How Cells Reproduce

• Reasons for cell division • Create more cells - Growth - Repair of damage • To create new organisms - Asexual reproduction - Production of gametes (eggs or sperm)

• cloning • Two daughter cells • daughters genetically identical • Growth, repair, or asexual reproduction

• Four daughter cells • Daughters genetically different • Sexual reproduction

2 sets of chromosomes

1 set of chromosomes

a molecule of DNA

DNA molecule

a body cell

only cells that can do meiosis

• Interphase: G1, S, G2 • Mitosis: Prophase, Metaphase, Anaphase, Telophase • Cytokinesis

• Mitosis begins - Duplicated chromosomes begin to condense

• New microtubles are assembled • One centriole pair is moved toward opposite pole of spindle • Nuclear envelope starts to break up

• Spindle forms - Spindle microtubules attach to sister chromatids of each chromosome

• All chromosomes are lined up at the spindle equator - Chromosomes are maximally condensed

• Sister chromatids are pulled apart - Once separated, each chromatid is a chromosome

• Chromosomes decondense - Two nuclear membrans form, one around each set of chromosomes

• Occurs simultaneously with telophase • Divides non-nuclear organelles between cells • Two mechanisms • Cleavage (animals) • Cell plate formation (plants)

• Two daughter nuclei • Each genetically identical to parent cell • Chromosomes in unduplicated form

• Things that regulate the cell cycle • Growth factors • Cell Density • Surface Recognition • Loss of control - Tumors-grows without control • Cancer-spread from where it started (a tumor that spreads)

• Abnormal cells that have lost control over how they grow and divide • Benign-grow slowly, retain surface recognition • Malignant-disrupting surrounding tissues, metastasize

• Growing cells in culture allows researchers to investigate processes and test treatments without danger to patients • Most cells CANNOT be grown in culture

• Line of human cancer cells that can be grown in culture • Descendants of tumor cells from a woman named Henrietta Lacks • Lacks died at 31, but her cells continue to live and divide in labs around the world