Which of the following best describes how a wide variety of specialized cells can originate from the same undifferentiated mass of cells?

A. After fertilization and cellular division, each cell contains different DNA which forms a different type of specialized cell.

B. Cells can change from one specialization to another depending on the needs of the organism.

C. Each type of specialized cell is contained within the sex cells before fertilization occurs.

D. All cells contain the same DNA, but only specific parts of the DNA are activated to determine a cells specialization.

All the cells in a human body contains same DNA which contains all the genes required for human body to live. But different parts of DNA are activated in different cells which marks the specialization of different cells.

Option D

Explanation:

A human body is formed by repeated division of a single cell which is the zygote. The zygote contains all the chromosomes and all the DNAs. Now the zygote undergoes cleavage divisions to form the multicellular morula and then blastula and ultimately blastocyst. This blastocyst then undergoes a change in structure to form three layers called the embryonic ectoderm, mesoderm and endoderm. Now different cells from these layers undergo physical changes to form different tissues like neural tissue, muscular tissue, blood and everything.

This is possible because in different cells, different regions of DNA gets activated to form mRNAs and proteins to prepare them into different tissues. This is called Differentiation.