The cell cycle: interphase, mitosis, cytokinesis

Interphase Is divided into 3 parts: Is divided into 3 parts: 1.Rapid growth 2.DNA synthesis and replication 3.Centrioles replicate: cell prepares for division

Interphase Part 1: rapid growth The cell grows The cell grows Protein production is high Protein production is high

Interphase Part 2: DNA synthesis and replication The cell copies its chromosomes The cell copies its chromosomes DNA synthesis does not occur all through interphase but is confined to this specific time DNA synthesis does not occur all through interphase but is confined to this specific time

Interphase part 3: Centrioles replicate: cell prepares for division Centrioles replicate Centrioles replicate Mitochondria and other organelles are manufactured and cell parts needed for cell division are assembled Mitochondria and other organelles are manufactured and cell parts needed for cell division are assembled

As interphase ends… Mitosis begins!

MITOSIS Mitosis is the period of nuclear cell division in which two daughter cells are formed, each containing a complete set of chromosomes Mitosis is the period of nuclear cell division in which two daughter cells are formed, each containing a complete set of chromosomes Cells undergo mitosis (divides) as they approach the maximum cell size at which the nucleus can provide blueprints for proteins and the plasma membrane can efficiently transport nutrients and wastes into and out of the cell. Cells undergo mitosis (divides) as they approach the maximum cell size at which the nucleus can provide blueprints for proteins and the plasma membrane can efficiently transport nutrients and wastes into and out of the cell.

Stages of Mitosis It has 4 stages: It has 4 stages: –Prophase –Metaphase –Anaphase –telophase

Prophase: the first stage This is the first and longest phase of mitosis. This is the first and longest phase of mitosis. The long stringy chromatin coils up into visible chromosomes. The long stringy chromatin coils up into visible chromosomes. Each duplicated chromosome is made up of 2 halves. The two halves of the doubled structure are called SISTER CHROMATIDS. Each duplicated chromosome is made up of 2 halves. The two halves of the doubled structure are called SISTER CHROMATIDS.

The DNA of sister chromatids are exact copies of each other and are formed when DNA is copied during interphase. The DNA of sister chromatids are exact copies of each other and are formed when DNA is copied during interphase.

Prophase continued: Sister chromatids are held together by a structure called a centromere. Sister chromatids are held together by a structure called a centromere. The centromere palys a role in chromosome movement during mitosis The centromere palys a role in chromosome movement during mitosis

Prophase continued: As prophase continues, the nucleus begins to disappear as the nuclear envelope disintegrates. As prophase continues, the nucleus begins to disappear as the nuclear envelope disintegrates. The centrioles begin to migrate to opposite ends of the cell The centrioles begin to migrate to opposite ends of the cell Centrioles are made up of microtubules and are located just outside of the nucleus. Centrioles are made up of microtubules and are located just outside of the nucleus.

Prophase continued As the pairs of centrioles move to opposite ends of the cell the spindle begins to form between them. As the pairs of centrioles move to opposite ends of the cell the spindle begins to form between them. The spindle is a football-shaped cagelike structure made of thin fibers of microtubules. The spindle is a football-shaped cagelike structure made of thin fibers of microtubules. Spindle fibers play a vital role in the separation of sister chromatids. Spindle fibers play a vital role in the separation of sister chromatids.

Metaphase: the second stage of mitosis The doubled chromosomes become attached to the spindle fibers by their centromeres. The doubled chromosomes become attached to the spindle fibers by their centromeres. The chromosomes are pulled by the spindle fibers and begin to line up on the midline, or equator, of the spindle. The chromosomes are pulled by the spindle fibers and begin to line up on the midline, or equator, of the spindle.

Metaphase continued Each sister chromatid is attached to its own spindle fiber. Each sister chromatid is attached to its own spindle fiber. One sister chromatid’s spindle fiber extends to one pole, and the other extends to the opposite pole. One sister chromatid’s spindle fiber extends to one pole, and the other extends to the opposite pole. This arrangement is important because it ensures that each new cell receives an identical and complete set of chromosomes This arrangement is important because it ensures that each new cell receives an identical and complete set of chromosomes

Anaphase: the third stage of mitosis Sister chromatids begin to separate. Sister chromatids begin to separate. The centromers split apart and chromatid pairs separate from each other. The centromers split apart and chromatid pairs separate from each other. The chromatids are pulled apart by the shortening of the microtubules in the spindle fibers. The chromatids are pulled apart by the shortening of the microtubules in the spindle fibers.

Telophase: the fourth & final phase of mitosis Telophase begins as the chromatids reach the opposite poles of the cell. Telophase begins as the chromatids reach the opposite poles of the cell. The chromosomes unwind so they can begin to direct the metabolic activities of the new cells. The chromosomes unwind so they can begin to direct the metabolic activities of the new cells. The spindle begins to break down. The spindle begins to break down. The nuclear envelope begins to reappear The nuclear envelope begins to reappear A new double membrane begins to form between the two new nuclei. A new double membrane begins to form between the two new nuclei.

The end of Mitosis… The beginning of cytokinesis. Cytokinesis – the division of the cells cytoplasm Cytokinesis – the division of the cells cytoplasm Cytokinesis is different in animals and plants Cytokinesis is different in animals and plants Cytokinesis in animals: Cytokinesis in animals: –The plasma membrane pinches in along the equator and the two cells are seperated.

Cytokinesis in Plants: Cytokinesis in Plants: –Plant cells have a rigid cell wall so the plasma membrane does not pinch in. –A structure called the cell plate is laid down across the cell’s equator. –A cell membrane forms around each cell and new cell walls form on each side of the cell plate until separation is complete.

Plant cell undergoing cytokinesis.