21.1.3Explain how instructions in DNA lead to cell differentiation and result in cells specialized to perform specific functions in multicellular organisms.
3Specialized CellsMulticellular organisms begin as undifferentiated masses of cells and variation in DNA expression and gene activity determines the differentiation of cells and ultimately their specialization.
4DifferentiationOnly specific parts of the DNA are activated; the parts of the DNA that are activated determine the function and specialized structure of a cell.Because all cells contain the same DNA, all cells initially have the potential to become any type of cell; however; once a cell differentiates, the process cannot be reversed.
5DNANearly all the cells in an organism contain the same chromosomes and DNA.Different parts of the genetic instructions are used in different types of cells, influenced by the cell’s environment and past history.
6HormonesHormones are chemical signals that are released by cells that influence the development and activity of other cells.
7Stem CellsUnspecialized cells that continually reproduce themselves and have, under appropriate conditions, the ability to differentiate into one or more types of specialized cells.
8Types of Stem Cells Embryonic stem cells Adult stem cells- found in bone marrowResearch has demonstrated both types of stem cells can be differentiated into specialized cells.
9Specialized cells in Animals Nerve cells- eukaryotic, but have dendrites and axons for electrochemical communication in the body.They are never replaced when they die.
10Specialized cells in Animals Muscle cells- eukaryotic; used for movement.Skeletal muscles contain many nuclei and are striated- voluntary movement.Smooth muscles only have 1 nucleus- involuntary movement
11Specialized cells in Animals Blood cellsRed blood cells- the hemoglobin protein transports oxygen and carbon dioxide (influenced by temperature and pH)Do not divideNo mitochondria or nucleusPlasma- transports materialsInsulin regulates glucose levelsLipids, amino acids, and other ions also transported from digestive system.White blood cells- protects the body from infectionHas a nucleus