Question

what is an example of gene expression regarding human development?
bone marrow starting to make adult hemoglobin after birth
eye color stays the same after birth
brain cells stop developing over time
muscle cells grow smaller during exercise

Explanation:

Gene expression refers to the process where genes are activated to produce functional products like proteins. After birth, human bodies switch from producing fetal hemoglobin (adapted for oxygen transfer in the womb) to adult hemoglobin; this is a direct result of specific genes being turned on/off in bone marrow cells, which is a clear example of gene expression during human development. The other options do not involve changes in gene activity: eye color stability is a fixed trait, brain cell development cessation is a structural change not tied to gene expression, and muscle cell size change during exercise is a physiological adaptation from use, not gene expression.

Answer:

A. Bone marrow starting to make adult hemoglobin after birth