General Biology 1
Quarter 3 – Module 4:
Cell Cycle: Meiosis
General Biology 1 – Grade 11
Alternative Delivery Mode
Quarter 3 – Module 4: Cell Cycle: Meiosis
First Edition, 2020
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General Biology 1
Quarter 3 – Module 4:
Cell Cycle: Meiosis
Introductory Message
This Self-Learning Module (SLM) is prepared so that you, our dear learners,
can continue your studies and learn while at home. Activities, questions, directions,
exercises, and discussions are carefully stated for you to understand each lesson.
Each SLM is composed of different parts. Each part shall guide you step-bystep as you discover and understand the lesson prepared for you.
Pre-tests are provided to measure your prior knowledge on lessons in each
SLM. This will tell you if you need to proceed on completing this module or if you
need to ask your facilitator or your teacher’s assistance for better understanding of
the lesson. At the end of each module, you need to answer the post-test to self-check
your learning. Answer keys are provided for each activity and test. We trust that you
will be honest in using these.
In addition to the material in the main text, Notes to the Teacher are also
provided to our facilitators and parents for strategies and reminders on how they can
best help you on your home-based learning.
Please use this module with care. Do not put unnecessary marks on any part
of this SLM. Use a separate sheet of paper in answering the exercises and tests. And
read the instructions carefully before performing each task.
If you have any questions in using this SLM or any difficulty in answering the
tasks in this module, do not hesitate to consult your teacher or facilitator.
Thank you.
2
What I Need to Know
This module is designed for you to learn about the exciting world of cell preparation
and cell formation as part of the cell cycle. You will dwell and study how cells are
formed. You will also explore the distinctions between and among the phases of
meiotic cellular division. In this module, you will also have to reflect on the
importance of meiosis.
At the end of this module, you are expected to:
1. characterize the phases of the cell cycle and their control points (STEM_BIO11/12
– Id – f – 6).
2. describe the stages of meiosis given 2n = 6 (STEM_BIO11/12 – Id – f – 7);
3. discuss crossing over and recombination in meiosis (STEM_BIO11/12 – Id – f –
8);
4. explain the significance or applications of meiosis (STEM_BIO11/12 – Id – f – 9);
and
5. identify disorders and diseases that result from the malfunction of the cell during
the cell cycle (STEM_BIO11/12 – Id – f – 10).
3
What I Know
You have learned already and have enough background about cell cycle and cell
division. To test your prior knowledge about the said topics, the activity below is
provided for you. All you must do is to match each term in Column A with the correct
description in Column B. Write only the letter that corresponds to the final answer
on the line before each number
Column A
Column B
_____1. Diploid
a. Darkly – staining finite bodies
within
the
nucleus
of
a
eukaryotic cell
b. Threadlike
forms
of
chromosomes
c. Body cells
d. Fusion of sex cells during
fertilization
e. Chromosomes that determine the
gender of an organism
f. A fragment of DNA strand that
codes for a trait
g. Chromosomes that are exactly
alike in size and location of
centromere
h. Cell that contains two complete
sets of chromosomes
i. Reproductive cells
j. Pinching in of the plasma
membrane
k. One half of a chromosome
l. Filamentous bodies that are
involved in the movements of
chromosomes
m. Cell with only one complete set of
chromosomes
n. Body chromosomes
o. Two identical chromatids of a
chromosome
_____2. Gamete
_____3. Homologous chromosomes
_____4. Cleavage furrow
_____5. Gene
_____6. Chromatid
_____7. Sex chromosomes
_____8. Spindle fibers
_____9. Sexual reproduction
_____10. Haploid
_____11. Somatic cells
_____12. Autosomes
_____13. Chromatin materials
_____14. Sister chromatid
_____15. Chromosomes
4
Lesson
1
Cell Cycle: Meiosis
When the sea star loses its arm, it grows a new one.
The lost arm’s cells can also divide to form a whole
new star. When an offspring is produced by only one
parent, the process is called asexual reproduction.
Asexual reproduction is a result of mitotic cell
division. Many types of organisms, including bacteria,
protists, fungi, plants, and some animals can
perpetuate their own species through asexual
reproduction. During asexual reproduction, cell
division (mitosis) replicates the chromosomes of one parent cell. Since the progeny
(offspring) is produced by only one parent, the offspring is genetically identical to its
parent.
