Genetics topic 12

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11 Terms

1
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Attenuation

prokaryotes, cis, transcription

transcriptional terminatory secondary structured formed in 5’ UTR of mRNA when trp-loaded tRNAs are available = terminates transcription

<p>prokaryotes, cis, transcription</p><p>transcriptional terminatory secondary structured formed in 5’ UTR of mRNA when trp-loaded tRNAs are available = terminates transcription</p>
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riboswitches

both prok and euk (not animals), cis, transcription and translation

Signal binds within the secondary structure changing the shape of the 5’ UTR, can either prevent or cause expression

Transcription- in prok and acts as attenuation

Translation- prok or euk and affects accessibility of ribosome’s binding site (5’ cap in euk and shine dalgarno in prok)

<p>both prok and euk (not animals), cis, transcription and translation</p><p>Signal binds within the secondary structure changing the shape of the 5’ UTR, can either prevent or cause expression</p><p>Transcription- in prok and acts as attenuation</p><p>Translation- prok or euk and affects accessibility of ribosome’s binding site (5’ cap in euk and shine dalgarno in prok)</p>
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Antisense RNA (asRNA)

in prok and euk, cis and trans, translation, 50-1,000 bp

cis or trans depends on the source of the asRNA

asRNA complimentary to target gene’s mRNA and binds to it and blocks translation by binding to 5’ end covering shine dalgarno in prok or making 5’ end double stranded in euk preventing binding of ribosome

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microRNA (miRNA)

euk, trans, translation, 21-25 bp

DICER cuts mRNA into miRNA which binds with RISC which binds miRNA to target mRNA in an imperfect binding format resulting in inhibition

<p>euk, trans, translation, 21-25 bp</p><p>DICER cuts mRNA into miRNA which binds with RISC which binds miRNA to target mRNA in an imperfect binding format resulting in inhibition </p>
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siRNA in mRNA

euk, cis, translation, 21-25 bp

DICER cuts mRNA into siRNA which binds with RISC which binds siRNA to target mRNA in a perfect binding format resulting in degradation

<p>euk, cis, translation, 21-25 bp</p><p>DICER cuts mRNA into siRNA which binds with RISC which binds siRNA to target mRNA in a perfect binding format resulting in degradation</p>
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siRNA in DNA

euk, cis, translation, 21-25 bp

DICER cuts mRNA into siRNA which binds with RITS which binds siRNA to target DNA and recruits DNA methyl transferases to methylate the target gene and prevent transcription

<p>euk, cis, translation, 21-25 bp</p><p>DICER cuts mRNA into siRNA which binds with RITS which binds siRNA to target DNA and recruits DNA methyl transferases to methylate the target gene and prevent transcription</p>
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long non-coding RNA (lncRNA)

cis, transcription, 200-100000 bp

is transcribed but do not code for a protein, bind to DNA, mRNA, or proteins, can either increase or decrease expression

Ex. Xist in X inactivation

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How does Xist work

cis acting, 17,000 pb, lncRNA, expressed from one X csome

  1. RNAs wrap arond X csome that will be inactivated

  2. causes the formation of heterochromatin through histone deacetylation and methylation

  3. inactivated x is known as a barr body

<p>cis acting, 17,000 pb, lncRNA, expressed from one X csome</p><ol><li><p>RNAs wrap arond X csome that will be inactivated</p></li><li><p>causes the formation of heterochromatin through histone deacetylation and methylation</p></li><li><p>inactivated x is known as a barr body</p></li></ol><p></p>
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Lyon hypothesis

choice of which x is inactivated is random, solves dosage problem

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dosage compensation in drosophila

a set of proteins only expressed in males bind to the x csome and increases x linked gene expression by histone acetylation

<p>a set of proteins only expressed in males bind to the x csome and increases x linked gene expression by histone acetylation</p>
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dosage compensation in C. elegans

repressor proteins bind to both Xs (two) and repress each about half

<p>repressor proteins bind to both Xs (two) and repress each about half</p>