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intron classes distribution PowerPoint Presentation
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intron classes distribution

intron classes distribution

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intron classes distribution

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    1. Intron Classes & Distribution Group I - organelles, nuclear rRNA genes of certain eukaryotes, bacteria (>1500) Group II - organelles, bacteria, archaea (> 1000) Nuclear mRNA (NmRNA) - ubiquitous in eucaryotes Nuclear tRNA- some eucaryotes

    2. tRNA splicing in two enzymatic steps. Group II and NmRNA splicing related.tRNA splicing in two enzymatic steps. Group II and NmRNA splicing related.

    4. Protein factors forGroup I & Group II Introns 2 types (based on genetic location) Intron-encoded - promotes splicing of the intron that encodes it Nuclear-encoded - for organellar introns - identified in fungi (for mito. introns)

    6. Intron Homing the invasion of an intron-minus gene/allele by the intron from an intron-plus allele. Catalyzed by a protein encoded by the mobile intron.

    16. Chlamydomonas nivalis (augustae)

    17. Do ribozymes show evidence of biochemical adaptation to low temperature? Ribozymes have not been characterized from psychrophiles.

    18. Many organisms are highly adapted to environmental temperature Psychrophiles (< 20?C) Mesophiles (~ 20-35?C) Thermophiles ( ~35-70?) Hyperthermophiles ( > 70-110?C)

    19. Protein enzymes show evidence of adaptation to low temperature Enzymes from psychrophilic organisms: usually have a lower temperature optimum than their mesophilic counterpart are typically more thermolabile are usually more efficient catalysts are likely more flexible

    25. Adaptation in the psychrophiles intron ribozymes? The C. nivalis homologues are much smaller than the reinhardtii introns (lack the ORFs), and are a little more A-T rich. Self-splicing of the C. nivalis rRNA intron (Cn.LSU) is more thermosensitive than that of Cr.LSU. The temperature optima for self-splicing of the Cn.LSU and Cr.LSU introns are similar. The Cn.psbA intron does not self-splice, though it is autocatalytic.

    30. Self-splicing of psbA1 pre-RNAs under optimized conditions: 30 mM MgCl2, 1.3 M NH4Cl, pH 7.5 - not stimulated by spermidine or by a denaturation-renaturation cycle Self-splicing was improved by deleting most of the ORF, and using pre-RNAs directly from transcription reactions, suggestive of a role for folding during transcription. Self-splicing of psbA1 pre-RNAs under optimized conditions: 30 mM MgCl2, 1.3 M NH4Cl, pH 7.5 - not stimulated by spermidine or by a denaturation-renaturation cycle Self-splicing was improved by deleting most of the ORF, and using pre-RNAs directly from transcription reactions, suggestive of a role for folding during transcription.

    33. Assay with polyrA/oligodT; RT spec. activity= 0.015-0.085 pmoles/min/pmole protein, Similar to AMV (0.0177 w/same units) Assay with polyrA/oligodT; RT spec. activity= 0.015-0.085 pmoles/min/pmole protein, Similar to AMV (0.0177 w/same units)

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