The biconcave shape of erythrocytes is a result of

The answer would be: peripheral proteins anchored to the inner surface of their plasma membrane

Red blood cells have ankyrin and spectrin protein in their membrane that responsible for their biconcave shape. The shape itself is beneficial because it allows a larger surface area to accommodate gas exchange. It also allows the red blood cells to be squeezed into the narrow capillary blood vessels.

Since a female is both xx chromosome and the male passes down the x chromosome, than the offspring would be female since a female is xx.