We designed a screen to identify conditional mutants of S. cerevisiae in which the secretory system was defective. Suppose we were successful in identifying 12 mutants.
Based on your knowledge of the genetic tools for studying baker's yeast, how would you clone the genes that are mutated in your respective yeast strains? What is an approach to cloning the human orthologs of the yeast genes?

Verified step by step guidance

1. Step 1: Begin by isolating the yeast strains with the identified mutations. Use selective media or temperature-sensitive conditions to ensure that only the mutant strains grow under the conditional environment.
2. Step 2: Perform complementation analysis to determine if the mutations are in the same gene or different genes. This involves introducing wild-type yeast genes into the mutant strains and observing whether the secretory defect is rescued.
3. Step 3: Use a yeast genomic library to clone the mutated genes. Transform the mutant yeast strains with plasmids containing fragments of the wild-type yeast genome and identify the plasmid that rescues the defect. This plasmid will contain the wild-type version of the mutated gene.
4. Step 4: Sequence the rescued gene to identify its nucleotide sequence. Compare this sequence to the yeast genome database to confirm the identity of the gene and its function in the secretory pathway.
5. Step 5: To clone the human orthologs of the yeast genes, use sequence homology analysis. Search human genome databases for genes with significant sequence similarity to the yeast gene. Once identified, clone the human ortholog using PCR or other molecular cloning techniques, and validate its function through expression studies in yeast or human cell lines.

Key Concepts

Gene Cloning Techniques

Gene cloning involves isolating and amplifying a specific gene of interest. Common techniques include using restriction enzymes to cut DNA, ligating the gene into a vector, and transforming the vector into host cells, such as bacteria or yeast. This allows for the replication and study of the gene, facilitating the identification of mutations in the yeast strains.

Conditional Mutants

Conditional mutants are organisms that exhibit a mutant phenotype only under certain environmental conditions, such as temperature or nutrient availability. In the context of S. cerevisiae, these mutants can help identify essential genes involved in specific cellular processes, like the secretory system, by allowing researchers to observe the effects of mutations under controlled conditions.

Orthologs and Functional Conservation

Orthologs are genes in different species that evolved from a common ancestral gene and typically retain the same function. Cloning human orthologs of yeast genes involves identifying these conserved genes through sequence similarity and functional studies, which can provide insights into gene function and disease mechanisms in humans based on findings from yeast models.