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Prokaryote gene regulation
Transcription regulators
Eukaryote gene regulation
Post transcriptional control
Membranes
100
The name of a DNA sequence that a repressor binds to.
operator
100
When transcription regulators bind to a specific DNA sequence, amino acids form noncovalent bonds with _____________.
the edges of the nitrogenous bases (base pairing is not disrupted).
100
The name of a DNA sequence that an activator binds and then dramatically increases the rate of transcription.
enhancer
100
True/False, if false explain why A riboswitch is a small RNA that binds to several different mRNAs.
False, a riboswitch is part of a mRNA. It can change conformation if bound to a small molecule. Changing conformation can cause RNA polymerase to fall off, or can block a ribosome from reaching the start codon.
100
A molecule with both hydrophobic and hydrophilic regions is said to be ________________.
Amphipathic
200
True/False, explain why The tryptophan repressor binds to DNA when there is NO tryptophan.
False, the tryptophan repressor binds DNA only after it binds to tryptophan. The repressor is inactive in the absence of tryptophan.
200
True/False, if false explain why Transcription regulators can function as homodimers and as heterodimers.
True, the fact that transcription regulators can function as heterodimers increases the number of specific DNA sequences recognized by a set of transcription regulators.
200
True/False, if false explain why Transcription regulators must bind DNA that is less than 1000 nucleotides away from the promoter.
False, DNA regulatory sequences are often 1000s of nucleotides away from the promoter, in addition to some being close.
200
What are two ways the 5' untranslated region can regulate gene expression?
The 5' untranslated region can be a riboswitch or have a conformation that a repressor protein binds to and blocks the start codon.
200
Fatty acid tails with no double bonds are said to be ___________.
saturated
300
The sugar conditions that result in expression of the Lac operon.
When glucose is absent but lactose is present
300
What are three DNA-binding motifs?
Zinc finger, homeodomain and leucine zipper
300
What is spacer DNA?
It is the 1000s of nucleotides between enhancers and a promotor. Spacer DNA is often partly condensed and partly forms a loop so that enhancers are physically close to promotors.
300
True/False, if false explain why MicroRNAs in a RISC complex bind to mRNAs and keep the mRNA stable.
False, a mRNA is degraded when a miRNA binds to it. The RISC complex has a nuclease that degrades the mRNA.
300
The fluidity of a lipid bilayer ____________ when more lipids are added that have unsaturated fatty acid tails.
increases
400
Imagine a cell that has a mutant Lac repressor that cannot bind to lactose. In the absence of glucose, but presence of lactose, will the Lac operon be expressed? Explain.
No, the Lac operon will not be expressed. The Lac repressor will stay bound to the operator because the repressor cannot bind lactose. Binding to lactose is needed to cause the repressor to come off the DNA.
400
Can transcription regulators help determine the chromatin state of specific regions of DNA? Explain
Yes, but indirectly. Transcription regulators bind to specific DNA sequences. Some regulators recruit, by selective binding, enzymes that modify histone tails, or recruit chromatin-remodeling complexes.
400
Is a transcription regulator that recruits a histone acetylase an activator or a repressor?
activator
400
True/False, if false explain why A miRNA can bind to many different mRNAs
True, miRNAs are short (20-30 nucleotides) and bind by complementary base-pairing. Many different mRNAs, which can be 1000s of nucleotides long, can have the short complementary sequence.
400
True/False, if false explain why The plasma membrane is symmetrical because the lipids are the same in both monolayers.
False, the lipids in each monolayer are different. For example, glycolipids are in the outside monolayer, but lacking in the cytosolic monolayer. The orientation of transmembrane proteins is also asymmetrical, and the outside domains are glycosylated, but not the cytosolic domains.
500
How is the expression of enzymes for tryptophan biosynthesis turned off when tryptophan is present?
When tryptophan is present it binds to a repressor protein, which changes to a conformation that binds to an operator. When the repressor is bound to the operator, the sigma factor and RNA polymerase CANNOT bind to the promoter of the tryptophan operon.
500
Can a transcription regulator influence where in a developing body a particular organ will form? Explain
Yes, a transcription regulator can turn on the expression of many other transcription regulators, which then regulate the expression of 1000s of genes. Such a 'master' regulator, if engineered to be expressed in a different part of the body than normal, can result in an organ forming in the wrong place. The Ey (Pax6) transcription regulator is an example.
500
Is a repressor more likely to recruit a histone acetylase or a histone deacetylase?
histone deacetylase
500
True/False, if false explain why RNAs, such as splicing RNA, ribosomal RNA and miRNAs, are synthesized by transcription.
True, functional RNAs are encoded by genes and are synthesized by transcription.
500
How is a membrane selectively permeable?
The lipid bilayer forms a barrier to the diffusion of charged or polar molecules and transport proteins selectively permit specific molecules to cross the barrier.