Question

a fruit fly, a white eyed XXY female is mated to a red eyed XY male. The female progeny would be (A) All red eyed (B) All white eyed (C) Mainly red eyed with a few white eyed (D) Mainly white eyed with a few red eyed ​

Answer 1

The cross of white eyed female with red eyed male gives red eyed females and white eyed males. Rarely this cross may give all white eyed females and red eyed males. This results from non-separation of two homologous X chromosomes during anaphase I of meiosis. Both X chromosomes go together to same pole resulting in formation of one gamete with XX and other with no X-chromosome. Fertilization of XX gamete with Y-sperm forms XXY (white eyed female) and fertilization of gamete with no X-chromosome to X-sperm forms red eyed males (X). This phenomenon is known as non-disjunction of two X chromosomes.