Cell Division and Cell Cycle

Cell Division and Chromosomes

• Multicellular eukaryotic organisms require a continuous supply of new cells for growth, development, and repair.
• The cell cycle is the process through which new cells are generated, and it consists of three main stages: growth, DNA replication, and mitosis and division (also known as cytokinesis).

The Cell Cycle

• The first stage of the cell cycle is growth, where the cell increases in size and the number of subcellular structures it contains, such as mitochondria and ribosomes.
• The second stage is DNA replication, where the DNA is duplicated so that the two new cells will each have a full set of DNA.
• The third stage is mitosis and division, where the duplicated chromosomes separate and the cell divides into two daughter cells.

Chromosomes

• Chromosomes are condensed packets of DNA that contain a large number of genes, which control the development of different characteristics.
• Eukaryotic cells have two copies of each chromosome, which are referred to as a pair, one from each parent.
• Humans have 23 pairs of chromosomes, for a total of 46 chromosomes.
• The number of chromosomes varies between species, which is one reason why animals of different species cannot reproduce to have fertile offspring.

Mitosis

• During mitosis, each of the 46 chromosomes duplicates, resulting in two identical copies (an X-shaped chromosome) that are attached to each other.
• The right half of each X-shaped chromosome is a duplicate of the left half.
• T 4he6 chromosomes line up along the center of the cell, and fibers from either side of the cell attach to their respective half of each chromosome, pulling the arms of the chromosomes to opposite sides of the cell.
• This process breaks the chromosomes in half, resulting in two separate arms for each chromosome.

Cytokinesis

• The final stage of the cell cycle is cytokinesis, where the cell membrane and cytoplasm pull apart, forming two daughter cells.
• Each daughter cell receives half of the chromosomes, resulting in identical DNA and identical cells to the parent cell.
• The resulting daughter cells can then contribute to growth, development, or repair and undergo the cell cycle again.

Cell Division and Chromosomes

• Multicellular eukaryotic organisms require a continuous supply of new cells for growth, development, and repair.
• The cell cycle consists of three main stages: growth, DNA replication, and mitosis and division (also known as cytokinesis).

The Cell Cycle

• The first stage of the cell cycle is growth, where the cell increases in size and the number of subcellular structures it contains, such as mitochondria and ribosomes.
• The second stage is DNA replication, where the DNA is duplicated so that the two new cells will each have a full set of DNA.
• The third stage is mitosis and division, where the duplicated chromosomes separate and the cell divides into two daughter cells.

Chromosomes

• Chromosomes are condensed packets of DNA that contain a large number of genes, which control the development of different characteristics.
• Eukaryotic cells have two copies of each chromosome, which are referred to as a pair, one from each parent.
• Humans have 23 pairs of chromosomes, for a total of 46 chromosomes.
• The number of chromosomes varies between species, which is one reason why animals of different species cannot reproduce to have fertile offspring.

Mitosis

• During mitosis, each of the 46 chromosomes duplicates, resulting in two identical copies (an X-shaped chromosome) that are attached to each other.
• The right half of each X-shaped chromosome is a duplicate of the left half.
• The 46 chromosomes line up along the center of the cell, and fibers from either side of the cell attach to their respective half of each chromosome, pulling the arms of the chromosomes to opposite sides of the cell.
• This process breaks the chromosomes in half, resulting in two separate arms for each chromosome.

Cytokinesis

• The final stage of the cell cycle is cytokinesis, where the cell membrane and cytoplasm pull apart, forming two daughter cells.
• Each daughter cell receives half of the chromosomes, resulting in identical DNA and identical cells to the parent cell.
• The resulting daughter cells can then contribute to growth, development, or repair and undergo the cell cycle again.