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In aerobic conditions, do yeast prefer to grow by aerobic respiration or fermentation?
Fermentation- as respiration is efficient but slow.
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What are some features of domesticated yeast?
- Decreased survival in nature, sexual reproduction and off-flavours.
- Increased maltotriose utilisation and genome decay.
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What are the uses of yeast?
- Chocolate, coffee, alcohol (with marmite as a byproduct).
- S. cerevisiae engineered to produce artemisinin.
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Why are yeast good model organisms?
- Small genome that is well characterised.
- Undergo rapid growth and breeding.
- Are easy to manipulate.
- Genes homologous to human genes (closer than E. coli).
- Can host human proteins for experiments.
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What is the life cycle of yeast?
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How do α and a haploid form a diploid cell?
MAT gene has MATα and a MATa alleles, which control expression of pheremones and receptors.
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How do you create and identify auxotrophic strains of yeast?
- Mutagenise the liquid culture (e.g. with UV light), dilute and plate on a rich medium.
- Replica plating to minimal medium.
- Colonies that only grow on rich medium have auxotrophic mutations.
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How do you identify which nutrient (often amino acids) the mutant-strain cannot produce.
Add nutrients one at a time, until the colony can grow.
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What phenotype would be produced by crossing a lysine auxotroph and a wild-type phototroph?
wild-type phototroph. This is because the wild-type allele still allows for the metabolic pathway to produce lysine to occur. I think that's complementation.
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What phenotype would crossing a lysine auxotroph and a methionine auxotroph produce?
Wild-type phenotype, as alleles are on seperate genes.
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What phenotype would be produced by crossing a lysine auxotroph from one colony with a lysine auxotroph from another?
Different colonies so different mutations in biochemical pathway e.g. lys1- and lys2-, so complementation occurs and produces a wild phenotype.
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If diploid yeast exhibiting complementation underwent meiosis, what phenotype would their offspring produce?
For multiple mutations, recombination must be accounted for. Counting this on tetrads allow genetic linkage maps to be made.
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