Mitosis
KEY CONCEPTS
▪ Most cell division results in genetically
identical daughter cells
▪ The mitotic phase alternates with
interphase in the cell cycle
▪ The eukaryotic cell cycle is regulated by a
molecular control system
The Key Roles of Cell Division
→ Where a cell exists, there must have been a
preexisting cell, just as the animal arises only from
an animal and the plant only from a plant.
→ The continuity of life is based on the reproduction
of cells, or cell division.
→ Cell division plays several important roles in life.
→ When a prokaryotic cell divides, it is actually
reproducing, since the process gives rise to a new
organism (another cell).
→ Cell division continues to function in renewal and
repair in fully grown multicellular eukaryotes, Most cell division results in genetically
replacing cells that die from accidents or normal identical daughter cells
wear and tear.
→ The cell division process is an integral part of the → In both prokaryotes and eukaryotes, most cell
cell cycle, the life of a cell from the time it is first division involves the distribution of identical
formed during division of a parent cell until its own genetic material—DNA—to two daughter cells.
division into two daughter cells. → The exception is meiosis, the special type of
→ Passing identical genetic material to cellular eukaryotic cell division that can produce sperm
offspring is a crucial function of cell division. and eggs.
→ A dividing cell replicates its DNA, distributes the
• Cellular Organization of the Genetic Material two copies to opposite ends of the cell, and then
→ A cell’s DNA, its genetic information, is called its splits into daughter cells.
genome.
→ Although a prokaryotic genome is often a single → Together, the entire complex of DNA & proteins
DNA molecule, eukaryotic genomes usually that is the building material of chromosomes is
consist of a number of DNA molecules. (2m of DNA) referred to as chromatin.
→ Before division to form genetically identical → The chromatin of a chromosome varies in its
daughter cells, all of this DNA must be copied, or degree of condensation during the process of
replicated, and then the two copies must be cell division.
separated so that each daughter cell ends up → Every eukaryotic species has a characteristic
with a complete genome. number of chromosomes in each cell’s nucleus.
→ The replication & distribution of so much DNA → The nuclei of human somatic cells (all body cells
are manageable because the DNA molecules are except the reproductive cells)each contain 46
packaged into structures called chromosomes chromosomes, made up of two sets of 23, one
→ The DNA molecule carries several hundred to a set inherited from each parent.
few thousand genes, the units of information → Reproductive cells, or gametes such as sperm
that specify an organism’s inherited traits. and eggs have half as many chromosomes as
→ associated proteins maintain the structure of the somatic cells human gametes have one set of 23
chromosome and help control the activity of the chromosomes.
genes.
, • Distribution of Chromosomes During Eukaryotic
Cell Division
→ When a cell is not dividing, and even as it replicates its
DNA in preparation for cell division, each chromosome
is in the form of a long, thin chromatin fiber.
→ After DNA replication, the chromosomes condense as a
part of cell division: Each chromatin fiber becomes
densely coiled and folded, making the chromosomes
much shorter and so thick that we can see them with a
light microscope.
→ Each duplicated chromosome consists of
two sister chromatids, which are joined copies of the
original chromosome.
→ The two chromatids, each containing an identical DNA
molecule, are typically attached all along their lengths by
protein complexes called ~ cohesins; this attachment is
known as sister chromatid cohesion
→ Each sister chromatid has a centromere, a region made
up of repetitive sequences in the chromosomal DNA
where the chromatid is attached most closely to its
sister chromatid.
→ This attachment is mediated by proteins that recognize
and bind to the centromeric DNA; other bound proteins
condense the DNA, giving the duplicated chromosome
a narrow “waist.”
KEY CONCEPTS
▪ Most cell division results in genetically
identical daughter cells
▪ The mitotic phase alternates with
interphase in the cell cycle
▪ The eukaryotic cell cycle is regulated by a
molecular control system
The Key Roles of Cell Division
→ Where a cell exists, there must have been a
preexisting cell, just as the animal arises only from
an animal and the plant only from a plant.
→ The continuity of life is based on the reproduction
of cells, or cell division.
→ Cell division plays several important roles in life.
→ When a prokaryotic cell divides, it is actually
reproducing, since the process gives rise to a new
organism (another cell).
→ Cell division continues to function in renewal and
repair in fully grown multicellular eukaryotes, Most cell division results in genetically
replacing cells that die from accidents or normal identical daughter cells
wear and tear.
→ The cell division process is an integral part of the → In both prokaryotes and eukaryotes, most cell
cell cycle, the life of a cell from the time it is first division involves the distribution of identical
formed during division of a parent cell until its own genetic material—DNA—to two daughter cells.
division into two daughter cells. → The exception is meiosis, the special type of
→ Passing identical genetic material to cellular eukaryotic cell division that can produce sperm
offspring is a crucial function of cell division. and eggs.
→ A dividing cell replicates its DNA, distributes the
• Cellular Organization of the Genetic Material two copies to opposite ends of the cell, and then
→ A cell’s DNA, its genetic information, is called its splits into daughter cells.
genome.
→ Although a prokaryotic genome is often a single → Together, the entire complex of DNA & proteins
DNA molecule, eukaryotic genomes usually that is the building material of chromosomes is
consist of a number of DNA molecules. (2m of DNA) referred to as chromatin.
→ Before division to form genetically identical → The chromatin of a chromosome varies in its
daughter cells, all of this DNA must be copied, or degree of condensation during the process of
replicated, and then the two copies must be cell division.
separated so that each daughter cell ends up → Every eukaryotic species has a characteristic
with a complete genome. number of chromosomes in each cell’s nucleus.
→ The replication & distribution of so much DNA → The nuclei of human somatic cells (all body cells
are manageable because the DNA molecules are except the reproductive cells)each contain 46
packaged into structures called chromosomes chromosomes, made up of two sets of 23, one
→ The DNA molecule carries several hundred to a set inherited from each parent.
few thousand genes, the units of information → Reproductive cells, or gametes such as sperm
that specify an organism’s inherited traits. and eggs have half as many chromosomes as
→ associated proteins maintain the structure of the somatic cells human gametes have one set of 23
chromosome and help control the activity of the chromosomes.
genes.
, • Distribution of Chromosomes During Eukaryotic
Cell Division
→ When a cell is not dividing, and even as it replicates its
DNA in preparation for cell division, each chromosome
is in the form of a long, thin chromatin fiber.
→ After DNA replication, the chromosomes condense as a
part of cell division: Each chromatin fiber becomes
densely coiled and folded, making the chromosomes
much shorter and so thick that we can see them with a
light microscope.
→ Each duplicated chromosome consists of
two sister chromatids, which are joined copies of the
original chromosome.
→ The two chromatids, each containing an identical DNA
molecule, are typically attached all along their lengths by
protein complexes called ~ cohesins; this attachment is
known as sister chromatid cohesion
→ Each sister chromatid has a centromere, a region made
up of repetitive sequences in the chromosomal DNA
where the chromatid is attached most closely to its
sister chromatid.
→ This attachment is mediated by proteins that recognize
and bind to the centromeric DNA; other bound proteins
condense the DNA, giving the duplicated chromosome
a narrow “waist.”
