ch.17 textbook questions – Flashcards
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Distinguish between the cis-acting regulatory elements referred to as promoters and enhancers
PROMOTERS
answer
-conserved DNA sequences that influence transcription from the "upstream" side (5') of mRNA coding genes.
-usually fixed into position and within 100 base pairs of the initiation site for mRNA
-i.e.: TATA, CAAT, and GC boxes
question
Distinguish between the cis-acting regulatory elements referred to as promoters and enhancers
ENHANCERS
answer
-cis-acting sequences of DNA that stimulate the transcription from most promoters.
-position need not be fixed
-may be significant upstream, downstream, or within that gene being regulated
-may be inverted without significantly influencing its action
-can work on different genes, meaning they are not gene specific
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What is necessary to initiate transcription at a regulated gene?
answer
binding of a transcription factor to its DNA recognition sequence
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What plays a role in initiating transcription at a regulated gene?
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-activators and repressors change the relationship of RNAP II to the transcription complex
-DNA loops bring distant enhancer or silencer elements into proximity with promoter regions of the genes under their regulation
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compare gene regulation in eukaryotes and prokaryotes at the level of initiation of transcription
answer
-differences in basic chromosome structure
-chromosome remodeling
-histone acetylation
-differences in gene structure
-cell structure (nucleus in euk.)
-levels of potential regulation
-genomic aspects (amplification)
-biological contact in terms of multicellular interaction versus single-cell survival
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focused vs. dispersed promoters
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focused: define transcription initiation at a single nucleotide; genes of lower eukaryotes & genes that are highly regulated
dispersed: direct initiation from a number of nucleotides covering a relatively large region; promoter genes
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overview of how RNA induced gene silencing achieved through RNA interference (RNAi) and microRNAs (miRNAs)
answer
RNAi begins with a double stranded RNA being processed by a protein called Dicer that, in combo with RISC, generates short interfering RNA (siRNA). Unwinding of siRNA produced an antisense strand that combines with a protein to cleave mRNA complementary sequences. Short RNAs called miRNAs pair with the 3'-untranslated regions of mRNAs and block their translation
question
How would the following mutations affect the transcription of GAL1 gene
a) a deletion within the GAL4 gene that removes the region encoding amino acids 1 to 100
b)a deletion of the GAL3 gene
c)a mutation within the GAL80 gene tht blocks the ability of GAL 80 protein to interact with GAL3p.
d)a deletion of one of the four UASg elements upstream from the GAL1 gene
e)a point mutation in the GAL1 core promoter that alters the sequence of teh TATA box
answer
a)would remove the DNA binding section and not allow trancriptional activation
b)no disruption of the Gal4p/Gal80p complex and no transcription of the GAL4 gene
c)no interaction with the Gal4p/Gal80p complex and no GAL1 trancription
d)reduce transcription of the GAL1 gene
e)reduce transcription of the relevant gene
