Science 8

Quarter 4
Self-Learning Module 5
Meiosis
 EXPECTATIONS

This module is designed and written to help you master the lesson on how sex
cells; sperm cell and egg cell divides for reproduction through the different stages of
cell division called meiosis.

It has prepared to provide activities for reinforcement, strengthening and

enriching knowledge and skills. The skills in this module cover all the most essential
learning competencies in the list issued by the Department of Education.

This module uses different and interesting approaches, strategies, and

techniques to further hone scientific understanding of the learners. The module is
about the changes that occur in each stage of meiosis, difference between sperm and
egg cell production and the important role of meiosis.

After going through this module, you are expected to:

1. describe the changes that occur in each stage of meiosis,

2. make graphic organizer to differentiate spermatogenesis and oogenesis,
3. and appreciate the significance of meiosis in reproduction, variation and
in maintaining the chromosome number of species.

PRETEST

Instructions: Choose the letter of the best answer. Write the chosen letter on a
separate sheet of paper.

1. What is the type of cell division that produces gametes and prepares the
organism for fertilization during sexual reproduction?
a. cytokinesis
b. meiosis
c. mitosis
d. synapsis

2. What do you call the pairing of homologous chromosomes in Prophase I?

a. crossing-over
b. cytokinesis
c. synapsis
d. variation
 3. Which of the following is FALSE about oogenesis?
a. Oogenesis begins during fetal development.
b. Oogenesis produces haploid cell unidentical to the parent cell.
c. Puberty in the female triggers primary oocytes to continue their
development.
d. Oogenesis produces one primary oocyte, two secondary oocytes and
four ova from one oogonium.

4. If there are four spermatogonia, how many secondary spermatocytes will be

produced after meiosis?
a. 8 secondary spermatocytes
a. 4 secondary spermatocytes
b. 2 secondary spermatocytes
c. 1 secondary spermatocyte

5. Which of the following feature of meiosis ensures that the number of

chromosomes in organism stays constant generation after generation?
a. Meiosis results to the production of haploid daughter cells.
b. Each daughter cell in meiosis receives a copy of each kind of
chromosome.
c. Variations in characteristics among daughter cells allow organism to
adapt to the changing environment.
d. Crossing-over and independent assortment of chromosomes during
fertilization ensure that the chromosomes are distributed to the
daughter cells in various combination.

RECAP
Previously we have discussed about the stages of cell cycle and how we
produce body cells (somatic cells) in a process we called mitosis. Let us have a short
review by identifying the stage of mitosis in the following illustrations.

1. 2. 3. 4.

Excellent! You already know the different stages of mitosis and I am sure the
important events in each stage as well. Today, we will be discussing about the other
type of cell division. Let us begin!
 LESSON

Every species has a specific number of chromosomes. The chromosomal

number is either diploid number (2N) or haploid number (N). Diploid means the
nucleus of a cell contains two sets of homologous chromosomes, half of which are
given by a female organism and the other half from the male organism. Homologous
chromosomes are pair of chromosomes having the same appearance carrying both
the genes that control the same traits except for reproductive or sex cells (gametes)—
egg cell and sperm cell. Gametes are haploid in number. Haploid cells contain
chromosomes in single set; thus, it is equal to the half of the diploid number. Look
at the following illustrations to better understand homologous chromosome, haploid
and diploid.
E HAPLOID DIPLOID
A B D
C

https://commons.wikimedia.org/wiki
https://pixabay.com/vectors/chromosomes-genetics-
/File:Haploid_vs_diploid_af2.png
metacentric-156403/

Which pair/s of chromosomes is/are What is the haploid (N)

homologous chromosomes? Yes, these chromosomal number?
are A, C and E. Correct 3!
Pairs B and D are called Analogous How about the diplod (2N)
Chromosomes. number? Very good, it’s 6!

Check out this table of some species and their constant chromosomal number:

Diploid Number (2N) Haploid Number (N)

Fruit fly 8 4
Dog 78 39
Human 46 23
Humans have 46 chromosomes; 23 of these came from the father’s sperm cell
while the other 23 from the mother’s egg cell. During sexual reproduction, the
haploid sperm cell (N=23) unites with a haploid egg cell (N=23) to form a fertilized egg
or zygote, which is diploid (2N= 46). The zygote will grow and develop into a
multicellular adult by mitosis. For sexual reproduction to happen, gametes (egg and
sperm cell) which are haploid must always be available. What makes it possible to
produce haploid cells? The answer is MEIOSIS!

