by Sophie Dartnell
0.0 stars - 0 reviews
range from 0 to 5
The growth and division of cells (mitosis) and the formation of sperm and eggs
(meiosis) are important for almost all organisms. We all began as a single cell that
resulted from our father’s sperm fertilizing our mother’s egg. This single cell then
divided by mitosis into two cells (daughter cells) which then grew and divided into
four cells. This process of mitosis continued until we were born. It then continued
again until we were “grown up”. It is still happening right now as some of our cells use
mitosis to replace old dead cells, such as skin cells.
- When cells divide they must pass on all of
their genetic information to each daughter cell.
Therefore, each chromosome must be
replicated before cell division so that each
cell receives all the instructions it
needs to function.
- When a chromosome is replicated the two
identical chromosomes are joined together by
a centromere and they are called
- During mitosis, the cell separates its
cytoplasm, organelles and DNA
- Mitosis is a continuous process but it is
useful to divide it into four stages: prophase,
metaphase, anaphase, and telophase.
- During prophase, the nuclear membrane
disappears and a framework of microtubules is
The microtubules form spindle fibers that
originate at the poles. Some spindle fibers span
the entire cell and others attach to the chromosomes.
The spindle fibers function to move the
- During metaphase, each chromosome is positioned
along the central axis of the cell called the metaphase
plate. The centromeres are situated directly along the
metaphase plate with the each chromatid positioned
on opposite sides of the metaphase
plate. The cell begins to elongate.
- During anaphase, each centromere splits
into two, causing sister chromatids to
Once separated, each chromatid is considered a
chromosome and the once-joined sisters are pulled to
opposite poles of the cell by the microtubules. Also
during anaphase, the entire cell begins to elongate and,
therefore, further separates the sister
- At telophase, a daughter nuclei begins to form at
each pole, enveloping the gathered
Finally during cytokinesis, the cytoplasm divides
resulting in two genetically identical daughter
2.5.1 Outline the stages in the cell cycle,
including interphase (G1, S, G2), mitosis and
Session Rule 1
Session Rule 2
Define Action Points
2.5.6 State that growth, embryonic development,
tissue repair and asexual reproduction involve
The zygote undergoes rapid mitotic divisions with no significant growth and cellular
differentiation, leading to development of an embryo.
Position the three embryonic germ layers, the endoderm, ectoderm and
mesoderm. These layers later develop into certain bodily systems.
The ectoderm develops into the skin, nails, the epithelium of the
nose, mouth and anal canal; the lens of the eye, the retina and the
The endoderm develops into the inner linings of the digestive tract, as well as the
linings of the respiratory passages. It also forms many glands, such as the liver and
Give rise to the muscles, circulatory
and excretory systems of the body.
Adult skin consists of two tissue layers: a keratinized stratified epidermis and an
underlying thick layer of collagen-rich dermal connective tissue providing support.
Hairs and glands are derived from, and linked to, the epidermis but project deep
into the dermal layer.If a tissue is damaged or a cell is dead; mitosis regulates the
cell division producing the new cells, New node
Making of a new organism without the fusion of a sperm and egg. Without sex.
Only one parent.
All offspring are identical to the parent.
Making of new and more of body cells. Skin cells making new skin cells. Muscle cells making new muscle cells.
2.5.2 State that tumours (cancers) are the
result of uncontrolled cell division and that
these can occur in any organ or tissue.
Interphase - the nucleolus and the nuclear envelope are distinct and the chromosomes are in the the form of threadlike chromatin.
Prophase- the chromosomes appear condensed, and the nuclear envelope is not apparent.
Metaphase - thick, coiled chromosomes, each with two chromatids, are lined up on the metaphase plate.
Anaphase - the Chromatids of each chromosome have separated and are moving toward the poles
Telophase - the chromosmes are at the poles and are becoming more diffused. The nuclear envelope is reforming. The cytoplasm may be dividing.
Cytokinesis- Division into two daughter cells is completed
Interphase - the nucleolus
Sub Idea 1
Sub Idea 2
New node, New node