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28 Cards in this Set

  • Front
  • Back

3 Major Classes of RNA

mRNA


rRNA


tRNA

RNA Pol I

Transcribes most rRNA genes

RNA Pol II

transcribes protein coding genes, miRNA, and various other small RNAs

RNA Pol III

Transcribes tRNA, 5S rRNA and various other small RNAs

Structures on ends of Mature mRNA

5' Cap (phosphorylated guanine) and 3' Poly A tail

First Amino Acid in every peptide and codon

Methionine AUG

4 levels of gene expression control

Transcriptional


RNA processing


RNA transport


Translation

Prokaryote mRNA features (4)

No introns


No 5' cap (just modifies methionine)


No Poly A Tail


More likely to be polycistronic

Direction of translation

5' to 3'

3 Binding sites for tRNA in RNA Pol II

A;P;E

What do stop codons code for?

Release Factor

Charged tRNA

has an amino acid at its 3' end



Function of Aminoacyl-tRNA synthetases

Adds amino acids to tRNA

When can Control of gene expression be regulated? (4)

Transcription control


RNA processing control


RNA transport Control


Translational control


Post translational control

4 Methods of Transcriptional control

Accessibility of the gene


Gene silencing by DNA methylation


Transcriptional activators/repressors


Freqeuncy of transcription initiation.

Nucleosome

8 histone proteins (146 bp)

Epigenetics

Heritable changes in gene expression not caused by changes to DNA sequence

2 methods of epigenetic control

DNA methylation


Histone modification

DNA methylation

on Cytosine


Prevents transcription by attracting transcription blocker proteins or by blocking transcription factor binding

Histone acetylation

switches on genes

HAT enzymes

Histone acetyl transferase


add acetyl groups to histones

HDAC enzymes

Histone Deacetylases


repress transcription

HMT enzymes

Histone Methyl transferase


Involved in DNA methylation

3 methods of transmitting expression patterns to daughter cells

Positive feedback loop of transcription regulators


Propagation of condensed chromatin structure


Propagation of DNA methylation state

Combinatorial control of transcription

Groups of regulatory proteins work together to express a gene

Enzyme involved in gene splicing

Spliceosome

trp operon

Tryptophan binds to inactive repressor which activates it


Repressor then binds to operating preventing RNA Pol from binding

lac operon

Lactose binds to active repressor inactivating it allowing RNA pol to bind to promotor


RNA Pol binding is stimulated by CAP which is activated by cAMP produced when glucose levels are low