Common baker's yeast (Saccharomyces cerevisiae) is normally grown at 37°C, but it will grow actively at temperatures down to approximately 25°C. A haploid culture of wild-type yeast is mutagenized with EMS. Cells from the mutagenized culture are spread on a complete-medium plate and grown at 25°C. Six colonies (1 to 6) are selected from the original complete-medium plate and transferred to two fresh complete-medium plates. The new complete plates (shown) are grown at 25°C and 37°C. Four replica plates are made onto minimal medium or minimal plus adenine from the 25°C complete-medium plate. The new plates are grown at either 25°C or 37°C and the growth results are shown.
Which colonies are prototrophic and which are auxotrophic? What growth information is used to make these determinations? <>
17. Mutation, Repair, and Recombination
Induced Mutations
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Join thousands of students who trust us to help them ace their exams!Watch the first videoMultiple Choice
Which of the following mutations would have the least effect on an individual?
A
4 base pair insertion in an intron
B
Deletion of an exon
C
A nonsense mutation in the last exon of a gene
D
A point mutation in the splice site of an intron
Verified step by step guidance1
Understand the role of introns and exons in gene expression. Introns are non-coding regions that are removed during RNA splicing, while exons are coding regions that are expressed in the final protein.
Consider the impact of a 4 base pair insertion in an intron. Since introns are removed during RNA processing, small insertions in introns often have minimal impact on the final protein product.
Evaluate the effect of a deletion of an exon. Exons are crucial for coding the protein, so their deletion can lead to a loss of important protein-coding information, potentially resulting in a nonfunctional protein.
Analyze the consequences of a nonsense mutation in the last exon of a gene. A nonsense mutation introduces a premature stop codon, which can truncate the protein. However, if it occurs in the last exon, the impact might be less severe as the majority of the protein is already synthesized.
Examine the effect of a point mutation in the splice site of an intron. Splice sites are critical for proper RNA splicing. A mutation here can lead to incorrect splicing, potentially resulting in a dysfunctional protein.
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