Topic 2: Cells
Learning Opportunity
Cell Cycle
Outline the stages in the cell cycle including interphase (G1, S, G2), mitosis and cytokinesis
The life cycle of a cell is known as the __________________________ and consists of several different stages. The
cell will spend a certain amount of time each in each stage depending on what type of cell it is. For cells that
are actively growing and dividing (like skin cells), the entire cell cycle can be completed in about 24 hours.
Other cells, such as certain types of nerve cell, will never fully complete the cell cycle as they do not divide.
The Cell Cycle
The first phase in the cell cycle is known as ___________________________. During interphase, the cell
is ___________ _______________________________________________________. Cells spend about 90% of their lives in
interphase, which can can be broken down into 3 stages:
G1 phase
During this time there is
(or gap 1)
S (synthesis)
The cell prepares for division;
G2 phase
there is _________________
(or gap 2)
an _____________________________
Nuclear Division
________________ this ensure
that there are the same
number of chromosomes
from cell to cell
________________ and the rest of
the cell
Mitosis - Key Terms
Before we go into any more detail on the process of mitosis, it is important to review a few key terms:
As you know, inside the nucleus of every cell is DNA. When the cell is in interphase of the cell cycle, that
DNA is in a form known as ________________________. Chromatin refers
to ___________________________________________________ in the nucleus during _________________________. Remember
learning that prokaryotic cells have "naked DNA"? That's because their DNA is not wrapped around proteins
to make it compact like the DNA of eukaryotic cells. Think of chromatin like spaghetti and meatballs - the
is an
active period
in proteins are the meat balls you can wrap the spaghetti
long State
of interphase
DNA are the
and the
the life of a cell when many metabolic
reactions occur, including protein synthesis,
an increase in the
the image
number of mitochondria and/or chloroplasts
Topic 2: Cells
When the cell is about to start mitosis, the now
replicated DNA
will ___________________________________itself into
structures called ____________________________. This will
keep things nice and _______________________ in the
nucleus. If chromatin is like spaghetti and meatballs,
Learning Opportunity
think of chromosomes like fusili pasta. When the cell enters mitosis, each chromosome is made up of two
partners - the original DNA and its duplicate.
The _____________________________refer to the _______ _________________________________________________. They are
completely identical. One chromatid is the original DNA and one is the duplicate.
This is ______________________________________________________.
The first phase of mitosis is known as ____________________. During this phase, the following events occur:
- chromatin fibres ______________________
(become more tightly coiled to become
- _______________________________ to opposite
- _________________________________ (made of
microtubules) and attach to chromosome’s
- nuclear membrane starts to _________________
- chromosomes _________________________
- centromeres of each chromosome lie on
the plate
- nuclear membrane completely dissolves
Topic 2: Cells
Learning Opportunity
- centromeres divide and __________________
- chromosomes ____________________________ as
microtubules shorten
- centromeres move towards poles first
because they are attached to the
- identical set of chromosomes moves to
each pole
to each pole
- chromosomes _____________________________
- spindle fibres dissolve
- _________________________________________
Can you identify cells in the different stages of mitosis?
Try this:
After mitosis
After the nucleus has divided, now the rest of the cell will too in a process known as cytokinesis. In animal
cells the cytoplasm divides, pinching inwards to form cleavage furrow. In plants a new cell wall forms and
separates the two cells.
Explain how mitosis produces two genetically identical nuclei
One of the purposes of mitosis is two create genetically IDENTICAL nuclei. This is able to be accomplished
because during the S-phase, ________________________________________________________________. Therefore just prior
to the beginning of mitosis there is actually ________________________________________________________________in a
cell. Each chromosome in this state is represented by a pair of sister chromatids. These sister chromatids are
then separated in anaphase as the spindle microtubules attaches to centromere and pulls the sister
chromatids to opposite poles. As the sister chromatids separate they are called chromosomes. This means
that ____________________________________ ____________________________.same genetic material).
State that growth, embryonic development, tissue repair and asesxual reproduction involve
mitosis (2.5.6)
The following processes would not be possible without mitosis:
State that tumours (cancers) are the result of uncontrolled cell division and that these can occur in
any organ or tissue (2.5.2)
As we have previously discussed, cancer is a group of diseases associated
with ____________________________________ ___________________________________________.