Genetics 2024 Section 5

Which of the following is NOT involved in reintroduction of DNA into an organism?

• a) Recombinase
• b) Transposition
• c) CRISPR - Cas 9
• d) RNA interference
• e) Dominant selectable marker

What is NOT true about reengineered Cas9 defective for double stranded cuts?

• It can function as an inhibitor of transcription
• It can find and bind to unique sequences in the genome
• It can be used to incorporate exogenous DNA into the genome
• It can function as an activator of transcription
• All are true

Which statement correctly describes a difference between small interfering RNA (siRNA) and microRNA (miRNA) in their mechanism of action for regulating gene expression?

• siRNA and miRNA both bind to a target mRNA and inhibit translation by cleaving the mRNA molecule.
• siRNA and miRNA both bind to a target mRNA and inhibit translation by preventing ribosome assembly.
• siRNA binds to a target mRNA with perfect complementarity and induces cleavage, while miRNA binds with imperfect complementarity and inhibits translation.
• siRNA binds to a target mRNA with imperfect complementarity and inhibits translation, while miRNA binds with perfect complementarity and induces cleavage.
• siRNA binds to a target mRNA through base-pairing interactions with the Argonaute protein, while miRNA binds directly to the ribosome to inhibit translation

You are screening 75 leu auxotrophic yeast mutants for the phenotype that have lost the ability to synthesize leucine. You notice that your colonies grow on the rich medium, however they do not grow on either the +leu or -leu plates. Which of the following statements is true?

• A) There was a mutation within 75 of the genes that caused a complete loss of function
• B) The yeast are auxotrophic for proline
• C) The yeast will take multiple generations to colonize on the leucine plate
• D) Two independent mutant -leu alleles cannot complement each other if they are on opposite genes
• E) Each individual colony on the rich media will have a different set of DNA sequence changes

Q. You are growing a colony of bacteria called N. imaginus. When the bacteria is active and produces infection, the bacteria turns purple. When the bacteria is not active, it turns yellow. You are trying to determine the significance of the gene inf in the bacteria’s role to produce infection. When the gene inf is active, the bacteria will also be active and able to produce an infection. You plate your colonies onto an agar plate and you observe, based on the variants, which colonies are yellow vs. purple. This is an example of:

• Forward genetics using a screen
• Forward genetics using selection
• Reverse genetics using a screen
• Reverse genetics using selection
• There is not enough information to determine this

Musa Acuminata, also known as a banana plant, is being studied by several geneticists to understand its development with hopes of optimizing its size and taste. The developmental genes of interest are BAN-1, which expresses a non-coding RNA that binds to itself (double-stranded), and BAN-12, which codes a mitosis-promoting protein. An important observation made, other than BAN-12 not being expressed, was that the RNA transcript from BAN-12 was shorter after its regulation by the RNA-induced signaling complex. What does this observation tell us about the type of RNA used to negatively regulate the expression of BAN-12?

• a) BAN-12 was not expressed due to the use of siRNA because miRNA is inserted as single-stranded RNA
• b) BAN-12 was not expressed through siNA. This is because the "s" in siRNA stands for "short," meaning the transcript will be shorter.
• c) BAN-12 was not expressed due to the use of miRNA. This is because the RNA-induced ; signaling complex is only present in miRNA
• d) BAN-12 was not expressed due to the insertion of siNA. A shorter RNA transcript implies that the BAN-1 transcript was cleaved and degraded
• e) BAN-12 was not expressed due to miRNA. This is because the sequence length of miRNA is shorter than siRNA