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The Cell Cycle — Reading Comprehension

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MS-LS1-4

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This middle school science reading passage introduces the cell cycle as the life of a cell from formation to division. Aligned to NGSS standard MS-LS1-4, it explains the three main stages—interphase, mitosis, and cytokinesis—using accessible language, scientific vocabulary, and real-world examples. Students learn about the mechanisms, importance, and variation in cell cycle length, with connections to health and society. Included are a glossary, multiple-choice and writing activities, and graphic organizers to support comprehension. This resource is suitable for grades 6-8, supports science literacy, and includes audio integration for diverse learners. The passage helps students build foundational understanding of cell biology and prepares them for advanced life science topics.

CONTENT PREVIEW

The cell cycle describes the series of changes a cell undergoes from the moment it forms until it divides to create new cells. This process is vital for growth, repair, and reproduction in all living organisms. Cells in your skin, blood, and organs are constantly going through the cell cycle to keep your body healthy and functioning. Understanding the cell cycle helps scientists learn how diseases like cancer develop when this process goes wrong.

Stages of the Cell Cycle

The cell cycle consists of three main stages: interphase, mitosis, and cytokinesis. Most of a cell’s life is spent in interphase, which includes three phases: G1 (growth), S (DNA synthesis or replication), and G2 (preparation for division). During G1, the cell grows and carries out its normal functions. In the S phase, the cell copies its DNA, ensuring that each new cell will have a complete set of genetic information. During G2, the cell prepares all the components needed for division. Next, mitosis begins. Mitosis is the process by which the cell’s nucleus divides, with the duplicated chromosomes being carefully separated into two identical groups. Finally, cytokinesis divides the cell’s cytoplasm, forming two new daughter cells.

Variation and Importance in the Cell Cycle

The length and timing of the cell cycle can vary widely. For example, some bacteria complete the cell cycle in about 20 minutes, while human skin cells take about 24 hours. Nerve cells in adults may never divide again after maturing. These differences are crucial for the health and efficiency of tissues. If cells divide too quickly or uncontrollably, as in cancer, the organism can be harmed. Scientists use techniques like microscopes and DNA-staining to observe cells at different stages of the cycle, which helps them understand normal development and disease.

Applications and Broader Connections

Knowledge of the cell cycle has real-world applications. Medical researchers study how drugs can target cancer cells by interrupting their cycle. Technological advances in genetics and biotechnology rely on manipulating the cell cycle for cloning or repairing tissues. In agriculture, understanding cell division can improve crop yields. The cell cycle is a central concept in biology, showing how structure and function are connected and how living systems maintain balance.

In summary, the cell cycle is an organized, step-by-step process that allows cells to grow, replicate their DNA, and divide, ensuring the continuation and health of all living things. By studying the cell cycle, scientists can develop new ways to improve medicine, agriculture, and technology.

Interesting Fact: Some cells, like those in your brain, can remain in a resting phase for decades, never dividing again after they mature!

What is the main purpose of the cell cycle?

To allow cells to grow, replicate their DNA, and divideTo make cells rest for long periodsTo help cells move around the bodyTo provide energy for the cell

Which phase does a cell spend most of its life in?

InterphaseMitosisCytokinesisResting phase

What happens during the S phase of interphase?

The cell copies its DNAThe cell divides its cytoplasmThe nucleus disappearsThe chromosomes move to the center

What is mitosis?

The process when the nucleus dividesThe step where the cell growsThe splitting of cytoplasmThe resting phase

What are daughter cells?

The two new cells formed after cell divisionCells that never divideCells that only growCells in the resting phase

Which word in the passage means the process of copying DNA?

DNA replicationInterphaseCytokinesisChromosomes

How do scientists observe different stages of the cell cycle?

By using microscopes and DNA-stainingBy using only their eyesBy listening to cell soundsBy counting the number of cells