Determine genotypes and phenotypes expected in progeny
Biology
Question: In the fungus Neurospora (a haploid), the td+ allele is needed for the cells to build the amino acid tryptophan (trp). The mutant allele td- results in an inability of the fungus to make its own trp, so that growth can occur only if tryptophan is supplied in the medium. Another gene, su, assorts independantly of the td gene. Su+ has no effect, but su- suppresses the td- phenotype so the cells are able to make trp. Therefore, strains that are td-su- do not require tryptophan for growth. If a td- su- strain is crossed with a genotypically wild-type strain (td+ su+), what genotypes and phenotypes are expected in the progeny, and in what proportions?
