Yes, yeast have sexes, although they aren't quite the same as male and female in animals. Yeast have mating types that function similarly to sexes.
Yeast Mating Types Explained
Instead of having distinct male and female genders, yeast typically have two "mating types." These mating types are often designated as:
- a: One mating type.
- α (alpha): The other mating type.
These mating types are determined by different genes.
How Yeast "Sex" Works
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Signaling: Yeast cells of type a secrete a mating factor called a-factor, and cells of type α secrete α-factor. These factors bind to receptors on cells of the opposite mating type.
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Cell Cycle Arrest: The binding of the mating factor causes the cells to stop growing and preparing to divide.
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Shmooing: The cells then change shape, developing a "shmoo," which is a projection toward the highest concentration of the mating factor.
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Fusion: The a and α cells fuse together, forming a diploid cell.
Differences from Animal Sexes
While yeast mating types are analogous to sexes, there are key differences:
- No Morphological Differences: a and α cells don't have obvious morphological differences like sperm and eggs.
- Diploid Formation: The fusion of a and α cells creates a diploid cell, whereas in animals, sex results in a diploid zygote from haploid gametes.
The Role of Genes
The MAT (mating type) locus on chromosome III determines the mating type of the yeast cell. This locus contains different genes depending on whether the cell is type a or type α. These genes control the production of mating factors and receptors, as well as other proteins involved in the mating process.
