Tut3/7 Quizziz

What is one common mechanism of RNAi- what is one thing both mechanisms of siRNA and miRNA share?

• Both create complexes with perfect complementarity to the target RNA
• Both involve dicers that create small RNA fragments of 21-25nt that bind to AGO protein
• Both cleave the target RNA
• Both use a genic source of DNA with inverted repeats
• all of the above

Which one of the following is NOT a difference between siRNA and miRNA?

• siRNA have perfect complementarity with their target, miRNA do not
• miRNA has a transgenic origin of dsRNA, while siRNA does not
• miRNA can have multiple targets, while siRNA targets are more specific
• siRNA often cleaves its target, while miRNA does not and instead inhibits translation
• all of the above

A mutation in the eukaryotic gene coding for the Argonaute protein changes the sequence of the expressed mRNA gene, causing the Argonaute protein to become inactive and unable to bind small double-stranded RNA molecules. How are the mechanisms for siRNA and miRNA affected?

• a) The siRNA RISC (RNA-induced silencing complex) forms normally while the miRNA RISC cannot form successfully.
• b) The siRNA RISC would not be able to form and attach to the target RNA sequence while the miRNA RISC forms and attaches to the target RNA sequence, inhibiting translation.
• c) Both the siRNA and miRNA RISCs do not form and the translation of the target RNA sequence continues.
• d) The double-stranded RNA molecules in both the siRNA and miRNA mechanisms are not broken down into smaller fragments.
• e) The miRNA RISC forms properly and continues to cleave target RNA sequences while the siRNA RISC does not form properly and cannot inhibit the target RNA sequence from being translated.

Considering the mechanisms of gene expression regulation, which of the following experimental designs would best determine the functional difference between a gene's wild-type and mutant allele in a mammalian cell line?

• A. Introduce the mutant allele using CRISPR-Cas9, and observe phenotypic changes using forward genetics.
• B. Knockdown the expression of the wild-type allele with siRNA and compare the phenotypic outcomes to cells expressing the mutant allele.
• C. Use miRNA to enhance the expression of the mutant allele and compare cell viability to that of cells expressing only the wild-type allele.
• D. Employ reverse genetics to replace the wild-type allele with the mutant allele via homologous recombination and analyze gene expression profiles.
• E. Simultaneously apply CRISPR-Cas9 to knock out the wild-type allele and use a viral vector to introduce the mutant allele, then assess changes in gene expression and cell function.

You are interested in determining what gene(s) are important in the production of leucine in the Yeast Saccharomyces cerevisiae. What is the best way to do so?

• Generate a random pool of genome variants in the cells then grow the yeast on a plate with leucine rich media and a media that lacks leucine. Select for the colonies that survive in the leucine rich media and doesn't in the media lacking leucine. Determine what genes were mutated in those cells.
• Generate a random pool of genome variants in the cells and grow them on a plate containing leucine rich media and a media that lacks leucine. Select for the cells that survives in the leucine rich solution and in the media lacking leucine. Determine what genes were mutated.
• Grow the cells on a plate with a leucine rich media and a media that lacks leucine. Select the cell that survives in the leucine rich media and in the media lacking leucine. Determine what genes were mutated in those bacteria.
• Treat the cell with CaCl. inject the cell with a plasmic containing an allele that contains the enzyme responsible for the production of leucine. If the cell is able to grow in a solution lacking leucine we know that that is the gene that codes for the enzyme that produces leucine
• Mutate a single base in the genome of the cell using CRISPER CAS9 technology. If the cell is able to grow in a solution lacking leucine we know that that is the gene that codes for the enzyme that produces leucine

Which of the following is true of CRISPR, siRNA and miRNA?

• a) CRISPR and siRNA cause double stranded breaks in the target, where miRNA only does a single strand break
• b) CRISPR and siRNA have one specific target, whereas miRNA can have many
• c) CRISPR and siRNA are of a genic source (encoded in the organism's genome) whereas miRNA comes from a transgenic source (inputted into the organism from elsewhere)
• d) CRISPR and siRNA can be methods of preventing introduction of genetic material from another organism, but miRNA cannot.
• e) CRISPR and siRNA use AGO to form the RISC, while the miRNA does not use AGO.

You are a researcher trying to study antibiotic resistance on bacteria. To do this, you isolated a culture of S aureus and transfer them onto a plate with vancomycin medium. After a while, you found that most of the bacteria were killed by vancomycin in the medium, but a small group survived in the medium, which shows that they are more resistant to vancomycin.What did you perform to achieve your goal of studying antibiotic resistance?

• Selection
• Screen
• Transformation
• None of the above
• CRISPR