Cell Differentiation Ms. Cuthrell

1.1.3 Explain how instructions in DNA lead to cell differentiation and result in cells specialized to perform specific functions in multicellular organisms.

Specialized Cells Multicellular organisms begin as undifferentiated masses of cells and variation in DNA expression and gene activity determines the differentiation of cells and ultimately their specialization.

Differentiation Only 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.

DNA Nearly 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.

Hormones Hormones are chemical signals that are released by cells that influence the development and activity of other cells.

Stem Cells Unspecialized cells that continually reproduce themselves and have, under appropriate conditions, the ability to differentiate into one or more types of specialized cells.

Types of Stem Cells Embryonic stem cells Adult stem cells- found in bone marrow Research has demonstrated both types of stem cells can be differentiated into specialized cells.

Specialized cells in Animals Nerve cells- eukaryotic, but have dendrites and axons for electrochemical communication in the body. They are never replaced when they die.

Specialized 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

Specialized cells in Animals Blood cells Red blood cells- the hemoglobin protein transports oxygen and carbon dioxide (influenced by temperature and pH) Do not divide No mitochondria or nucleus Plasma- transports materials Insulin regulates glucose levels Lipids, amino acids, and other ions also transported from digestive system. White blood cells- protects the body from infection Has a nucleus

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Specialized cells in Animals Gametes- Sperm and egg cell Used in sexual reproduction Only contain half the DNA as the rest of the cells in an organisms. Haploid number for humans= 23 chromosomes

Specialized Cells in Plants Xylem- transports water from roots Phloem- transports water and sugars

References http://www.sciencedaily.com/releases/2007/12/071220123837.htm heal-thyself.us http://faculty.washington.edu/chudler/cells.html http://www.kidsbiology.com/human_biology/muscles2.php health-niche.com http://www.mcatzone.com/glosslet.php?letter=g ap-bio-patrick-steed.wikispaces.com