CHAPTER 10 Cell Growth and Division: Mitosis Play Video

Background Living things grow by producing more cells. This occurs through a process called mitosis, which is (aesexual) cell division. Cell division (stage 1. mitosis & stage 2. cytokinesis) results in “two identical daughter cells.” Before division occurs, the cell replicates/copies all of its DNA. Then each new cell has its own complete copy of the DNA for each new cell. Mitosis is needed for growth and repair of tissues, and replaces lost cells (skin, digestion).

Chromosomes Chromosomes carry the genetic info that is passed from one generation of cells to the next. Made of DNA The cells of every organism have a specific number of chromosomes; humans have 46 (diploid = 2n). 23 (haploid) come from mom, 23 (haploid = n) from dad. Before the actual division occurs, the DNA doubles itself, so there are 2 identical “sister” chromatids; one sister chromatid goes to each of the two new cells. Each pair of chromatids are attached at the centromere.

Chromosomes Play Video

The Cell Cycle During the cell cycle, a cell grows, prepares for division, and divides to form 2 daughter cells, each of which begins the cycle again. The cell cycle (the cell’s whole life) consists of 4 phases: 1. M-phase (mitosis & cytokinesis) 2. G1- cell growth and activity 3. S-phase (chromosome replication) 4. G2- cell growth and activity, prep for mitosis * G = gap Interphase

Mitosis There are 4 phases of mitosis: 1. Prophase 2. Metaphase 3. Anaphase 4. Telophase Depending on the type of cell, mitosis can last a few minutes to several days. Play Video DNA replication Mitosis Two diploid cells

Prophase Chromatin condenses into chromosomes Centrioles separate Spindles begin to form Nuclear envelope breaks down Chromosomal material most visible

Metaphase Chromosomes line up across the center of the cell (equitorial plate) Each chromosome is connected to a spindle fiber at its centromere

Anaphase The sister chromatids separate into individual chromosomes and are moved apart.

Telophase Chromosomes gather up at opposite ends of the cell and lose their distinct shapes. Two new nuclear envelopes form.

Cytokinesis The cytoplasm pinches in half (animal cells) OR A cell plate forms halfway between the two nuclei- new cell wall (plant cells) Either way, each daughter cell has an identical set of duplicate chromosomes telophase Cell plate

Regulating Cell Growth Cells grow and divide depending on the cell type. Cyclin regulates the timing of the cell cycle in eukaryotic cells. Other internal and external regulators control timing, etc. Cancer: cells that do not respond to the signals that regulate the growth of most cells. Cancer cells grow uncontrollably and create masses called tumors.

Mitosis Lab Low powerMedium power High power Also called alium root tip. The tip of the root is a place where a lot of mitosis takes place; as the root grows through the soil, mitosis replaces lost cells and adds cells to lengthen the root.