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Mitosis
Next Generation: HS.LS1.4 NGSS

Mitosis

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Author: Sophia Tutorial
Description:

This lesson will identify the the function of mitosis and describe why it is an important process in our bodies.

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Tutorial

What's Covered

This lesson will cover the role of Mitosis in the cell cycle by looking at:

  1. The Cell Cycle
  2. Mitosis Phases

1.The Cell Cycle

Mitosis is a part of the cell cycle. The cell cycle describes events that happen from the time a cell is formed until it divides. Mitosis is a type of cell division that happens in somatic cells, all the cells in your body except for sex cells. This process produces new cells. Cells are constantly going through the cell cycle and producing new cells. As cells grow old and die, they need to be replaced by new ones.

Term to Know

    • Cell Cycle
    • Describes the events that occur from the time a cell is formed until it divides.

Interphase is the first part of the cell cycle, but it's not considered to be a part of mitosis. Interphase is the part of the cycle where the cell is getting ready to divide but is not dividing yet. It is the longest phase of the cell cycle, and is where the cell spends most of its life.

Term to Know

    • Interphase
    • A phase of the cell cycle in which a cell carries out its normal functions; includes all parts of a cell’s life except for when the cell is dividing.

There are three sub-phases to interphase:

  • G1- part of interphase is when the cell will start to increase in size and grow in preparation for cell division.
  • S- during this part, DNA is copied and chromosomes are duplicated
  • G2-cell is making its final preparations in order to get ready to divide

Terms to Know

    • G1 Phase
    • The portion of interphase in which a cell grows in size.
    • S Phase
    • The portion of interphase in which a cell’s DNA is copied.
    • G2 Phase
    • The portion of interphase in which a cell makes final preparations for cell division.

Normally in interphase, chromosomes are not visible. Genetic information, or DNA, is found in the form of chromatin, which is like a thread-like ball of yarn that's found within the nucleus. As a cell is preparing to divide, that DNA will then condense into chromosomes which will be copied in preparation for division. Chromosomes are made of sister chromatids attached in the middle at a point called the centromere.

Terms to Know

    • Sister Chromatid
    • A duplicate of an original chromosome produced during mitosis.
    • Centromere
    • The point at which sister chromatids are attached to one another.

mitosis.png


2. Mitosis Phases

Mitosis actually includes four phases:

  • Prophase- the first step in mitosis. During this phase, the nuclear envelope that normally surrounds the genetic information will start to break down. Centrioles, organelles in the cell that play a role in cell division, will start to move towards opposite poles.
  • Metaphase- the second phase of cell division. Chromosomes will line up on the metaphase plate, which is an invisible line in the middle of the cell. Spindle fibers are attached to the centromeres of the chromosomes to prepare these chromosomes to be pulled apart to separate ends of the cell.
  • Anaphase-sister chromatids are separated and moved to opposite ends of the cell.
  • Telophase- the nuclear envelope will begin to reform around the chromosomes, and the plasma membrane will start to pinch off. This area where it's pinching off is called the cleavage furrow.

Term to Know

      • Prophase
      • The first phase of mitosis in which chromosomes are condensed, the nuclear membrane breaks down and centrioles begin to move toward opposite poles.
      • Metaphase
      • The second phase of mitosis in which chromosomes line up on the metaphase plate and are attached at the centromere to spindle fibers.
      • Anaphase
      • The third phase of mitosis in which sister chromatids are separated and pulled by spindle fibers toward opposite poles of the cell.
      • Telophase
      • The final phase of mitosis in which the plasma membrane begins to pinch off and the nuclear membrane begins to reform. Chromosomes begin to return to their thread-like state.
      • Cleavage Furrow
      • The pinching off of the plasma membrane to produce two new cells.

Cytokinesis follows mitosis, and is were two completely new individual cells exist. These two separate cells are diploid daughter cells. They are called diploid because the contain 46 chromosomes, the same number as the parent cell. They are also identical to the parent cell. At this point, the nuclear envelope has completely reformed, and the DNA will return to its thread-like form.

Terms to Know

    • Cytokinesis
    • The end result of mitosis in which two diploid daughter cells are produced which are identical to the parent cell.
    • Diploid
    • Cells that contain two copies of each chromosome.
    • Daughter Cells
    • The name for cells produced by the process of mitosis.

mitosis (2).png

Summary

Mitosis the part of the cell cycle where a cell divides to reproduce. Interphase is the part of the cycle where a cell spends most of its life, and is preparing for mitosis. There are three phases to interphase. G1 is the phase where the cell is growing, S phase is where DNA is copied, and G2 is where the cell makes final preparations for mitosis. During interphase, chromosomes are normally not visible, but as the cell prepares to divide it will condense and become visible. Once duplicated sister chromatid are held together by a centromere. There are four phases of mitosis. Prophase is when the nuclear envelope breaks down and centrioles move to the poles. Metaphase is when the chromosomes start to line up in the middle of the cell and spindle fibers attach to the centromeres of the chromosomes. During Anaphase sister chromatids are separated and move to the poles. Finally, in telophase, the nuclear envelope will begin to reform around the chromosomes and the plasma membrane will pinch off. Cytokinesis follows mitosis, and is where two completely new daughter cells exist.

Keep up the learning and have a great day!

Source: SOURCE: THIS WORK IS ADAPTED FROM SOPHIA AUTHOR AMANDA SODERLIND

Terms to Know
Anaphase

The third phase of mitosis in which sister chromatids are separated and pulled by spindle fibers toward opposite poles of the cell.

Cell Cycle

Describes the events that occur from the time a cell is formed until it divides.

Centromere

The point at which sister chromatids are attached to one another.

Cleavage Furrow

The pinching off of the plasma membrane to produce two new cells.

Cytokinesis

The end result of mitosis in which two diploid daughter cells are produced which are identical to the parent cell.

Daughter Cells

The name for cells produced by the process of mitosis.

Diploid

Cells that contain two copies of each chromosome.

G1 Phase

The portion of interphase in which a cell grows in size.

G2 Phase

The portion of interphase in which a cell makes final preparations for cell division.

Interphase

A phase of the cell cycle in which a cell carries out its normal functions; includes all parts of a cell’s life except for when the cell is dividing.

Metaphase

The second phase of mitosis in which chromosomes line up on the metaphase plate and are attached at the centromere to spindle fibers.

Prophase

The first phase of mitosis in which chromosomes are condensed, the nuclear membrane breaks down and centrioles begin to move toward opposite poles.

S Phase

The portion of interphase in which a cell’s DNA is copied.

Sister Chromatid

A duplicate of an original chromosome produced during mitosis.

Telophase

The final phase of mitosis in which the plasma membrane begins to pinch off and the nuclear membrane begins to reform. Chromosomes begin to return to their thread-like state.