Cell Division Cell Division When a parent cell

Cell Division

Cell Division When a parent cell divides, producing 2 or more daughter cells.

Reasons cells divide 1. Reproduction (unicellular)

2. Growth & development

3. Maintenance (old, injured, or large cells)

Cell Size § Almost every cell on earth is roughly the same size. Just like all living things, cells need oxygen and nutrients to thrive.

The cell uses its cell membrane to get these things. A large cell may not get what it needs fast enough to survive. Once it reaches a certain size, the cell will divide or die!

How Information is passed on… § instructions for traits are found on genes. § Genes are found on chromosomes Gene

§ Chromosomes are x-shaped structures in the nucleus that are made of DNA § DNA = instruction manual for life!!!

Looks like this only during cell division

Human Cell Types § Somatic Cells – all body cells (except sperm/egg) § 46 chromosomes § Gametes – sperm/egg; half the # of chromosomes § 23 chromosomes

The Cell Cycle 1. Cell grows 2. Prepares for division 3. Divides into 2 identical cells; called daughter cells 4. Each cell begins cycle

Mitosis § Cell division producing identical cells are produced. § 4 stages

§ Mitosis makes new cells needed for an organism’s growth. § These cells differentiate into specific cells with special functions, depending on their location.

§ Mutations are changes in the original DNA or chromosome. § Mutations that occur during Mitosis do not get passed on to your offspring.

Regulation of Cell Cycle § Cyclins tell cells when to divide & stop § Some divide frequently (skin) § Others rarely (nerve, muscle)

Cancer § Cancer cell do not respond to “stop” signals § Uncontrolled cell growth = tumor § Tumors and cancer cells disrupt normal activities needed to survive