TECHNOLOGY FOCUS - BIOTECHNOLOGY - Preferred Method: The method (M1) further comprises introducing the dominant mitochondrial ATP synthase gene mutation into the yeast. The method (M2) further comprises introducing a DNA construct into the transgenic non-respiring yeast lacking the mitochondrial DNA by: stably integrating the DNA construct into a vector; stably integrating the vector into a non-respiring yeast; removing the selectable marker from the construct; and identifying a recombinant yeast that lacks the selectable marker but contains the dominant mitochondrial ATP synthase gene mutation. Preferred Components: In the method (M1), the mitochondrial genome of the transgenic non-respiring yeast lacks a mitochondrial gene comprising COX-1, COX2, COX3 or COB. The dominant mitochondrial ATP synthase gene mutation: is an ATP1-111 mutation that comprises an amino acid sequence of SEQ ID NO: 1 (comprising a fully defined sequence of 545 amino acids as given in the specification) or a nucleic acid sequence of SEQ ID NO: 2 (comprising a fully defined sequence of 1638 nucleotides as given in the specification); and has a first repetitive DNA sequence operably linked immediately 5' to the dominant mitochondrial ATP synthase gene mutation, and a second repetitive DNA sequence operably linked immediately 3' to the dominant mitochondrial ATP synthase gene mutation. The transgenic yeast (Y1) further comprises the dominant mitochondrial ATP synthase gene mutation that is stably integrated into the transgenic non-respiring yeast. In the DNA construct, the selectable marker is operably linked to a third repetitive DNA sequence 5' to the selectable marker, where the selectable marker is also operably linked to the third repetitive DNA sequence 3' to the selectable marker. The first repetitive DNA sequence comprises a sequence of SEQ ID NO: 3 (comprising a fully defined sequence of 200 nucleotides as given in the specification). The second repetitive DNA sequence comprises a sequence of SEQ ID NO: 4 (comprising a fully defined sequence of 200 nucleotides as given in the specification). The third repetitive DNA sequence comprises a sequence of SEQ ID NO: 5 (comprising a fully defined sequence of 200 nucleotides as given in the specification). The non-respiring yeast (Y2) lacks a CAT5 nuclear gene. In the transgenic non-respiring yeast (Y3), a first copy of CAT5 gene has been deleted from the transgenic non-respiring yeast, and a second copy of CAT5 gene has been deleted from the transgenic non-respiring yeast. EXAMPLE - No suitable example given.