Mitosis Cell Division Cell Grows INTERPHASE Genetic Material

Mitosis & Cell Division

-Cell Grows INTERPHASE -Genetic Material Replicates -Errors are corrected

Mitosis n. A continuous process that is divided into four stages: -Prohphase -Metaphase -Anaphase -Telophase

Prophase n 1. Nuclear envelope begins to break down n 2. Chromosomes condense and become visible n 3. Microtubules form around nucleus creating mitotic spindle n 4. Centrioles segregate to opposite ends of the cell n 5. Towards the end of this phase, the microtubules attach to the kinetechore (part of the centromere) of the chromatids

Prophase in Onion Root Tip Prophase

Metaphase n Sister chromatids begin to line up towards the middle of the cell forming the metephase plate § The metephase plate lines up perpendicular to the spindles such that each new nuclei ends up with one copy of each chromosome

Metaphase in Onion Root Tip Metaphase

Anaphase n Beginning of chromosome segregation – Proteins break down centromeres – Motor proteins begin to move chromosomes along the microtubules towards the opposite ends of the cell n If there are errors during this stage, the chromosomes do not separate equally, causing aneuploid cells. – One nucleus has a greater number of chromosomes than the other. Q: Why do you think this may be harmful to the organism?

Anaphase in Onion Root Tip Anaphase

Telophase n Chromosomes begin to expand are no longer visible n The nuclear envelope begins to reform, creating two nuclei Telophase in Onion Root Tip

Cytokinesis n n n The plasma membrane begins to constrict between the two newly formed nuclei The cell is divided into two In plants, cell plate is formed as vesicles containing cell membrane materials fuse together along the equator of the cell. – Once cells are divided, cellulose is secreted to form cell wall. n The new cells now enter G 1

Cytokinesis in Plant Cell Cytokinesis in Animal Cell

References n n n http: //www. biology. arizona. edu/cell_bio/tutorials/cell_cy cle/cells 3. html http: //www. botany. org/plantimages/Mitosis. php BSCS Biology: A Molecular Approach (8 th ed. ). (2001). Columbus, OH: Glencoe/Mc. Graw-Hill Cooper, G. M. (2000). The Cell: A Molecular Approach (2 nd ed). Washington, DC: ASM Press http: //faculty. clintoncc. suny. edu/faculty/Michael. Gregory /files/Bio%20101%20 Lectures/Mitosis/mitosi s. htm