Transcript Somatic Cell Division

Somatic Cell Division
Mitosis
Somatic Cells
All body cells except gametes (sex cells)
Somatic Cell Division
A cell divides into two identical cells
Replaces dead or injured cells
Adds new cells for tissue growth
DNA Replication (Duplication)
The DNA sequences that make up the
chromosomes have to be copied so the same
genetic material can be passed on to the
new cells
Cell Cycle
The sequence of changes a cell undergoes
from the time it forms until the time it
duplicates its contents and divides into 2
cells
Two major time periods:
Interphase – not dividing
Mitotic Phase - dividing
Interphase
The cell replicates DNA and manufactures
additional cell organelles and cytosolic
components
High metabolic activity
Most growth
DNA Replication
DNA nucleotides are synthesized in the
cytosol and imported to the nucleus
The helical DNA uncoils and the 2 strands
separate between the base pairs
The exposed base pair on each strand pairs
with a newly synthesized complementary
nucleotide
The new DNA strands take shape as
chemical bonds form
DNA Replication - continued
The original DNA molecule has become 2
identical strands of DNA
Once a cell completes DNA replication, the
mitotic phase can begin.
Mitotic Phase
Mitosis – division of the nucleus
Cytokinesis – division of the cytoplasm
Nuclear Division
The duplicated chromosomes become
divided such that one set ends up in each
nucleus
The process is divided into 4 stages:
Prophase, Metaphase, Anaphase and Telophase
**Mitosis is a continuous process and one phase
merges with the next**
Prophase
Chromatin fibers condense and shorten into
chromosomes
Each prophase chromosome consists of a
pair of identical double stranded chromatids
Mitotic Spindle is formed by the
pericentriolar material and centrioles are
pushed to opposite sides of the cell
The nucleolus and nuclear envelope break
down
Metaphase
The centromeres of the chromatid pairs are
aligned along the center of the mitotic
spindle – this is called the metaphase plate
Anaphase
The centromeres split,
separating the
chromatid pair, which
move to opposite ends
of the cell.
Once separated the
chromatids are called
chomosomes.
Telophase
Final stage of mitosis
Begins when chromosome movement stops
The chromosomes start to uncoil, a new
nuclear envelope forms, nucleoli appear and
the mitotic spindle breaks up.
TWO nuclei are present and the cell starts
to divide into 2
Cytoplasmic Division - cytokinesis
Division of the cell’s cytosol and organelles
Begins in late anaphase/early telophase with
the formation of a cleavage furrow
Cleavage Furrow – slight indentation of the
plasma membrane
Checkpoint
What is the difference between a chromatid
and a chromosome?
In which stage of the cell cycle is the cell
growing?
What are the mitotic phases in order?
What is a major event in each stage?