@article{mbs:/content/journal/micro/10.1099/00221287-33-3-385, author = "Macdonald, K. D. and Hutchinson, J. M. and Gillett, W. A.", title = "Formation and Segregation of Heterozygous Diploids between a Wild-Type Strain and Derivatives of High Penicillin Yield in Penicillium chrysogenum", journal= "Microbiology", year = "1963", volume = "33", number = "3", pages = "385-394", doi = "https://doi.org/10.1099/00221287-33-3-385", url = "https://www.microbiologyresearch.org/content/journal/micro/10.1099/00221287-33-3-385", publisher = "Microbiology Society", issn = "1465-2080", type = "Journal Article", abstract = "SUMMARY: Heterozygous diploids were produced between a wild-type strain of Penicillium chrysogenum and two strains derived from it. The derived strains had been isolated after several and latterly divergent selection steps, selection being made at each step for higher penicillin yield. The diploids had penicillin titre values near that of the wild-type strain so that mutations for increased penicillin production which had been accumulated in the derived strains appeared in the main to be recessive. First-order segregants isolated from the heterozygous diploids were in each case predominantly of one phenotype.", }