It was discovered by alexander fleming in the 1920's that penicillium notatum produced a substance, know as penicillin, which had antibiotic properties. many would consider this to be one of the greatest and most important medical discoveries of all time. penicillium notatum is what type of organism? a) bacteria b) fungi c) protist d) virus

During crossing-over, a. genetic material is exchanged between nonsister chromatids, resulting in new combinations of alleles. b. nonsister chromatids from each homologous chromosome of a tetrad are exchanged, resulting in new combinations of alleles. c. one homologous chromosome of a tetrad is exchanged with another tetrad, resulting in new combinations of alleles. d. sister chromatids from each homologous chromosome of a tetrad are exchanged, resulting in new combinations of alleles. e. genetic material is exchanged between sister chromatids, resulting in new combinations of alleles.