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25 Cards in this Set
- Front
- Back
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The expression of genes is regulated by regulating _________.
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Transcription
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How is transcription regulated in eukaryotes?
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A protein attaches to the promoter either blocking or stimulating transcription.
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How is transcription regulated in prokaryotes?
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Prokaryotes adjust their transcription rates according to their immediate environment.
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What is the purpose of gene control?
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To maintain homeostasis.
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What is the most common form of gene control?
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Transcriptional control.
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How is a DNA strand read without unwinding it?
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Proteins bind to the outside of the double helix on the major groove.
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What parts of the nucleotides protrude from the major groove?
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Hydrophobic methyl groups, hydrogen atoms, hydrogen bond donors, and hydrogen bond acceptors.
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What permits the protein to bind to the outside of the major groove?
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DNA-binding/structural motifs.
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What are the four DNA-binding motifs that allow protein binding?
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Helix-turn-Helix, Homeodomain, Zinc Finger, and Leucine Zipper motifs.
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Describe the helix-turn-helix motif.
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One protein segment binds to the major groove, the other butts up against the outside. The two binding sites allow for a greatly strengthened bond.
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Describe the homeodomain motif.
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A helix-turn-helix motif, but surrounded by a region that initiates development stages by binding to switch-point genes.
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Describe the zinc-finger motif.
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Zinc atoms coordinate the DNA binding. The more zinc atoms present, the stronger the bond.
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Describe the leucine zipper motif.
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A leucine zipper is formed when two protein subunits attract at their region of hydrophobic amino acids (usually leucines). It is "Y" shaped.
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How do prokaryotic cells repress their genes according to the environment?
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They have multiple genes in a single gene expression group. Some of the genes code for proteins that restrict the gene.
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How do prokaryotic cells promote their genes according to the environment?
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A transcriptional activator binds to a nearby DNA sequence and enhances the promoter on the gene.
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Is transcriptional control more or less complicated in eukaryotes?
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More complicated.
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What are the two types of factors needed for eukaryotic transcription? Describe them.
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Basal- needed to initiate transcription, but don't increase rate beyond basal rate. Specific- increase rate of transcription.
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What are enhancers?
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Binding sites where transcription factors bind and loop the DNA strand.
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Can transcription factors bind to a promoter on a gene packaged in a nucleosome?
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No, the nucleosome blocks the transcription factors from bind with the promoter.
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What does the DNA methylation of cytosine do?
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It allows a blocking protein to bind to "turned-off" genes, which prevents them from being accidentally activated.
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What is posttranscriptional control like in eukaryotes in general?
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Small RNA molecules recognize and bind to the mRNA, preventing its translation. This is called RNA Interference or Gene Silencing.
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What is the method of posttranscriptional control that involves splicing the exons together in different orders?
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Alternative Splicing.
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What must happen for mRNA to pass through the nuclear membrane?
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It must be recognized by the receptors on the pores.
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What other methods of posttranscriptional control are there?
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Selection of which mRNAs are translated, translation repressor proteins bind to the mRNA preventing translation, or the degradation of mRNA before it reaches the ribosome.
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Who made these flashcards?
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Robert Fromm
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