Question

why red blood cells have no nucleus

Answer 1

because It allows the red blood cell to containmore haemoglobin (and, therefore, carry more oxygen molecules). It also allows the cell to have its distinctive bi-concave shape which aids diffusion - this shape would not be possible if the cell had a nucleus in the way.

Answer 2

it's only the RBC's which doesn't have nuclear , however they have the nucleus when they start of their journey from the spleen . The reason for it's absence is because, it allows the red blood cell to contain more haemoglobin (and, therefore, carry more oxygen molecules). It also allows the cell to have its distinctive bi-concave shape which aids diffusion - this shape would not be possible if the cell had a nucleus in the way.