Many plants and animals, including humans, are the results of a different kind of
reproduction – sexual reproduction. In sexual reproduction, the genetic material of
one parent is blended with that of the other parent producing a genetically distinct
progeny. Sexual reproduction includes a special form of cell division in which the
number of chromosomes is reduced.
You may recall that the body cells (somatic cells) of
every species have a characteristic number of
chromosomes.
Humans
have
23
pairs
of
chromosomes, a total of 46 chromosomes encased in
each body cell. Any cell that contains two complete
sets of chromosomes is called a diploid cell,
designated by the algebraic notation 2n. Almost all of
the cells in your body are diploid cells. Human sex
cells (gametes, germ cells, or reproductive cells) – the
egg and sperm cells that combine to produce offspring – contain only 23
chromosomes, half the number of a diploid cell. A cell with only one complete set of
chromosomes is called a haploid cell, designated by the algebraic notation n.
All diploid cells, body cells, develop by mitosis. Haploid cells, which are the sex cells,
are produced by a process called meiosis. Meiosis is a process of cell division in
which diploid cells divide to produce genetically distinct haploid cells. Over
generations, meiosis maintains a stable number of chromosomes by producing
gametes that have one set of chromosomes instead of two.
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What’s In
Let us first have a short recap of the applications of cell cycle and meiosis so you can
better understand the significance of meiotic cell division.
Below is a simple activity that can lead you to rationalize some thought – provoking
questions.
1. Why is it important that gametes be haploid cells?
2. What is the advantage of sexual reproduction to a population whose
environment changes?
3. What is in meiosis that accounts for the variation of traits?
4. Organisms such as certain plants, fungi, and algae have the ability to
reproduce either sexually or asexually. What would be the advantage of
having both abilities?
Notes to the Teacher
This module aims to familiarize the students about the significance
of cell cycle and meiosis. Point out the role of meiotic cell division
in chromosomal stability and genetic variability.
What’s New
Almost all cells in an organism contain two complete sets of chromosomes.
Reproductive cells contain only one set. Cells produced by mitosis are diploid while
meiosis produces haploid cells. Haploid and diploid are designated by the algebraic
notation n and 2n, respectively. The table on the next page shows the haploid or
diploid numbers of a variety of organisms. Complete the table and use it to answer
the given questions.
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Organism
n
Amoeba
25
Chimpanzee
24
Earthworm
18
Fern
Hamster
2n
1010
22
Honeybee
32
Human
46
Onion
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1. What are the haploid numbers for the two plants listed in the table?
2. Based on the table above, which organism’s diploid numbers are closest to
that of a human?
3. Explain why a diploid number is always even.
4. Which organism’s haploid and diploid numbers do you find most surprising?
Why?
5. Why is it important that each organism has specific number of chromosomes?
What is It
It has been said already that meiosis is a type of cell division which results in the
formation of gametes with half the number of chromosomes in the body cells. Many
of the stages of meiosis closely resemble corresponding stages in mitosis. Meiosis,
like mitosis, is preceded by the duplication of chromosomes. However, this single
duplication is followed by two consecutive divisions, called meiosis I and meiosis II.
These two cellular divisions result in four genetically distinct daughter cells, each
with a haploid set of chromosomes.
Meiosis is preceded by interphase just like in mitosis. During interphase, the cell
grows and its genetic materials duplicate. As the cell enters meiosis I, also called as
first meiotic division, the chromosome number of the cell is reduced to half of its
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original. After reducing the chromosome number to half, the cell will enter meiosis
II, also called as second meiotic division. Meiosis II is essentially the same as
mitosis. The significant distinctive feature is that meiosis II starts with cells having
half the number of chromosomes of their parent cell. In this meiotic division, the
conservation of chromosome number of the resulted cells in meiosis I happens.
How does the cell prepare for meiosis I while in interphase?
Interphase is the part of the cell cycle through which
the cell undergoes normal growth processes while
also preparing for cell division. For a cell to move from
interphase into meiotic cell division, many internal
and external conditions must be met. Interphase has
three stages based on the metabolic activity taking
place in the cell: G1 (first gap), S (synthesis stage), and
G2 (second gap).
First Gap (G1)
During G1, the cell actively produces ATP, RNA, and protein. Also, during this stage,
the cell increases in size.
Synthesis Stage (S)
During the S stage, the chromosomes, specifically their DNA, replicate.
