Mitosis in Animal and Plant Cells

Once students understand the basic structure of DNA and chromosomes, they focus on the phenomena of how cells grow and then divide in mitosis to produce new daughter cells. Those new cells contain DNA from the parent cell. Cell division allows for growth, repair, and reproduction.

• Cells grow, develop, and pass along their genetic information in a process called a life cycle. Scientists who are interested in cells often study a cell’s life cycle.
• One step in the cell cycle is called mitosis.Mitosis is an essential part of the cell life cycle.
• Mitosis is cell division that results in two daughter cells with the same number and kind of chromosomes as the parent cell. Mitosis results in new, genetically identical cells.
• Many of the cells in multicellular organisms such as plants and animals undergo mitosis frequently for growth and healing.
• Cells are constantly changing as they go through mitosis. The ability to grow, develop, and heal means that cells cannot remain static and unchanging.

• Why do cells have a cell cycle?
• Why do cells spend most of their lives in interphase?
• Why is it important that cells replicate their DNA during interphase?
• What are some of the reasons that cells divide?
• How can we tell when a cell is beginning mitosis?
• Why do cells in mitosis spend more time in prophase than any other phase?
• Why is it important that the chromosome pairs line up in the middle of the cell end to end?
• How can we tell that anaphase is beginning?
• Why do cells in plants and animals undergo mitosis so frequently?
• How does mitosis provide evidence that cells are dynamic and always changing?

Misconception: Organisms grow because cells get bigger.

Fact: Organisms grow because cells divide. 

Misconception: Cell division results in a decrease in the number of chromosomes.

Fact: In mitosis, cells divide to create exact replicas of themselves, with the same number and kind of chromosome. In meiosis, the daughter cells have half the number of chromosomes as the parent cell.

Cell cycle : an ordered series of events that ends in cell division; consists of interphase and mitosis

Cell division : the splitting of a single cell into daughter cells, each with DNA from its parent cell

Daughter cell : a cell formed by the division of a parent cell

Interphase : the part of the cell cycle when a cell performs its normal functions

Life cycle : the series of developmental stages an organism passes through on its way from birth to death

Mitosis : a form of cell division that results in two daughter cells with the same number of chromosomes as the parent cell

Replicate : to make a copy

The Bristlecone Pine

There is a tree in the White Mountains of California that scientists believe is more than 5,000 years old. This tree, a bristlecone pine, is the oldest known individual tree in the world.

Scientists who are interested in the long lifespan of the bristlecone pine have compared seeds and pollen from bristlecone pines of different ages. They found that the cells of the old trees appeared just as young as the cells of the younger trees.

No one really understands how the bristlecone pine can live so long. This is something scientists are continuing to study. But scientists know it has something to do with the life cycle of the tree’s cells. A life cycle is the series of developmental stages an organism passes through on its way from birth to death. The lifespan of a cell ranges from 1 day to more than 100 years.

All cells follow a similar pattern of development. All cells first grow, and then they divide to produce new daughter cells, which are cells formed by the division of a parent cell. Those daughter cells contain DNA from the parent cell. This ordered series of events, which moves from growth to division, is called the cell cycle.

The Growing Phase

A typical animal cell cycle lasts roughly 24 hours, although in some animal cells it lasts less than 8 hours, while in other kinds of cells it takes more than a year. The majority of the cell cycle is spent in interphase—the period of the time when a cell performs its normal functions. For example, a human muscle cell contracts and relaxes during interphase, enabling you to move.

New nucleotides are added to each unzipped strand of the DNA molecule: adenine (A) pairs with thymine (T) and guanine (G) pairs with cytosine (C). The two new strands are both exact replicas of the original DNA molecule. The two identical chromosomes that result from DNA replication are referred to as sister chromatids. They are linked together by the centromere. The chromosomes are not visible during interphase.

Interphase is also when the cell grows, nearly doubling its size. Finally, DNA is replicated during interphase. To replicate means to make a copy of. DNA’s structure allows it to replicate because each strand of the double helix runs in opposite directions. Before a cell divides, the twisted, tightly packed double helix unwinds and separates its two strands, unzipping down the the cell cycle middle. Each strand serves as a template for a new strand of DNA.

The Growing Phase

A typical animal cell cycle lasts roughly 24 hours, although in some animal cells it lasts less than 8 hours, while in other kinds of cells it takes more than a year. The majority of the cell cycle is spent in interphase—the period of the time when a cell performs its normal functions. For example, a human muscle cell contracts and relaxes during interphase, enabling you to move.

New nucleotides are added to each unzipped strand of the DNA molecule: adenine (A) pairs with thymine (T) and guanine (G) pairs with cytosine (C). The two new strands are both exact replicas of the original DNA molecule. The two identical chromosomes that result from DNA replication are referred to as sister chromatids. They are linked together by the centromere. The chromosomes are not visible during interphase.

Interphase is also when the cell grows, nearly doubling its size. Finally, DNA is replicated during interphase. To replicate means to make a copy of. DNA’s structure allows it to replicate because each strand of the double helix runs in opposite directions. Before a cell divides, the twisted, tightly packed double helix unwinds and separates its two strands, unzipping down the the cell cycle middle. Each strand serves as a template for a new strand of DNA.

In this lesson, students use microscopes to explore the phenomena of mitosis. They identify and diagram the stages of mitosis in animal and plant cells. Students gather and analyze data from this investigation to explore the different stages of mitosis.