Section 23 Quiz

Which option below is true regarding siRNA and miRNA?

• miRNAs usually have the exact complementarity with their target RNA
• siRNAs usually have the exact complementarity with their target RNA
• siRNAs supress gene expression by inhibiting translation
• miRNAs supress gene expression by degrading mRNA
• None of the above are true

Which of the following is correct?

• Forward genetics starts with a known gene/phenotype, while reverse genetics induces random mutations and screening for phenotypic changes
• Forward genetics is more suitable for haploid organisms, while reverse genetics is more suitable for diploid organisms
• Forward genetics crosses individuals to create heterozygous mutants, while reverse genetics directly mutates the DNA of interest
• Forward genetics is more suitable for diploid genetics to identify recessive alleles, while reverse genetics is more suitable for studying the effects of known mutations
• Forward genetics allows for the direct manipulation of specific genes, while reverse genetics relies on variation to study genes

In a switch regulation pathway controlling flower color in a certain plant species, gene A produces a pigment precursor, gene B activates the conversion of the precursor into the actual pigment, and gene C acts as a switch, turning on gene A and subsequently gene B. If a loss-of-function mutation in gene C leads to the overexpression of both genes A and B, what is the expected phenotype when this mutation is combined with a loss-of-function mutation in gene A?

• Increased pigment production
• Decreased pigment production
• No change in pigment production
• Flower unable to develop
• No pigment production

A made up bacteria named Fonella has a loss-of-function mutation in its methylase protein production. When infected by a virus, the Fonella restriction enzyme will _ X _ the DNA of the virus, and will _ Y _ its own Genomic DNA because it _ Z _ methylated.

• Cut up; cut up; is
• Not cut up; not cut up; is not
• Cut up; not cut up; is not
• Cut up; cut up; is not
• Not cut up; cut up; is

Which of the following is NOT true for miRNA, siRNA, and CRISPR?

• a) A complex induces double-stranded breaks at specific loci in genomic DNA.
• b) They are RNA-mediated methods for alteration of gene activity.
• c) Can be used in systematic genomic screens.
• d) The above 3 process are triggered by DNA/RNA, to which some complex repsonds by degrading the DNA/RNA.
• e) Complex between cleaved fragment and other factors form that recognizes sequences in the DNA/RNA

Which of the following statements is true about the mechanism of siRNA?

• siRNA mechanism starts with single-stranded RNA
• The protein carboxypeptidase cleaves the RNA into small fragments
• For the activation of the silencing complex, other factors and proteins involved in RNA binding bind to the complex, AGO, and Dicer are NOT needed
• If there is no complex formed with Argonaute protein, the siRNA mechanism will not work
• Dicer cleaves dsRNA into large nucleotide fragments

Which of the following statements accurately describes the genetic hierarchy involved in Drosophila segmentation?

• Maternal coordinate genes regulate the expression of zygotic gap genes, which in turn control the development of large domains in body plan.
• Zygotic gap genes directly determine the anterior-posterior axis and specify the number of segments that will form.
• Segment polarity genes activate the expression of homeotic selector genes, which define the structures of specific segments.
• Homeotic selector genes are the first genes expressed from the zygotic genome and regulate the expression of maternal coordinate genes.
• Pair rule genes are transcription factors that pattern the structure of every segment and regulate the expression of zygotic gap genes.

If you are applying reverse genetics on a gene, it often requires being able to reintroduce a mutagenized copy of the gene back into the organism. Often times the DNA doesn't get reintroduced. If you wanted to have the highest chance of reintroducing this mutagenized DNA into the organism, which method would you use?

• Transformation
• Transposon mediated transformation
• Injecting DNA
• Homologous recombination
• Functional complementation

How is the PAM sequence used as a specific tool by Cas9 to cut only the foreign DNA and not the genomic DNA?

• The PAM sequence is only used by Cas9 to attach to viral RNA sequences, not DNA
• Cas9 uses RNA as a guide to specifically avoid cutting genomic DNA, independent of the PAM sequence
• The PAM sequence contains more bits of information than the minimum information necessary to find a specific sequence in the human genome
• The PAM sequence allows the single-stranded DNA to form a loop structure which is recognized and cut by Cas9
• The PAM sequence binds transcription factors which are recognized by Cas9

Choose the statement that best describes the difference between siRNA (small interfering RNA) and miRNA (microRNA) with respect to their mechanisms during gene expression.

• Both miRNA and siRNA result in the cleavage of the gene; mediating RNA degradation.
• Both siRNA and miRNA regulate gene expression by inhibiting translation or promoting mRNA degradation.
• siRNA mainly inhibits translation by binding to imperfect complementarity while miRNA induces cleavage by binding to perfect complementarity.
• siRNA mainly induces cleavage by binding to perfect complementarity while miRNA inhibits translation by binding to imperfect complementarity.
• siRNA and miRNA are both proteins involved in transcriptional regulation of genes as they have direct interaction with DNA sequences.