Stages of Meiosis
Just like mitosis, meiosis stars with an interphase as well as the other stages
of cell division as what we have been discussed in the previous module. But, in
meiotic division, the parent cell divides twice in which we called Meiosis I and Meiosis
II. Each meiotic division, Meiosis I and II have stages Prophase, Metaphase,
Anaphase and Telophase. Study the diagram of meiosis below.
 https://commons.wikimedia.org/wiki/File:Meiosis_Stages.svg

The major difference between mitosis and meiosis occurs in the Prophase I
stage of Meiosis I. Notice that in meiosis, chromosomes pair with their homologues.
The homologous chromosomes pair and intertwine in the process we called,
synapsis. As the synapsis occurs, non-sister chromatids (refer to the diagram)
overlaps and exchange genetic material, a process now we called as crossing-over.
It results to the change in genetic recombination (genetic material between parent
cell and daughter cells will not be strictly identical) this event leads to variation.

Sister chromatids

Non-sister
chromatids

https://commons.wikimedia.org/wiki/File:Figure_11_01_02.jpg

In Metaphase I, homologous chromosomes at the equatorial plate then

undergo Anaphase I and Telophase I. Take note that the number of chromosomes in
each daughter cell after Meiosis I is now reduced into half or haploid in number.
Then each cell will now proceed to Meiosis II passing once again through the stages;
Prophase II, Metaphase II, Anaphase II and Telophase II. Since the cell now is in
haploid number unlike in Meiosis I where the parent cell is diploid, each cell will now
produce 2 haploid daughter cells, so that all in all there are four haploid daughter
cells produced at the end of the entire process of Meiosis.

Importance of Meiosis
All organisms have diploid number of chromosomes. Without Meiosis, the
chromosomal number will continue to increase. Hence, meiosis ensures that all the
chromosome number of organisms remains the same generation after generation.
Meiosis also safeguards that each daughter cell receives a copy of each kind
of kind of chromosomes; thus, each daughter cell would receive each kind of genes.
The occurrence of crossing-over and the independent-assortment of chromosomes
during fertilization ensure that the chromosomes are distributed to the daughter
cells in different combinations, bringing about remarkable variations in the
characteristics of the organisms. These variations in characteristics is very helpful
for the organisms to adapt in their changing environment.
Meiosis and Sex Cells

Gametogenesis is the process where sex cells undergo meiosis to form sperm
cells (spermatogenesis) in male and egg cells (oogenesis) in female.

Spermatogenesis- The production of sperm by the

process of meiosis. It begins at the age of puberty
(13-16 years of age) and continues until old age.
Starting from a diploid (2N) spermatogonia (sing.
spermatogonium) that will actively divide by mitosis
so that there will be continuous supply of sperms
all throughout a male’s life. The male hormones
stimulate the growth of spermatogonia. One (1)
spermatogonium will differentiate into 1 primary
spermatocyte. At puberty, this one primary
spermatocyte divide by means of Meiosis I to
produce 2 haploid secondary spermatocytes. The
secondary spermatocytes undergo Meiosis II and
each cell produces two spermatids that are haploid
(N). This result to a total of 4 spermatids that will
mature into 4 sperm cells. The entire process of
https://commons.wikimedia.org/
spermatogenesis results to 4 haploid sperm cells wiki/File:Figure_43_03_05.jpg
from 1 diploid spermatogonium.

