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 same number of chromosomes.

Cytokinesis

• Cytokinesis is the division of the cytoplasm.

Asexual Reproduction

• Asexual reproduction involves only one parent.
• Therefore, specialized reproductive organs are not needed.
• It occurs through mitosis.
• Each offspring has the same genetic information as the parent.

Chromatin and Chromosomes

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

Interphase

• Interphase is known as the "resting" phase.
• During Interphase:
  • Cells grow in size by producing more nucleic acids and proteins.
  • Cellular organelles make copies of themselves.
  • Chromosomes make copies of themselves, but are not visible.
  • Centrioles are present and duplicate.

Prophase

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

Metaphase

• Centromeres line up on the equator (middle = metaphase plate) of the cell.
• By the end of metaphase, centromeres divide and pull the daughter chromosomes to opposite sides of the cell.

Anaphase

• Daughter chromosomes move to opposite sides of the cell (poles).
• Movement is accomplished by shortening of the microtubules.

Telophase

• Chromosomes uncoil and return to their threadlike shape.
• Nuclear membrane and nuclei reform.
• Cytokinesis begins in late anaphase and finishes during telophase.

Mitosis in Plants

• Similar to animal mitosis, but plants lack centrioles.
• Spindle fibers take their place.
• A cell plate divides the plant cell instead of pinching, due to the rigid cell wall.

Asexual Reproduction Types

• There are five different types of asexual reproduction.

  1. Budding: Parent divides unequally, creating new individuals from buds. Examples include yeast and hydra.
  2. Binary Fission: Parent divides equally, forming two separate individuals. An example is paramecium.
  3. Spore Formation: Single specialized cells (spores) released from the parent germinate and grow. Spores are usually coated for protection, and are common in many plants and fungi.
  4. Regeneration/Fragmentation: Ability of an organism to regrow body parts from a fragment or part of the body. Examples include hydra and starfish.
  5. Vegetative Reproduction/Propagation: Roots, stems, and leaves divide and differentiate, creating the same organism. Examples include strawberry plants and pick-a-back plants.

Protein

• Cyclin is a protein that causes cells to go through the cell cycle.

Mnemonic Device

• A helpful memory tool for the phases of mitosis is: I PUNCHED MY AUNT TILLY!

This quiz covers the key concepts of the cell cycle, including mitosis, cytokinesis, and asexual reproduction. Understand how unicellular and multicellular organisms utilize cell division and learn about chromatin and chromosomes. Test your knowledge on the phases of mitosis and the interphase.