Second Gap (G2)
During G2, the cell organelles duplicate. Also, the chromosomes uncoil to form the
chromatin materials, which will then turn into granules. Chromatin materials are
thread-like form of chromosomes.
What are the phases of meiosis I?
Prophase I
As the cell exits the second gap, the cell will now
proceed to meiosis I. Prophase I is the most complex
phase of meiosis and typically occupies over 90
percent of the time required for meiotic cell division.
It has been subdivided into five substages: leptonema,
zygonema, pachynema, diplonema, and diakinesis. In
leptonema, the chromatin materials have coiled and
are already visible. In zygonema, chromosomes begin
to pair and twist with their homologues in a highly
specific manner. This pairing of chromosomes is
called synapsis. And because the pair of homologous
chromosomes, chromosomes that are exactly alike in size, location of the
centromere, and the dark – and – light banding pattern seen after staining with dyes,
8
consists of four chromatids it is referred to as bivalent tetrad. In pachynema,
crossing – over, a form of physical exchange of chromosomal region between
homologous chromosomes, takes place. In diplonema, after the crossing – over
process, the pair of homologous chromosomes begin to separate from each other and
the area of contact between two non – sister chromatids during crossing – over, called
chiasma, become more evident. In diakinesis, homologous chromosomes become
more condensed and the chiasma often terminalizes and moves down reaching the
telomeres, terminal ends of chromosomes, which delays the separation of
homologous chromosomes. In addition, the nucleus and other organelles of the cell
start to disintegrate, and the centrioles start to move toward the opposite pole of the
cell along with the radiation of mitotic spindle between them.
Prometaphase I
During prometaphase I, the nucleus and other
organelles are no longer visible. The centrioles have
reached the opposite poles of the cell. Spindle fibers
converge and attach to each bivalent tetrad from both
poles, with one homologous chromosome facing each
pole. The homologous chromosomes, which are still
held together at chiasmata, will force to move toward
the center of the cell.
Metaphase I
During metaphase I, the bivalent tetrads convene on
the metaphase plate, an imaginary plane equidistant
between the two poles of the spindle fibers.
Anaphase I
Anaphase I begins when homologous chromosomes in
each bivalent tetrad separate and pull by spindle
fibers toward the opposite poles of the cell. Along with
that action is the formation of spindle fibers between
the migrating chromosomes, which causes the cell to
elongate. In this phase of meiosis, the centromeres do
not duplicate and so, the sister chromatids (dyads)
remain attached.
9
Telophase I
The cell elongation that started in anaphase I
continues until a constriction is formed from the outer
middle portion of the cell. The dyads have reached the
opposite poles of the cell. The spindle fibers start to
disappear. Nuclei and cytoplasmic contents of the
daughter cells start to reform. The chromosomes start
to decondense.
Cytokinesis of Meiosis I
During cytokinesis, in some references is referred to
as the late telophase, the nuclei and cytoplasmic
contents of the daughter cells are fully visible. The
chromosomes are no longer visible. The constriction
continues forming the cleavage furrow, which
pinches the cell in two. Two new daughter cells are
formed, each with only one set of chromosomes
(haploid) in a replicated form.
How does the cell prepare for meiosis II while in interkinesis?
During interkinesis, the cell actively produces ATP,
RNA, and protein. The cell increases in size as well.
The duplication of cytoplasmic contents takes place.
The chromosomes uncoil to form the chromatin
materials, which will then turn into granules.
What are the phases of meiosis II?
Prophase II
As the cell exits the interkinesis, the cell will now
proceed to meiosis II. During prophase II, the
chromatin materials start to condense, forming
discrete chromosomes. The nucleus and other
organelles of the cell start to disintegrate. Centrioles
start to move toward the opposite pole of the cell along
with the radiation of spindle fibers between them.
10
Prometaphase II
During prometaphase II, chromatin materials have
coiled to form the chromosomes. The nucleus and
other organelles are no longer visible. The centrioles
have reached the opposite poles of the cell. Spindle
fibers converge and connect to the kinetochore of
chromosomes forcing them to move toward the center
of the cell.
Metaphase II
During metaphase II, the chromosomes convene on
the metaphase plate.
Anaphase II
Anaphase begins when the centromere of each
chromosome come apart, separating the sister
chromatids (monads). Spindle fibers will then pull the
monads toward the opposite poles of the cell. Along with
that action is the formation of spindle fibers between the
migrating monads which causes the cell to elongate.