Oogenesis- The process of producing egg cells by

means of meiosis. The production of oogonia by
means of mitosis begins during the prenatal stage
in the development of a human female. The
produced oogonia will be released in its lifetime.
Meiosis I begins at nearing a birth of a human
female. In Meiosis I, one (1) oogonium transformed
into 1 primary oocyte which remains at this stage
until the female is born and reach puberty. As
Meiosis I finally complete, a primary oocyte divides
into 2 haploid (N) cells of unequal sizes. The large
cell is called secondary oocyte and the small one is
called first polar body. Both cells enter Meiosis II,
and the division process occurs again. The
secondary oocyte divides again into 2 unequal sizes:
a haploid ovum or egg cell and second polar body.
The first polar body also divided into 2 polar bodies. https://www.toppr.com/ask/que
stion/in-spermatogenesis-a-
All the polar bodies will soon degenerate. The entire primary-spermatocyte-produce-
process of oogenesis results to only 1 haploid ovum four-similar-sperms-while/; a
or egg cell from 1 diploid oogonium.
 ACTIVITIES

ACTIVITY # 1
PHASES OF MEIOSIS
Direction: Study the illustration of the stages of meiosis below and complete the table
that follows.

https://commons.wikimedia.org/wiki/File:Meiosis_Stages_-_Numerical_Version.svg

1 2 3 4 5 6 7 8

Name of
Phase
Important
Event in
this
Phase

ACTIVITY # 2
THE BEGINNING
Direction: Choose from the “tiles” below to make a graphic organizer showing the
similarities and differences of spermatogenesis and oogenesis.

Spermatogenesis Both Oogenesis

produce sex produces produces

involves 1 haploid 4 haploid
cells with begins
the sex cell begins sex cells
only half the during
fetal division from 1 during from 1
number of
develop of sex diploid puberty diploid
its parent
-ment cells parent parent
cell
cell cell
 ACTIVITY # 3
“NAY” OR “YAY”

Direction: Read carefully the following statements. Tick ( ) the “YAY” column if it
describes the importance of meiosis and “NAY” if it is not.

1. If sex cells won’t divide through Meiosis, the chromosomal

number will continue to increase.
2. Meiosis ensures that all the chromosome number of organisms
changes from generation to generation.
3. Meiosis safeguards that each daughter cell receives a copy of each
kind of kind of chromosomes; thus, each daughter cell would receive
each kind of genes.
4. The crossing over and independent assortment bring about
remarkable variations in the characteristics of the organisms.
5. Variations in characteristics among organisms is not important
in adapting to the changing environment.

WRAP-UP

To summarize what we you have learned from this module, write the
chromosomal number of the cell in each stage of meiosis whether diploid (2N) or
haploid (N).

https://commons.wikimedia.org/wiki/File:Meiosis_Stages_-_Numerical_Version.svg
 VALUING
The diagram on the left shows the life
cycle of human and the importance of
meiosis in maintaining the chromosome
number in 46 chromosomes as diploid
number.

From a diploid parent, haploid egg cell

(N= 23) and sperm cell (N=23) will unite to
form a diploid zygote (2N that develops into
fetus until a baby is born and grows into an
adult and the cycle goes on and on. This
ensures that human beings will not be
https://commons.wikimedia.org/wiki/File: extinct.
Biological_Life_Cycle_of_Humans.svg

POSTTEST

Instructions: Choose the letter of the best answer. Write the chosen letter on a
separate sheet of paper.

1. Which of the following BEST describes meiosis as a type of cell division?

a. It involves the division of body cells.
b. It involves the division of sperm cell and egg cell.
c. It is the division of sex cells to produce haploid daughter cells.
d. It is the division of sex cells to produce diploid daughter cells.

2. What do you call the exchange of genetic material between non-sister

chromatids of homologous chromosomes at Prophase I?
a. variation
b. synapsis
c. cytokinesis
d. crossing over

3. If there are 2 oogonia, how many ova or egg cell will be produced after
meiosis?
a. 1 egg cell
b. 2 egg cells
c. 3 egg cells
d. 4 egg cells
4. Which of the following statement is FALSE about spermatogenesis and
oogenesis?

a. Spermatogenesis and oogenesis are both the division of somatic or body

cells.
b. Spermatogenesis and oogenesis are both the division of gametes or sex
cells.
c. Spermatogenesis and oogenesis are meiotic division of sex cells.
d. Spermatogenesis and oogenesis produce haploid sex cells.

5. Which of the following important event in meiosis explains the variation in

characteristic among organisms?
a. The exchange of genetic material between non-sister chromatids of
homologous chromosomes.
b. The reception of a copy of each kind of chromosome by each daughter
cell.
c. The pairing of homologous chromosomes during Prophase I.
d. The production of haploid daughter cells.