This pedigree traces the inheritance of two characteristics... color blindness and a deficiency in glucose 6-phosphate dehydrogenase. The dark shading means the presence of the mutant phenotype. Give the genotypes of the numbered individuals. Note: What occurred to produce the genotype in #4? Color blindness is a sex-linked gene. What can you say about the glucose 6-phosphate enzyme deficiency? Think about your answer and then scroll down the window to see if you were correct in your assumptions.
Female #1 is heterozygous for the enzyme deficiency while male #3 has the color blind deficiency. Female #2 is heterozygous for both genes which, by their mode of inheritance must lie on diffrent chromosomes. However crossing-over in female #2 produced a chromosome carrying both genes which then appear together in male
#4. To cross over in this fashion means that the enzyme deficiency must be on the X chromosome and therefore sex-linked along with the color blind gene.
