Download Chapter 10 Section 10_2 The Process of Cell Division

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
Chromosomes
Prokaryotic Chromosomes
•
Most prokaryotes contain a single, circular DNA chromosome that contains
nearly all of the cell’s genetic information
Chromosomes
Eukaryotic Chromosomes
•
Eukaryotic cells generally have more DNA than prokaryotes and therefore
contain multiple chromosomes
•
Humans cells have 46 chromosomes
Chromosomes
Eukaryotic Chromosomes
•
Chromosomes are located in the nucleus and are made up of chromatin
•
Chromatin is composed of chromosomes and histone proteins
Chromosomes
Eukaryotic 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 Cycle
Prokaryotic 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 Cycle
Eukaryotic Cell Cycle
•
The eukaryotic cell cycle consists of 4 phases: G1, S, G2, and M
The Cell Cycle
Eukaryotic 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 Cycle
Eukaryotic 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 Cycle
Eukaryotic 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 Cycle
Eukaryotic Cell Cycle
•
In eukaryotes, cell division occurs in two main stages:
- Mitosis: the division of the cell nucleus
- Cytokinesis: the division of the cytoplasm
Mitosis
Prophase:
•
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
Mitosis
Prophase:
•
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
Mitosis
Metaphase:
•
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
Mitosis
Anaphase:
•
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
Mitosis
Telophase:
•
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