5.1 Cell Differentiation

• What is cell differentiation?

  Changes in physical and functional properties of cells
• Why is cell differentiation important in embryonic development?

  It forms different bodily structures and organs
• What happens when the nucleus from an intestinal mucosal cell is implanted into a frog ovum?

  It often results in the formation of a normal frog
• What does the frog nucleus experiment demonstrate about differentiated cells?

  Differentiated cells carry all necessary genetic information
• How does differentiation occur according to the study material?

  Through selective repression of different gene promoters
• What do electron micrographs suggest about DNA during differentiation?

  Some DNA segments become condensed and inactive
• What is proposed about the cellular genome during differentiation?

  It produces a regulatory protein that represses genes
• How many proteins do mature human cells typically produce?

  About 8000 to 10,000 proteins
• What role do certain cells in an embryo play in differentiation?

  They control differentiation of adjacent cells
• What is the primary organizer of the embryo?

  The primordial chorda-mesoderm
• What does the primordial chorda-mesoderm differentiate into?

  A mesodermal axis with segmentally arranged somites
• How does the developing eye vesicle affect the ectoderm?

  It causes the ectoderm to thicken into a lens plate
• What is the significance of induction in embryonic development?

  It allows one part of the body to affect another
• What is the current understanding of cell differentiation mechanisms?

  Many control mechanisms are known, but still unclear