Telophase II
The cell elongation that started in anaphase II
continues until a constriction is formed from the
outer middle portion of the cell. The monads have
reached the opposite poles of the cell. The spindle
fibers start to disappear. Nuclei and cytoplasmic
contents of the daughter cells start to reform. The
chromosomes start to decondense.
Cytokinesis of Meiosis II
During cytokinesis, the nuclei and cytoplasmic
contents of the daughter cells are fully visible. The
chromosomes are no longer visible. The constriction
continues forming the cleavage furrow, which pinches
the cell in two. Four new daughter cells are formed,
each with the haploid number of chromosomes.
11
What is the significant distinction between sex chromosomes and autosomes?
Why is karyotyping very important?
You have learned that chromosomes come in
homologous pairs. Such pairing of chromosomes with
their homologues can be readily described in a
karyotype, an ordered display of magnified images of
an individual’s chromosomes arranged in pairs,
starting with the longest. A karyotype shows the
chromosomes condensed and doubled, as they appear
in the metaphase stage of cell division. The 22 pairs of
chromosomes are called body chromosomes, also
called autosomes. The last pair of chromosomes are
the sex chromosomes which determine the gender of
an organism.
Thought – Provoking Question 1: How would the karyotype of a human female
differ from the male karyotype?
Humans and other mammals have two sex chromosomes – X chromosome and Y
chromosome. These two distinct sex chromosomes are an important exception to
the general pattern of homologous chromosomes.
Two X chromosomes (XX) are found in every female individual and male individuals
have distinct X and Y chromosomes (XY). Only small parts of the X and Y
chromosomes are homologous; most of the genes carried on the X chromosome do
not have counterparts on the tiny Y, and the Y chromosome has genetic features
missing on the X.
During meiosis, segregation of sex chromosomes and autosomes happen and
because females have two X chromosomes, meiotic cell division distributes only one
X chromosomes in each haploid egg cell. In males, half of the sperm carries a Y
chromosome and half carry an X chromosome.
Thought – Provoking Question 2: Which gamete determines the sex of the
offspring? Why?
12
Why is the occurrence of mutations in meiotic cell division often more fatal to
an organism than the occurrence of mutations in mitotic cell division? How
can non - disjunctions lead to chromosomal variations and abnormalities in the
daughter cells produced through the process of meiosis?
To grow and develop normally, an individual must
have a complete set of chromosomes. An abnormal
condition, or death at an early or later age, results
when there is a change in structure or number of
chromosomes. A change in number usually results
from the abnormal separation of chromosomes during
cell division.
You will recall that
chromosomes normally
move away from each
other to opposite poles during meiosis. But
sometimes, they do move to the same pole, resulting
in a new cell, sex cell in particular, that contains an
extra chromosome or an absence of a chromosome.
Fertilization of these abnormal sex cells results in
offspring with chromosomal abnormalities.
Abnormalities involving the presence of an extra
chromosome or the absence of a chromosome are
called aneuploidies. Aneuploidy is caused by non –
disjunction, the failure of chromosomes to correctly
separate as homologues during meiosis I or sister
chromatids during meiosis II. An individual with an
extra chromosome – with three of one kind – is said
to be trisomic for that kind of cell. An individual
lacking one member of a pair of chromosomes is said
to be monosomic.
When disease causes multiple symptoms, we refer to
it as a syndrome. Virtually all chromosomal
abnormalities fall into this category. In general,
chromosomal abnormalities involving the autosomes
have devastating consequences. To know more about
the
different
genetic
conditions
involving
chromosomal abnormalities, the table on the next
page is provided for you.
13
Chromosomal
aberrations
Monosomy
Turner’s syndrome
Trisomy
Down’s syndrome
Errors in Meiosis
Error in the structure or
number of chromosomes
Characteristic properties
Has only one X
chromosomes in the 23rd
pair
The affected individual is
female, short, with webbing of
the neck, has a low hairline on
the back of the neck, has a
broad chest, exhibits slight
mental deficiency, and the
breasts, the external genital
organ, and secondary
characteristics do not develop
Has an extra copy of
chromosome in the 21st
pair
The mouth is usually open,
slanting eyes, upper eyelid
appears bulging or swollen,
usually a low nose bridge, low –
set ears, short broad hands
with abnormal palm prints,
mentally retarded, with heart
and respiratory ailments, and a
reduced life expectancy.
