Chapter 10: Cell Growth and Division

10.2 - The Process of Cell Division

Mr. M. Varco Saint Joseph High School

Chromosomes• What role do chromosomes have in cell division?

• Prior to cell division, parent cells must undergo DNA replication so that each daughter cell gets a complete copy of genetic information.

• All cells, including bacteria, have a tremendous amount of DNA that must be carefully packaged.

Chromosomes• The cell’s genetic information is bundled into packages of DNA known as

chromosomes

• Chromosomes make it possible to separate DNA precisely during cell division

• The cells of every organism have a specific # of chromosomes

ChromosomesProkaryotic Chromosomes

• Most prokaryotes contain a single, circular DNA chromosome that contains nearly all of the cell’s genetic information

ChromosomesEukaryotic Chromosomes

• Eukaryotic cells generally have more DNA than prokaryotes and therefore contain multiple chromosomes

• Humans cells have 46 chromosomes

ChromosomesEukaryotic Chromosomes

• Chromosomes are located in the nucleus and are made up of chromatin

• Chromatin is composed of chromosomes and histone proteins

ChromosomesEukaryotic Chromosomes

• DNA tightly coils around histone proteins, forming nucleosomes

• Cells package their information in chromosomes to ensure equal division of DNA when a cell divides

The Cell Cycle• During the cell cycle, a cell: grows, prepares for division, and divides to form

two daughter cells

The Cell CycleProkaryotic Cell Cycle

• The prokaryotic cell cycle is a regular pattern of growth, DNA replication, and cell division

• The process of cell division is a form of asexual reproduction called binary fission

The Cell CycleEukaryotic Cell Cycle

• The eukaryotic cell cycle consists of 4 phases: G1, S, G2, and M

The Cell CycleEukaryotic Cell Cycle

• During the G1 phase, cells do most of their growing, which includes increasing in size, as well as synthesis of proteins and organelles

The Cell CycleEukaryotic Cell Cycle

• During the S phase, new DNA is synthesized when the chromosomes are replicated.

• The cell contains twice as much DNA as it did at the beginning of the cell cycle

The Cell CycleEukaryotic Cell Cycle

• During the G2 phase, many of the organelles and molecules required for cell division are reproduced

• The is the shortest of the three phases, and marks the cell as ready for division

The Cell Cycle

Eukaryotic Cell Cycle

• The M phase, which follows interphase, produces two daughter cells

• Unlike interphase, the process of cell division occurs very quickly

The Cell CycleEukaryotic Cell Cycle

• In eukaryotes, cell division occurs in two main stages:

- Mitosis: the division of the cell nucleus

- Cytokinesis: the division of the cytoplasm

MitosisProphase:

• The first phase of mitosis, in which chromatin condense and become visible chromosomes

• The duplicated strands of DNA attach at an area called the centromere

• Each DNA strand in the duplicated chromosome is referred to as a chromatid

MitosisProphase:

• The cell starts to build a spindle, used to help separate the chromosomes at the centromere

• Spindle fibers extend from regions where tiny paired structures called centrioles are located

MitosisMetaphase:

• The second phase, where centromeres of the duplicated chromosomes line up across the center of the cell

• Spindle fibers connect the centromere of each chromosomes to the two poles of the spindle

MitosisAnaphase:

• The third phase, when centromeres are pulled apart and the sister chromatids separate to become individual chromosomes

• The chromosomes move along spindle fibers to opposite ends of the cell

MitosisTelophase:

• The forth phase, during which the chromosomes begin to spread out into a tangle of chromatin

• Spindle fibers break apart, and the nuclear envelope re-forms around each cluster of chromosomes