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25 Cards in this Set

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