The jaws are small, clenched
fingers, harelips, cleft palates,
malformations of the heart,
skull, face, and feet, severely
mentally retarded, and die at
three to four months of age.
There is deformation of hands
and feet, as well as a face
severely deformed by a cleft lip
and cleft palate, and live from
about a few days to a few
months.
The affected individual is male,
has a general male appearance,
the testes are usually small,
sperm cells are usually not
produced, most are mentally
handicapped, the arms are
longer than average, the breasts
are slightly developed, the voice
has a higher pitch than in
normal males.
Edward’s syndrome
Has an extra copy of
chromosome in the 18th
pair
Patau’s syndrome
Has an extra copy of
chromosome in the 13th
pair
Klinefelter’s
syndrome
Has an extra copy of X
chromosome and one Y
chromosome in the 23rd
pair
14
Metafemale or
Triple X syndrome
Has three to four X
chromosomes in the 23rd
pair
The affected individual is
female, does not have distinct
clinical features but may have
menstrual irregularities,
secondary amenorrhea, and
premature menopause,
generally has subnormal
mental abilities.
Metamales or
Has an extra copy of Y
The affected individual is male,
Double Y syndrome chromosome and one X
tall, with low IQ, with severe
chromosome in the 23rd
facial acne during adolescence,
pair
severely mentally retarded.
Deletion refers to the loss of a fragment of a chromosome
Cri – du – chat or
Deletion of a segment of a
The affected individual has a
th
cat – cry syndrome
chromosome in the 5
characteristic high – pitched cry
pair
during infancy similar to a
kitten in distress, malformed
head and face, severely
mentally retarded, with low IQ,
and malformed and improperly
functioning brain, heart, eyes,
kidneys, bones, and larynx.
William’s syndrome Deletion of a segment of a
The affected individual has
th
chromosome in the 7
broad forehead, flat nasal
pair
bridge, lower eyelid appears
bulging or swollen, full lips,
wide mouth, very active, and
with cognitive impairment and
developmental delays.
Thought – Provoking Question 3: Why is the occurrence of non - disjunction in
meiosis often more detrimental to an organism than the occurrence of non disjunction in mitosis?
15
What’s More
Since you have learned already the two ways that cells of eukaryotic organisms
divide, the activity below is provided for you. All you have to do is to complete the
following table to compare mitosis and meiosis.
Comparative Analysis of Mitosis and Meiosis
Bases of comparison
Mitosis
Number of chromosomal duplications
Number of cell divisions
Number of daughter cells produced
Number of chromosomes in daughter cells
How chromosomes line up during
metaphase
Genetic relationship of daughter cells to
parent cell
Functions performed in the human body
Meiosis
Thought – Provoking Question 4: What other similarities and differences do you
think between mitosis and meiosis?
16
What I Have Learned
Now it’s your turn! Read and fill out the “I have learned oath” below.
Exploring the mechanisms of cell cycle and meiosis is an astonishing learning
experience. I can now understand how my sex cells were formed and as to how some
of the traits of my parents were properly segregated to enhance phenotypically my
appearance.
I have learned from this module that meiosis, like mitosis, is preceded by the
duplication of genetic materials which happens in (1)__________. The significant
difference between mitosis and meiosis is that in meiosis, the cell divides
(2)__________ to form (3)__________ genetically unique daughter cells. The first meiotic
division, (4) __________, starts with the condensation of duplicated genetic materials
forming darkly – staining finite bodies called (5)__________ followed by the pairing of
these condensed bodies known as (6)__________. They were paired up based on their
(7)__________. Each homologous pair is known as (8)__________ because the pair itself
is composed of four sister chromatids. The process of pairing is followed by the
blending of genetic materials for each homologous pair. This process is called
(9)__________ and due to this process, you inherit some of the traits coming from your
parents. After this process, the homologous pair is now ready to line up at the center
of the cell which takes place in (10)__________ followed by the segregation of sister
chromatids in the form of (11)__________ which happens in (12)__________. This
segregation process will reduce the chromosome number of cell to (13)__________ of
its original because each set of chromosomes has already been distributed in each
of the soon – to – be – daughter cells. At the end of first meiotic division, (14)__________
are produced, each with the (15)__________ set of chromosomes.
