Module 4 Practice Exam and Review Flashcards
What role does RNA stability play in gene regulation?
List 3 types of RNA structural elements that can affect the stability of an RNA molecule in eukaryotic cells.
Explain how these elements act to influence RNA stability.
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The stability of mRNA influences gene expression by affecting the amount of mRNA available to be translated. The stability of mRNA is affected by the 5′ cap, the poly(A) tail, the 5′ UTR, the coding section, and sequences in 3′ UTR.
- if RNA is unstable, it will be degraded and unable to use for translation –> amt of protein synthesized depends on amt of available mRNA
- stability controlled by 5’ cap, polyA tail, 5’ UTR, 3’ UTR, and coding region
List 4 levels at which gene control can take place in eukaryotes.
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Alteration of structure, transcription, mRNA processing, RNA stability, translation, Post-translational modification
Define RNA silencing (or interference). Explain how siRNAs arise and how they potentially affect gene expression. How are siRNAs different from the antisense RNA mechanism?
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defn: when siRNA binds to mRNA, stimulating mRNA degradation
- arise from cleavage of dsRNA to make small fragments of ss siRNA
- block gene expression by degrading mRNA before it can be translated
- antisense RNA binds to mRNA too, but physically prevents translation
Process in which cleavage of double-stranded RNA produces small interfering RNAs (siRNAs) that bind to mRNAs containing complementary sequences and bring about their cleavage and degradation.
siRNAs are produced by the cleavage and processing of double-stranded RNA. antisense RNA are small RNA molecule that base pairs with a complementary DNA or RNA sequence and affects its functioning.
RNA silencing is a form of posttranscriptional regulation of mRNA that involves a small interfering RNA molecule formed from the cleavage of double-stranded RNA.
siRNA’s can affect gene expression by binding to complementary sites in mRNA and marking the mRNA for deletion. Antisense RNA binds to the complementary mRNA sequence, keeping it from being transcribed.
RNAi is the formation of 21-25 nucleotide-long siRNAs by Dicer cleavage of double stranded mRNA molecules. These form the RNA-induced silencing complex. The RISC can affect gene expression by inhibiting translation of mRNAs that code for a specific target gene. Antisense RNA mechanism is when a small single strand of RNA binds to the complementary mRNA, physically blocking translation from occurring; RNAi literally chops up the mRNA to prevent translation.
siRNAs arise from transposons, mRNA, and viruses. They are first recognized by a dicer which cleaves the double stranded RNA into short interfering RNA molecules which bind to the RNA induced silencing complex (RISC) which unwinds the RNA. These RNA strands can then bind to complementry strands of RNA and slow their translation down significantly as well as target them for degredation.
antisense RNA:
An RNA molecule (synthesized in vivo or in vitro) with a ribonucleotide sequence that is complementary to part of an mRNA molecule.
Frameshift mutations are caused by the ____ or ____ of one or more nucleotides in DNA.
insertion or removal
b,d
a) No lactose present, no glucose present
b) Lactose present, no glucose present
c) No lactose present, glucose present
d) Lactose present, glucose present
off, high, off, off
______ are complexes where, among other activities, a great deal of RNA degradation takes place.
P bodies
Recent discoveries on causes of fragile-X syndrome, myotonic dystrophy, and Huntington disease indicate what type of genetic alteration?
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not “trinucleotide repeats”
changes in trinucleotide repeats?
When regions around genes become sensitive to the enzyme ______________ this is an indication that those regions are becoming ______________ active.
DNase I, transcriptionally
The __________ stabilizes the 5’ cap, which must be removed before the mRNA molecule can be degraded from the 5’ end.
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NOT Poly(A) tail
Mutations which arise in nature, from no particular artificial agent are called
spontaneous mutations
Which of the following is TRUE for both prokaryotic and eukaryotic gene expression?
RNA polymerase binds to the promoter region to begin transcription.
In what part of the mRNA does degradation generally begin?
at the 5’ end with the removal of the methyl cap
The lac repressor binds to:
lactose and DNA.
__________ mutations produce new traits and are usually dominant.
Gain-of-function
Riboswitches were first discovered in 2002 and have been found in…
In all of the listed organisms:
bacteria
archaea
plants
fungi
Which of the following clusters of terms applies when addressing enhancers as elements associated with eukaryotic genetic regulation?
cis-acting, variable orientation, variable position
Two formal terms used to describe categories of mutational nucleotide substitutions in DNA are called
transversions and transitions
What is the difference between a missense mutation and a nonsense mutation?
missense mutation:
A mutation that changes a codon to that of another amino acid and thus results in an amino acid substitution in the translated protein.
nonsense mutation:
A mutation that changes a codon specifying an amino acid into a Termination codon, leading to premature termination during translation of mRNA.
What is catabolite repression? How does it allow a bacterial cell to use glucose in preference to other sugars?
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catabolite repression =
The selective inactivation of an operon by a metabolic product of the enzymes encoded by the operon.
In catabolite repression, the presence of glucose inhibits (represses) the transcription of genes involved in the metabolism of other sugars.
Because the gene expression necessary for utilizing other sugars is turned off, only enzymes involved in the metabolism of glucose will be synthesized.
Operons that exhibit catabolite repression are under the positive control of catabolic activator protein (CAP).
For CAP to be active, it must form a complex with cAMP.
Glucose affects the level of cAMP.
The levels of glucose and cAMP are inversely proportional—as glucose levels increase, the level of cAMP decreases. Thus, CAP is not activated.
Name 6 different levels at which gene expression might be controlled.
- Regulation of Transcription
- Regulation of Splicing and Processing.
- Regulation of Transport
- Degradation of mRNA
- Regulation of Translation
- Modification and Activity of Protein
(1) Alteration or modification of the gene structure at the DNA level.
(2) Transcriptional regulation.
(3) Regulation at the level of mRNA processing.
(4) Regulation of mRNA stability.
(5) Regulation of translation.
(6) Regulation by post-translational modification of the synthesized protein.
Degradation of a eukaryotic mRNA is generally preceded by shortening of the _____________.
Poly(A) tail
Mutations in the promoter region of the b-globin gene indicate that some areas are more sensitive than others. When mutations occur in consensus sequences (modular elements such as GC box, CAAT box, TATA box), transcription ________________.
decreases
telomeres
highly repetitive DNA
The __________ is a type of _________ protein that binds to a region of DNA in the promoter of a gene called the _________ and prevents transcription from taking place.
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The REPRESSOR is a type of REGULATOR protein that binds to a region of DNA in the promoter of a gene called the OPERATOR and prevents transcription from taking place.