Question

A cross between white eyed female and red eyed male Drosophila gives rise red eyed females and white eyed male. Rarely this cross gives rise to white eyed females and red eyed males. This is due to

• A. Loss of one X chromosome
• B. Segregation of X chromosome in female
• C. Non-disjunction of X chromosome in female
• D. Non-disjunction of X chromosome in male

Answer 1

The correct option is C Non-disjunction of X chromosome in female

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-seperation of two homologous X chromosomes during anaphase I of meiosis. Both X chromosomes go together to same pole resulting in formation of one XXY (white eyes female) and red eyed males. This phenomenon is known as non disjunction of two X chromosomes. Hence, option C is correct.