CELL CYCLE NOTES I Growth and Development Complex

CELL CYCLE NOTES

I. Growth and Development • Complex organisms begin life as a single, microscopic cell called a zygote (fertilized egg). * So how do they become large, multicellular organisms……

• Organisms grow by increasing number of cells through the process of cell division. o Ex: 1 2 4 8 16 32 64

• As organisms grow, cells differentiate (their structure changes). o Cells specialize to perform specific jobs or functions (skin cells, muscle cells, nerve cells).

II. Cell Cycle A. Cell cycle has three stages: Interphase, Mitosis and Cytokinesis

1. Interphase: period of growth & development. • DNA called chromatin during interphase. Chromatin = long thin strands of DNA. • DNA called chromosomes during mitosis. Chromosomes = coiled up chains of DNA.

Chromatin Chromosomes

2. Mitosis: cell division OR equal division of the nucleus • Form of asexual reproduction (cell makes copy of hereditary material identical to parent). • Creates 2 identical copies of the original cell. • Has 4 stages: prophase, metaphase, anaphase and telophase.

A. Mitosis in Humans • Starts with one cell (parent cell) that has 23 chromosome pairs, or 46 chromosomes total. • Ends with two cells (daughter cells); each cell has 23 chromosome pairs, or 46 chromosomes.

• Blood and skin cells go through mitosis frequently for replacement. • Muscle and nerve cells remain in interphase 3. Cytokinesis: equal division of the cytoplasm. Results in 2 new daughter cells

Cell Cycle cell grows and carries out normal activities; organelles duplicate DNA replicates cell grows and prepares for mitosis

B. To remember the order think: • I PMAT C (interphase prophase, metaphase, anaphase, telophase cytokinesis)

Interphase Chromosome Cytokinesis Telophase Prophase Metaphase Centriole Centromere Spindle Fiber Anaphase

Click on the link below and enter the web code to do an interactive activity on mitosis • http: //www. phschool. com/ – web code: cep - 3023