I have also remembered that the second division of meiosis, (16)__________, and
mitosis are essentially the same. The significant difference is that the second meiotic
division starts with (17)__________ and the genetic materials of each cell do not
undergo duplication. The second meiotic division starts with the condensation of
genetic materials which occurs in (18)__________. As the condensation of genetic
materials has reached its completion to form chromosomes, the chromosomes are
now ready to line up at the center of the cell which takes place in (19)__________
followed by the separation of sister chromatids in the form of (20)__________ in
(21)__________. At the end second meiotic division, (22)__________ are formed, each
with the (23)__________ set of chromosomes.
17
Isn’t it amazing? That my body and my traits were a result of this incomparable
process. And what’s more amazing is how the sex cells genetically plan the blueprint
of life for future progenies and generations. Scientists and field experts collaborate
to make a consensus body of knowledge just to explain this astonishing experience
of sex cells. I ___________________ (write/state your name), do solemnly pledge that I
will only do good and responsible science for my society specifically in learning about
cell cycle and meiosis.
18
What I Can Do
Biology indeed offered us great adventures as we learn greatly about life! It
teaches us to know how the traits were passed from parents to offspring. Also, it
helps us to realize that we are products of a very small biomolecule which is
scientifically known as deoxyribonucleic acid (DNA). This minute biomolecule serves
as the language for genetic interpretation and we exist on what we are and what we
should look like because of the codes printed in our DNA.
Due to the advent of modern technology, our knowledge about DNA goes
beyond from what we know about it before. Scientists and field experts can now enter
and modify the codes printed in our DNA. Does it sound like magic? It’s not magic,
it’s science! They can now manipulate the traits to produce new traits and expected
traits. Science indeed did not stop surprising us.
We live in a world where some fictions from sci – fi movies could possibly
become science. An example of this is a scientific study made by some physicians,
geneticists, and embryologists from United States, Japan, and Europe. Because of
their studies about preimplantation genetic diagnosis and gene – altering
technologies, you can now learn, as you become a parent, your child’s sex and
discover the traits they inherited and possessed as they grow up. Also, you can now
choose your children’s traits instead of leaving those traits in nature. Because of
these studies, physicians can now routinely test embryos of different donors for
hundreds of genes and use these embryos for soon – to – be – parents and child –
bearing – want – to – be – parents to pick embryos with genes that inhibit diseases
or to pick the sex of their future progeny.
So far so good, right? But behind these good benefits, the controversy is
swirling around gene – altering techniques that poses ethical and social dilemmas
that more and more people are now facing. And for all the issues surrounding gene
editing techniques, these scientific developments of modifying humankind should
prompt us to realize that science is no longer a thing that we know in the past or a
fictional stuff of the future. It is a reality that we must all now face.
In your point of view as a senior high school STEM student, should gene
editing be performed on human embryos? Is micromanipulation of gametes and
embryos helpful or can make a permanent change to society? Explain your answer
using the concepts that you have learned from this module.
19
Assessment
Let’s see how well you have enjoyed the amazing world of cell cycle and mitosis by
answering the following questions. Choose and encircle the letter of the best answer.
_____1. How are DNA, genes, and chromosomes related?
a. DNA is a long strand of genetic code where the chromosome is found. This
long strand is subdivided into many segments which are called as genes.
b. DNA is a long strand of genetic code found inside the chromosome. This long
strand is subdivided into many segments which are called as genes.
c. DNA is a strand found in our gene. This gene is where the chromosomes are
formed.
d. Chromosomes are darkly – staining bodies and they are found inside the
gene which controls a particular DNA code for a trait.
_____2. What part of meiotic division is similar to mitosis?
a. Meiosis I
c. Interkinesis
b. Reduction division
d. Meiosis II
_____3. What is the significance of “crossing over”?
a. Makes the DNA more durable
b. Contributes to genetic diversity
c. Makes the cycle easier to perform
d. No significance, only occurs due to proximity
_____4. A biologist prepares a slide of stained cells undergoing mitotic prometaphase
for examination under a light microscope. He sees a number of very dark
stained rod – shaped structures in the cells. These “colored bodies” are most
likely ____.
a. Mitochondria
c. Chromosomes
b. Ribosomes
d. Microtubules
_____5. A fruit fly somatic cell contains 8 chromosomes. This means that _____.
a. 4 identical chromosomes are possible in its gametes
b. 8 identical chromosomes are possible in its gametes
c. 4 distinct chromosomes are possible in its gametes
d. 8 distinct chromosomes are possible in its gametes
_____6. At metaphase I, homologous chromosomes are connected only at what
structures?
