Question

which statement about cellular differentiation is correct?
cells begin to differentiate immediately after fertilization at the two - cell stage.
even after cells have differentiated, they still produce all of the proteins needed for every tissue type.
cells in a human embryo do not begin to differentiate until the zygote has undergone several divisions.
once cells have differentiated, the dna not needed by the cell is removed by special enzymes.

Explanation:

Cellular differentiation is a process where cells become specialized. In humans, cells in an embryo do not start differentiating until after several cell divisions. Differentiated cells still retain all the DNA needed to produce proteins for various tissue types (DNA is not removed as in option 1). Differentiation doesn't start immediately after fertilization (contradicts option 4).

Answer:

Cells in a human embryo do not begin to differentiate until the zygote has undergone several divisions.