Question

Three autosomal recessive mutations in yeast, all producing the same phenotype \((m 1, m 2, \text { and } m 3),\) are subjected to complementation analysis, Of the results shown below, which, if any, are alleles of one another? Predict the results of the cross that is not shown-that is, \(m 2 \times m 3\) Cross \(1: \quad m I \times m 2 \longrightarrow P_{1}=\) all wild-type progeny Cross \(2: \quad m I \times m 3 \longrightarrow P_{1}:\) all mutant progeny

Short answer

Answer: Mutations m1 and m3 are alleles of the same gene. The cross m2 x m3 is predicted to result in all wild-type progeny.

Step-by-step solution

Interpret results of Cross 1

The first cross results in all wild-type progeny. This indicates that \(m1\) and \(m2\) complement each other and are most likely not alleles of the same gene.

Interpret results of Cross 2

The second cross results in all mutant progeny. This suggests that \(m1\) and \(m3\) do not complement one another, which means they are alleles of the same gene.

Predict results of Cross 3 (\(m 2 \times m 3\))

Since \(m1\) and \(m3\) are alleles of the same gene, and \(m1\) and \(m2\) complement each other, it is likely that \(m2\) and \(m3\) will interact similarly. Therefore, the cross \(m 2 \times m 3\) should result in all wild-type progeny. In conclusion, \(m1\) and \(m3\) are alleles of the same gene, and the cross \(m 2 \times m 3\) should result in all wild-type progeny.

Key concepts

Autosomal Recessive Mutations

Autosomal recessive mutations occur on the autosomes, which are non-sex chromosomes. These mutations are known as recessive because their effects are only seen when an individual carries two copies of the mutant allele. This means a person must inherit one recessive allele from each parent to express the trait associated with the mutation.

In yeast genetics, understanding these mutations is crucial for studying genetic traits and conditions. Since yeast is a simple, single-celled organism, it serves as an ideal model for examining basic genetic principles, like inheritance and mutation.

When dealing with such mutations, it is important to test whether two individuals (or strains, in yeast) expressing the same phenotype actually have mutations in the same gene. This helps determine if they are alleles of one another.

Complementation Analysis

Complementation analysis is a genetic technique used to determine if two mutations producing the same phenotype are in the same or different genes. If two recessive mutations complement each other, they must be in different genes. This occurs when one mutation provides the function that the other lacks.

During complementation analysis, the mutations are crossed. If the resulting progeny display the wild-type phenotype, it indicates that the mutations complement each other. This tells us that the mutations affect different genes. Conversely, if the progeny are mutants, the mutations likely do not complement each other, suggesting they are alleles of the same gene.

The results from the original exercise illustrate a classic demonstration of this principle, where two mutations, when crossed, resulted in either all wild-type progeny or all mutant progeny, helping to determine their allelic relationship.

Yeast Genetics

Yeast, a model organism in genetic research, offers valuable insights into fundamental genetic processes. Its simple eukaryotic structure and rapid growth cycle make it ideal for genetic studies, such as mutation analysis and complementation tests.

In the context of the exercise, yeast genetics allows researchers to easily identify autosomal recessive mutations and analyze their interactions. This ability to conduct controlled genetic crosses and observe progeny phenotypes provides robust experimental evidence for genetic studies.

Utilizing yeast as a genetic model helps scientists extrapolate findings to more complex organisms. The research conducted with yeast can reveal insights into genetic diseases and highlight genetic interactions that may be pertinent to human health.