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Unit: Developmental biology

How does your body end up with a wide array of cell types, from the smell receptors in your nose to the detoxifying cells in your liver? Learn how cells become more and more specialized over development, taking on the patterns of gene activity that give them their "fate."
Ever seen a fly with legs growing out of its head? How about two newts joined at the belly? If not, read (and watch) on! In this section, we'll explore how molecular signals and transcription factors play key roles in guiding the development of multicellular organisms, and how alterations in these signals can produce starting results.
Did you know that your hands and feet started out like paddles? Your fingers and toes are the result of apoptosis, or the orderly, programmed death of cells. Learn more about apoptosis and how it is important in development (and in the adult body).

About this unit

Did you know that a frog starts out as a single cell? In fact, so do dogs, elephants, and even human beings! Learn how multicellular organisms end up with many different cell types, organized into the tissues and organs of the body.