a. Chiasmata
c. Microtubules
b. Recombination nodules
d. Kinetochores
20
_____7. What phase of mitotic interphase is missing from meiotic interkinesis?
a. G0 phase
c. S phase
b. G1 phase
d. G2 phase
_____8. In which phase of meiosis would certain gene segments of the homologous
pairs of chromosomes “cross – over” and exchange genetic information?
a. Prophase I
c. Prophase II
b. Metaphase I
d. Metaphase II
_____9. Which event takes place during anaphase II of meiosis?
a. Nuclear membrane breaks down.
c. Sister chromatids separate.
b. Spindle fibers break down.
d. Cytoplasm divides.
_____10. If someone only has one X chromosome and no Y chromosomes, they _____.
a. are metafemales
c. have Klinefelter’s syndrome
b. have Turner’s syndrome
d. are metamales
_____11. The chromosomal abnormality that causes a woman to be unusually short
in stature, have a webbed neck, and generally lack feminine secondary
sexual characteristics is _____.
a. Triple X syndrome
c. XYY syndrome
b. Turner’s syndrome
d. William’s syndrome
_____12. The chromosomal abnormality that causes a man to have asexual to
feminine body contours with large breasts; small penis, testes, and prostate
gland; relatively little body hair; and sterility is _____.
a. Klinefelter’s syndrome
c. Down’s syndrome
b. XYY syndrome
d. Jacob’s syndrome
_____13. If a segment of a chromosome is lost, it is called _____.
a. an inversion
c. a deletion
b. a translocation
d. a duplication
_____14. Triple X individuals _____.
a. are sterile
b. lack developed breast
c. may have menstrual irregularities
d. have severe facial acne
_____15. Any deviation in the number of chromosomes that involves individual
chromosomes, as opposed to entire sets of chromosomes, is known as
which one of the following?
a. Aneuploidy
c. Duplication
b. Disomy
d. Translocation
21
Additional Activities
I know! You can’t get enough of the incomparable scientific adventure of cell cycle
and meiosis. Don’t worry, you won’t miss out with the following additional exciting
mind and hand activity!
Imagine a future where, if you were not capable of producing sex cells but you wanted
to have a child that is genetically yours, doctors will simply create sex cells from your
body cells like skin cells, liver cells, or brain cells. Imagine a future where your
somatic cells can be modified into egg cells and sperm cells for you to have a child
that is literally from your own flesh and blood. As morbid as this may sound, you
won’t even have to wait around for someone to have a miserable life just because
they don’t have the capability to have a child.
This is the promise held out by cell modification research, a highly controversial field in
reproductive technologies. If – and this is the big IF – cell modification research delivers
on this promise, a wide range of medical advancements can be developed to help millions
of couples to have a child. The feasibility of such a revolutionizing technique of
transforming our flesh has been recognized for 11 years. This scientific study was first
beheld by some physicians, geneticists and embryologists from Japan and United States.
Because of their studies about cell modification, you can now make a child by just
scraping a portion of your skin and modifying it into sex cells ready for an incomparable
fertilization. Also, through cell modification, couples have now the means of providing
sex cells not only for themselves but also for those who lack them. Lastly, instead of
undergoing painful egg – production and extraction procedures involving large doses of
hormones with fluctuating long – term effects, a woman can now have a limitless supply
of egg cells made from a strand of hair.
Cell modification research is a testament to man’s creative mind to push the
boundaries of science. Through this study, we now know that we have a limitless
source of cells that can be fashioned to become sex cells. But behind the good
benefits cell modification research has given to us, the controversy is swirling around
this extraordinary technique. And for all the issues surrounding cell modification
techniques, this scientific development should prompt us to realize that science can
stretch out the potentials of humankind and scientific evolution will continue to
grow. It is a reality that we must all now face.
For your task: Make an editorial cartoon (with a title) showing your perspective for
artificial sex cells that will answer to the following questions: What do you think are
the most serious ethical issues that must be dealt with before these cell modification
techniques are used on a wide scale? Why do you think these issues are significant?
Your product will be assessed based on the following criteria: organization and
content accuracy, appropriateness of elements, creativity, and appearance. The
actual rubric to be used in assessing your product will be found on page 21.
22
Criteria
Organization and
Content
Accuracy
(_____/12)
Rubric
Exceeds (12)
All ideas are
easily
distinguishable
and accurately
detailed.
