BIO2581B - Tutorial 3 - Section 22

In a genetic study to identify mutations that confer resistance to a new antibiotic in a bacterial population, which approach would be most appropriate?

• A) A genetic screen, where all bacteria are exposed to a mutagen and then grown in the absence of the antibiotic to look for resistant mutants.
• B) A genetic selection, where bacteria are exposed to a mutagen and then grown on a medium containing the antibiotic, so only resistant mutants survive.
• C) A genetic screen, where a single bacterium is mutagenized and observed for antibiotic resistance before and after exposure to the antibiotic.
• D) A genetic selection, where bacteria are grown on a medium without the antibiotic, and the growth rate is compared to that on a medium with the antibiotic.
• E) None of the above

Your friend is performing a genetic screen on yeast cells to look for genes that are responsible for synthesis of proline. He finds 50 mutant yeast cells that can grow on media including proline and can’t grow on media not including proline. Therefore, they are auxotrophic for proline and have mutations in genes responsible for synthesis of proline. He then concludes that his findings suggest that there are 50 genes responsible for the synthesis of proline. Why is his claim incorrect?

• You can have multiple independent alleles on the same gene
• There are 50 cells responsible for the synthesis of proline
• Genetic screens often identify genes with diverse functions unrelated to the observed phenotype
• Proline synthesis is typically controlled by a small number of genes, not a large number
• His claim is entirely correct

which scenario describes how epistatic genes and their function in a switch regulation pathway?

• a) Gene 1 regulates gene 2, which in turn controls the activity of gene 3
• b) Gene 3 influences the expression of gene 1, and the combined action of gene 1 and gene 3 determines the function of gene 2
• c) Gene 2 directly regulates gene 1 and gene 3 (no specific order)
• d) Gene 3 regulates gene 2, but gene 1 functions independently
• no

Which of the following is an example of selection in forward genetics?

• a) Mutagenizing a sample of bacteria cells and plating them on a medium with all the sufficient nutrients to survive and searching for colonies that are yellow
• b) Using CRISPR to remove a particular gene of E. coli cells and plating them on a medium with all the sufficient nutrients to survive and seeing what happens to the cells
• c) Mutagenizing a sample of yeast cells and plating them on a medium containing penicilin and searching for colonies that survived
• d) Using CRISPR to remove a particular gene of E. coli cells and plating them on a medium with all the sufficient nutrients to survive and searching for colonies that are green
• e) Mutagenizing a sample of yeast cells and plating them on a medium with all the sufficient nutrients to survive and searching for colonies that survived

The YFG gene is responsible for the proper development of arms in Drosphila. To induce the ectopic transformation of a drosphila structure into an arm, which driver gene based on the expected changes?

• a) CBR4: expressed in the arms; homeotic selector gene
• b) ABR3: expressed in the thorax and wing; homeotic selector gene
• c) Cdp: expressed in the arms; segment polarity gene
• d) VPh9: expressed in the arms; gap gene
• Na

Scientists are investigating a recently discovered plant protein that they believe controls flower development. To study its role, they need a temporary, RNA-based method to silence the protein in plant cells, minimizing disruptions to the genome. Which option is most appropriate for this situation?

• a) miRNA
• b) transposon-mediated transformation
• c) siRNA
• d) viral-mediated transformation
• e) CRISPR

A researcher tried to study a specific gene in plants that is responsible for its leaves growth. He wants to silence the specific gene to understand its impact on the phenotype. He wishes to use an RNA-mediated gene silencing method. Which method should he use for this purpose?

• siRNA
• miRNA
• CRISPR
• Forward genetics
• None of the above

The Hibiscus is a tropical flower that come in a variety of colours including white, pink, red, blue, orange, peach, yellow and purple. The genotypes and associated phenotypes for some of these flowers are as follows: ssgg: white SSgg: pink Ssgg: pink SSGG: blue-purple SSGg: blue-purple SsGg: blue-purple Based on this information, what would the phenotype of a Hibiscus of the genetype SsGG be and why?

• white because G is epistatic to S
• pink because S is epistatic to G
• pink because G is epistatic to S
• purple because S is epistatic to G
• purple because G is epistatic to S