gRADE 8-

1. Heredity: Inheritance and
Variation of Traits

2. At the end of the lesson, you should be
able to:
1. Compare mitosis and meiosis and their
roles in the cell division;
2. Explain the significance of meiosis in
maintaining the chromosome number;

3. The Cell Cycle and Stages of Mitosis

4. The production of new cells to bring about
growth, replacement of damaged cells in
the wounded body parts, and production of
new generations of individuals among
some groups of organisms take place
through one of the wonderful processes
that happens in the body of living things
called cell division.

6. • Two kinds of cell division take place in our body:
these are mitosis and meiosis.
• Mitosis takes place in our body cells (called
somatic cells)
• Mitosis is responsible for the increase in weight
and height, and responsible for healing of wound.
• Meiosis takes place in the ovaries and testes of
animals, including humans. It is responsible of
gametes or sex cells- sperm cell and egg cell.

7. • Cell Cycle
-New cells are formed through cell division. This is one
important breakthrough that was discovered by Rudolf
Virchow, a German pathologist in 1858.

8. The Interphase
• Nucleus is considered as the control
center of the cell for it directs and
coordinates all cellular activities.
• In the cell division process, the
nucleus plays a very important role
since most of the processes that
happen during cell division are
centered within the nucleus.

9. • Interphases is divided into three suphases,
namely G1, S and G2.
• “G” stands for growth and “S” for synthesis.
• G1 is an initial period of growth “S” comes next.
• It is during this time that the DNA is synthesized
so that the chromosomes can replicate.
• G2 is the time for more growth, and it is also the
subphase that separates interphase from mitotic
or M into similar equal parts.

10. • Stages of Mitosis
Mitosis or M phase is divided into different
stages.
We will use the acronym PMAT to remember the
different stages chronologically. Each stage is
characterized by various events.

11. STAGE 1- PROPHASE
In this stage, the nuclear
membrane and nucleolus
double stranded and are
called chromatids.
The double- stranded
chromosomes are
connected together at one
point by the centromere.
Spindle- fibers later
become well-developed.

12. STAGE 2- METAPHASE
The double-stranded
chromosomes called
chromatids align
themselves at the
equator of the cell.
Each chromatid is
attached to the spindle
by a structure in the
centromere called
kinetochore.

13. STAGE 3- ANAPHASE
• Forces originating from
the poles pull the
chromatids to move.
Consequently, centromere
splits, which separates the
chromatids into new,
single- stranded
chromosomes. The
chromosomes then
migrate toward their
respective poles.

14. STAGE 4- TELOPHASE
This is the final stage of
mitosis. The chromosomes
now have reached the
opposite poles, and the
spindle disappears.
At the poles, the
chromosomes uncoil and
the nucleolus and nuclear
membrane begin to reform.
The cytoplasm divides and
plasma membrane divides
the cell into two.

15. Remember that during mitosis, two things
happen.
First, the nucleus divides (called
karyokinesis); second, the cytoplasm divides
(called cytokinesis).
The whole process takes about 5 to 10
minutes as in the case of some animal
embryos and 20 minutes in a dividing
bacterium.

16. Comparison of Mitosis in Plant and Animal Cells
Animal cell have centrioles, which are absent in plant
cells.
During prophase, the centriole splits into halves and
both travel toward the opposite side of the nucleus.
During cytokinesis that leads to the formation of a new
plasma membrane.
In animal cells, cytokinesis is marked by the appearance
of a cleavage furrow, a constriction that begins on both
sides of the cell moving inward toward the center.

17. • In plant cells, cytokinesis is marked by the formation
of a cell plates that forms at the middle, growing
outward until the two new daughter cells are
formed.