Transcript Grade 10 Science – The Cell Cycle

Grade 10 Science – The Cell Cycle
Mitosis is cell division that
produces two identical daughter
cells.
Why is cell division important?
There are three reasons:
(1) Reproduction – To produce
new cells
(2) Growth – As multicellular
organisms grow, the number of
cells increases
(3) Repair – Cells need to heal to
stay alive
Grade 10 Science – The Cell Cycle
Mitosis consists of four distinct phases:
(1) Prophase
(2) Metaphase
(3) Anaphase
(4) Telophase.
The cell cycle has two other stages:
(1) Interphase – A long resting, growth
and preparation stage. In this stage,
the DNA strands duplicate.
(2) Cytokinesis – The final stage of cell
division. The CYTOPLASM divides
to produce the two daughter cells.
Grade 10 Science – The Cell Cycle
Interphase
In the interphase stage, the cell is
growing in size and replicating its DNA
in preparation for division. As well, the
nucleus can be easily viewed.
Interphase is the longest stage of the
cell cycle. It is also considered the
“living phase” of the cell, in which the
cell obtains nutrients, grows, reads its
DNA, and conducts other "normal" cell
functions.
Grade 10 Science – The Cell Cycle
Prophase (Phase 1)
This is the first phase of mitosis.
During prophase, the nuclear envelope
around the nucleus starts to break
down and all the chromosomes start to
coil up in the centre of the cell.
Since the DNA strands duplicated
during interphase, each chromosome
consists of two identical strands called
“sister chromatids” held together by a
centromere. An individual strand is a
chromatid.
Grade 10 Science – The Cell Cycle
Metaphase (Phase 2)
During metaphase, the
chromosomes pairs line
up in the middle of the
cell.
A spindle fibre is
attached to each
chromosome. The fibre
will pull a chromosome to
either side of the cell.
Grade 10 Science – The Cell Cycle
Anaphase (Phase 3)
During anaphase, the
centromere splits, and the
spindle fibres become shorter
pulling each chromosome pair
apart and to the opposite ends of
the cell.
From this separation, each
chromosome pair splits into two
identical single-strand parts
Grade 10 Science – The Cell Cycle
Telophase (Phase 4)
The final stage of cell
replication. The chromosomes
become longer and a nuclear
envelope begins to reform
around the chromosomes.
This phase is followed by
Cytokinesis. A new cell wall is
created down the centre and
two daughter cells are formed.
Grade 10 Science – The Cell Cycle
The cell cycle is very
complicated. It is an ordered set
of events culminating in cell
growth and division of the parent
cell into two daughter cells.
This link will help illustrate the
beauty of the cells and various
features of Cell Division and the
Cell Cycle