Appropriateness
of Elements
(_____/12)
Appropriate
materials were
selected and
creatively
modified in
ways that made
them better.
Creativity
(_____/12)
The product is
very creative
and eye
catching. Great
use of colors,
texture, and
shapes.
Appearance
(_____/12)
Great care
taken in
construction
process so that
the structure is
neat, attractive,
and accurate.
for Editorial Cartooning
Good (9)
Fair (6)
Most of the
Most of the
ideas are
ideas are not
distinguishable distinguishable
and accurately
and more
detailed.
details are
needed in order
for them to
identify.
Appropriate
Appropriate
materials were
materials were
selected and
selected
there was an
attempt at
creative
modification to
make them
better.
The product is
The product is
creative. Lots of somewhat
colors, shapes,
creative. Not
and appealing
very appealing.
design are
Limited use of
used.
creative
materials.
Limited used of
colors, shapes,
and appealing
design.
Construction
Construction is
was careful and accurate, but 3
accurate for the – 4 details
most part but 1 could have
– 2 details
been refined for
could have
a more
been refined for accurate
a more
product.
attractive
product.
Total: _____ + 2 =
_____/50
23
Poor (3)
The ideas are not
detailed, they look
like uniformed
and/or misshapen
making them
indistinguishable.
Inappropriate
materials were
selected and
contributed to the
product that
performed poorly.
The product lacks
creativity and
looks messy.
Lacks colors,
shapes, and
appealing design
Construction
appears careless.
Many details need
refinement for a
strong or attractive
product.
Additional Activities:
Students’ answers
may vary.
24
Assessment:
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
15.
B
D
B
C
C
A
C
A
C
B
B
A
C
C
A
What’s New
What I Can Do:
Students’ answers
may vary.
Organism
Amoeba
Chimpanzee
Earthworm
Fern
Hamster
Honeybee
Human
Onion
n
25
24
18
505
22
16
23
8
2n
50
48
36
1010
44
32
46
16
What I have Learned:
1.
2.
3.
4.
5.
6.
7.
8.
What’s More:
interphase
metaphase II
twice
four
meiosis I
daughter cells
chromosomes
synapsis
homologues
bivalent tetrad
What is It:
Students’ answer
may vary.
10. metaphase I
11. dyads
12. anaphase I
13. half
19.
20. monads
21. anaphase II
22.
four
14. two daughter cells 23. haploid
15. haploid
16. meiosis II
17. haploid cells
What’s In:
What I Know:
Students’ answer
may vary.
What is the difference
between autosomes
and sex chromosomes?
Why is karyotyping very
important?
Students’ answer may
vary.
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
15.
Why is the occurrence
of mutations in meiosis
often more detrimental
to an organism than the
occurrence of
mutations in mitosis?
How can non disjunctions lead to
chromosomal variations
and abnormalities in the
daughter cells
produced through the
H
I
G
J
F
K
E
L
D
M
C
N
B
O
A
Answer Key
References
Belardo, Gisselle Millete M., et al. (2016). General Biology 1. Quezon City, Philippines:
Vibal Group, Inc. Pp. 104 – 139.
Calsado, Chuckie Fer, et al. (2016). Teaching Guide for Senior High School: General
Biology 1. Quezon City, Philippines: Commission on Higher Education.
Pp. 36 – 44.
Campbell, Neil A., et al. (2009). Biology: Concepts and Connections. Sixth Edition.
Jurong, Singapore: Pearson Education Asia Pte Ltd. Pp. 125 - 151.
Capco, Carmelita M., et al. (2000). Biology. Second Edition. Quezon City, Philippines:
Phoenix Publishing House, Inc. Pp. 231 – 239.
Hadsall, Annalee S., et al. (2008). Exploring Science and Technology: Biology. Makati
City, Philippines: DIWA Scholastic Press, Inc. Pp. 251 – 259.
Strauss, Eric, et al. (2003). Biology: The Web of Life. Second Edition. Jurong,
Singapore: Pearson Education Asia Pte Ltd. Pp. 102 – 123.
25
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Department of Education – Region III,
Schools Division of Bataan - Curriculum Implementation Division
Learning Resources Management and Development Section (LRMDS)
Provincial Capitol Compound, Balanga City, Bataan
Telefax: (047) 237-2102
Email Address: bataan@deped.gov.ph