Cell Cycle and Mitosis Overview

Cell Cycle

• The cell cycle is the period of time between one cell division and the next
• In unicellular organisms, cell division creates new individuals
• In multicellular organisms, cell division replaces old or damaged cells

Mitosis

• Mitosis is the process where the nucleus divides, maintaining the number of chromosomes
• A critical process for cell growth and development

Cytokinesis

• Cytokinesis is the division of the cytoplasm
• It occurs after mitosis

Asexual Reproduction

• Asexual reproduction involves only one parent
• It does not require special reproductive organs
• Offspring have the same genetic information as the parent

Chromatin and Chromosomes

• Chromatin is DNA wound around proteins called histones
• Chromosomes are condensed chromatin, easily visible during mitosis (rod-like structures)
• Mitosis has 5 phases

Interphase

• Interphase is known as the "resting phase"
• Cells grow in size by producing more nucleic acids and proteins
• Cellular organelles are copied
• Chromosomes copy themselves (though not visible under the microscope)

Prophase

• Double chromosomes become visible
• Chromosomes are made of two sister chromatids connected by a centromere

Metaphase

• During metaphase, centromeres line up along the equator (metaphase plate)
• The centromeres divide
• Daughter chromosomes are pulled to opposite sides of the cell
• Each chromosome divides equally

Anaphase

• Daughter chromosomes move to opposite poles of the cell
• Movement is achieved by shortening microtubules

Telophase

• Chromosomes uncoil, returning to their threadlike shape
• Nuclear membrane and nuclei reform
• Cytokinesis, which began in late anaphase, is complete during telophase

Mitosis in Plants

• Plant mitosis is similar to animal mitosis, except plants lack centrioles
• Spindle fibers still direct the movement of chromosomes
• Cell walls prevent the pinching process, resulting instead in the development of a cell plate to separate the two new cells

Asexual Reproduction Types

• There are 5 types of asexual reproduction
  • Budding: Parent divides unequally, creating buds that form new individuals (ex., yeast and hydra)
  • Binary fission: Parent divides equally into two new individuals (ex., paramecium)
  • Spore formation: Specialized cells germinate when released from the parent (usually with a protective coating)
  • Regeneration/Fragmentation: Ability to regrow body parts or reproduce from newly separated fragments (ex., hydra, planaria, starfish)
  • Vegetative propagation: Roots, stems, and leaves enable the growth of new plants (ex., strawberries, pick-a-back plants)

Mnemonic Device

• "I PUNCHED MY AUNT TILLY" is a memory aid for remembering the order of the phases of mitosis

Protein that causes cells to go through cell cycle

• Protein that causes cell cycles is called cyclin