Yeast are single-celled eukaryotic organisms that grow in culture as either haploids or diploids. Diploid yeast are generated when two haploid strains fuse together. Seven haploid mutant strains of yeast exhibit similar normal growth habit at 25°C, but at 37°C, they show different growth capabilities. The table below displays the growth pattern Researchers induce fusion in pairs of haploid yeast strains (all possible combinations), and the resulting diploids are tested for their ability to grow at 37°C. The results of the growth experiment are shown below. How many different genes are mutated among these seven yeast strains? Identify the strains that represent each gene mutation.

Key Concepts

Haploidy and Diploidy

Haploidy refers to cells that contain a single set of chromosomes, while diploidy indicates cells with two sets. In yeast, haploid strains can mate to form diploid cells, which can then undergo genetic analysis. Understanding the difference between these two states is crucial for analyzing genetic mutations and their inheritance patterns.

Gene Mutation

A gene mutation is a change in the DNA sequence that can affect an organism's traits. In the context of the yeast strains, mutations may lead to differences in growth capabilities at elevated temperatures. Identifying the specific genes that are mutated among the strains is essential for understanding the genetic basis of their phenotypic variations.

Complementation Testing

Complementation testing is a genetic technique used to determine whether two mutations that produce a similar phenotype are in the same gene or in different genes. By fusing haploid strains and observing the growth of the resulting diploids, researchers can infer the number of distinct mutations and identify which strains represent each gene mutation based on their growth patterns.