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Cell Division: Mitosis — Reading Comprehension

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MS-LS1-4

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This comprehensive science passage for middle school students explores the key concept of mitosis, the division of the nucleus into two identical daughter cells. Aligned with NGSS standard MS-LS1-4, the passage explains the mechanisms of mitosis, details the four phases (Prophase, Metaphase, Anaphase, Telophase) using the PMAT mnemonic, and connects the process to real-world applications such as growth, tissue repair, and asexual reproduction. Students will discover how mitosis supports multicellular life and examine both the systems and interactions involved. The resource includes a glossary, differentiated versions, a Spanish translation, diagrams, quizzes, writing prompts, and graphic organizers, making it ideal for diverse learners. Audio integration supports accessibility. This resource is perfect for grades 6-8 science instruction, providing a blend of scientific explanation, examples, and critical thinking activities.

CONTENT PREVIEW

Mitosis is the essential process by which a eukaryotic cell divides its nucleus to create two identical nuclei. This mechanism ensures that each new cell receives the exact same genetic material as the original. Without mitosis, multicellular organisms could not grow, heal, or replace damaged cells. The process of mitosis is especially important for tissue growth in animals, leaf formation in plants, and even some forms of asexual reproduction.

The Mechanism of Mitosis: How Does It Work?

During mitosis, a single cell undergoes a series of well-organized steps to evenly split its chromosomes. These steps are grouped into four main phases, often remembered by the mnemonic PMAT: Prophase, Metaphase, Anaphase, and Telophase. In Prophase, the chromosomes condense and become visible under a microscope, and the nuclear membrane breaks down. Next, during Metaphase, the chromosomes align at the cell’s center. In Anaphase, the chromosomes are pulled apart to opposite poles of the cell. Finally, in Telophase, new nuclear membranes form around each set of chromosomes, creating two distinct nuclei. The result is two genetically identical daughter cells, each with the same number of chromosomes as the parent cell.

Applications and Interactions: Why Is Mitosis Important?

Mitosis plays a crucial role in the life of all multicellular organisms. For example, when a human child grows from 50 centimeters to 160 centimeters, trillions of cells must divide through mitosis. After an injury, such as a scraped knee, mitosis allows skin cells to multiply and repair the wound. In plants, mitosis enables roots and shoots to extend for better nutrient absorption and light capture. Some organisms, like single-celled amoebas or hydra, reproduce asexually by mitosis, creating offspring that are clones of the parent. The accuracy of mitosis is vital: if chromosomes are not evenly divided, it can result in genetic disorders or cell malfunction.

Complexities and Broader Implications

Mitosis does not act alone; it is part of the larger cell cycle that also includes periods of growth and DNA replication. Scientists first identified mitosis in the late 19th century using improved microscopes and staining techniques, which allowed them to observe chromosome movement. Errors in mitosis can lead to diseases like cancer, where cells divide uncontrollably. Advances in cell biology now allow researchers to study mitosis in real time, leading to treatments that can target dividing cancer cells while sparing healthy ones.

Understanding mitosis deepens our knowledge of how living systems grow, heal, and reproduce. This process connects to larger scientific principles of heredity, stability, and change. By studying mitosis, scientists can uncover causes of disease, improve agriculture, and design new medical therapies.

Interesting Fact: Every second, your body completes about two trillion mitotic cell divisions to keep you alive and healthy!

What is the main purpose of mitosis in multicellular organisms?

To help organisms grow, repair, and replace cellsTo break down food moleculesTo allow breathingTo make energy from sunlight

Which phase of mitosis involves chromosomes lining up at the cell's center?

ProphaseMetaphaseAnaphaseTelophase

What is the result of mitosis?

Two genetically identical daughter cellsFour different cellsCells with half the number of chromosomesCells that are larger than the original

What does the 'PMAT' mnemonic help students remember?

The four phases of mitosisThe types of cells in the bodyThe steps in photosynthesisThe organs in a plant

What happens during Anaphase?

Chromosomes separate and move to opposite polesChromosomes condense and nuclear membrane breaks downChromosomes align at the cell's centerNew nuclear membranes form

What does 'genetically identical' mean in the passage?

Having the same DNA as the original cellBeing completely differentHaving more chromosomesHaving half the genes

Why is accuracy in mitosis important?

Mistakes can cause genetic disorders or malfunctionCells could become smallerOrganisms would stop breathingPlants would stop growing

How do scientists study mitosis today?

By observing cells in real time with advanced toolsBy only guessingBy heating cellsBy using plant roots only

Mitosis creates cells that are genetically identical to the parent cell. (True/False)

TrueFalse

Errors in mitosis can result in cancer. (True/False)

TrueFalse