatih Mehmet İPEK Biology 4 01040011. DNA tamplate carries 2 major concensus sequences present on upstream of -35 and -10bp position. DNA dependent RNA polymerase enzyme’s (r) subunit is able to recognise these cencensus sequenes.

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Fatih Mehmet İPEK Biology 4 01040011

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  1. Concencus Sequences of Eukaryotic Organisms Fatih Mehmet İPEK Biology 4 01040011

  2. DNA tamplate carries 2 major concensus sequences present on upstream of -35 and -10bp position. DNA dependent RNA polymerase enzyme’s (r) subunit is able to recognise these cencensus sequenes. -35 bp position is composed of TTGACA -10 bp is composed of TATAATAAT (that part is known TATA box).

  3. DNA tamplate also carries inverted repeats which is composed of G-C and A-T rich sequences. The resion behind of this is termination of the transcribtion procedure. For instance; 5’ ACT-GGCTCC-AAAA-GGAGCC-AAAAAA 3’ DNA tamplate G-C rich G-C rich A-T rich U U U U mRNA H bonds

  4. Eukaryotic mRNA; Eukaryotic mRNA is monocistronic sequences. Eukaryotic mRNA needs maturation in order to pass the cytoplasm from the nucleus. And maturation involves in 3 steps: • CAP protein must be edded to the 5’ end. • PolyA tail ought to add to the 3’ end of the mRNA. • This polyA tail composed of 50 to 250bp lenght of Adenin base repeats. PolyA polymerase enzyme synthesises that part. This enzyme recognise AAUAAA sequence on the 3’ of mRNA and it will remove bases downstream on the mRNA. Then it adds 50-250 bp of Adenin bases.

  5. 3. Eukaryotic mRNA consists of intronic and exonic sequences. Splicing of intron is applied with spliciosome enzyme which is ribonucleoprotein complex (small nuclear RNA + proteins). This enzyme can recognise introns by certain sequences. 5’ ……(A/C)AGGU(A/G)AUG………………(6 Pyrimidin)CAGG(G/U)…..3’ mRNA EXON INTRON EXON 5’UTR 3’UTR mRNA exon #1 intron exon #2 intron exon #3 Exon #1 Exon #2 Exon #3 5’UTR 3’UTR mRNA

  6. 5’ & 3’ UnTranslated Regions (UTR); The crucial role of the non-coding portion of genomes is now widely acknowledged. In particular, mRNA untranslated regions are involved in many post-transcriptional regulatory pathways. The nontranslated 5`end (leader) is relatively short, usually (but not always) less than 100bp. The length of the nontranslated 3`end (trailer) is often rather longer, sometimes around 1000bp. 5`-UTR sequences were defined as the mRNA region spanning from the cap site to the starting codon (excluded), whereas 3`-UTR sequences were defined as the mRNA region spanning from the stop codon (excluded) to poly(A) starting site. mRNA

  7. 5’ & 3’ UnTranslated Regions of eukariotic mRNAs are known to play a crucial role in: • The 5´-and 3`-UTR Post-transcriptional regulation of gene expression modulating nucleo-cytoplasmic mRNA transport. • Control of mRNA cellular and subcellular localization. • Control of mRNA stability. • Control of mRNA translation efficency. Several regulatory signals have already been identified in 5´-and 3`-UTR sequences, usually corresponding to short oligonucleotide tracts, also able to fold in specific secondary structures, which are protein binding sites for various regulatory protein.

  8. REFERENCES :   • Lewin B, Genes 6.addition • Pesole G, Grillo G, Liuni S, Licciulli F, Mignone F, Gissi G, Saccone C. UTRdb and UTR site:specialized databases of sequences and functional elements of 5`and 3`untranslated regions of eukariotic mRNAs. Update 2002. • Meijer H.A, Thomas A.M control of eukaryotic protein synthesis by open reading frames in 5`-untranslated region of an mRNA. • Pesole G, Grillo G, Larizza A, Liuni S The untranslated regions of eukaryotic mRNAs: structure, function, evolution and bioinformatic tools for their analysis.

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