RIZAL TECHNOLOGICAL UNIVERSITY
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SESSION NO. / WEEK NO. 3
MODULE NO. 2: THE SCIENTIFIC SELF
1. Mechanisms of Reproduction
2. Heredity and Behavior
3. Factors affecting an unborn child
4. Chromosomal abnormalities
Overview
This module will talk about the biological component of the self, and it
will start with the concept of reproduction. It will also cover how heredity sets
in and how it affects the person. You will gain scientific knowledge about
determining sex and the different factors that may affect the child. You will
know more about how one’s biological component will shape one’s behavior
while considering the environment.
This part of the self is scientific in nature and it is essential for you to
understand how it started and what happens as the person grow older.
Study Guide
● You can complete this module at your own phase. It means you
can take every part to study depending on your capability to do
so.
● This module starts with a brief overview about what the topic is
all about. It will also tell you the learning outcomes we would
want you to accomplish after completing this module. The
presentation of topic has complete resources you can check for
further readings and clarifications.
● Requirements involve learning activities and assessment which
are available on the last part of the module. Take time to study
each lesson carefully to apply these new learnings
appropriately.
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Learning Outcomes
1.
2.
3.
4.
Discover and understand the process of reproduction;
Explain the mechanics of heredity, and how it affects the self;
Have a basic knowledge on factors that may affect the unborn child;
Be aware on the scientific explanations on the developmental abnormalities.
Topic Presentation
It is normal for you to get curious where you came from. It is natural to
ask questions and be curious about how everything started. To attain an
understanding about such, it is important that you look at it through the
scientific lens—science of heredity. This will open the door for you to
understand more about how each one of us started our journey in the world.
THE MECHANISM OF REPRODUCTION
The beginning of human life starts with the union of two cells inside a
woman’s body. In your biology class, we had an introduction regarding the
reproductive system of both males and females. Male’s reproductive system
produces sperm cells during an intercourse and the female reproductive
system produces an egg cell every month.
During an intercourse, a man ejaculates and releases semen to a woman’s
vagina. In such ejaculation, there are around 150 million sperm cells released.
The sperm cells travel across the vagina up to the fallopian tube where the
egg cell awaits. Unfortunately, the journey is not easy for them. Around 85%
of these sperm cells are not ‘strong enough’ to travel. This leaves only
around 15% of these sperm cells capable to reach the right fallopian tube
where the egg resides. They have 12-48 hours to do this or else, they will die.
The uterus lining gets thicker every month to prepare the woman’s body for a
fertilized egg. The inner lining of the womb called endometrium prepares it. It
thickens with different layers on it. There are networks of blood vessels you
can see here. The endometrium acts as a support system as the baby grows
larger in the mother’s womb. These tissues serve as a defense system too for
the mother’s body as the embryo pushes itself more and more in the process
of pregnancy. However, when the egg is not fertilized, the endometrium with
its blood vessels falls off and that causes the menstruation.
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The womb lining, or endometrium, at its thickest (Credit: Steve Gschmeissner/SPL)
When the two unites, the fertilized egg is called a zygote. This egg has a total
of 46 chromosomes with equal number of chromosomes from each parent. 23
came from the mother and 23 came from the father. The chromosomes
contain chemical packets called as genes which carries the hereditary traits.
Approximately 3 days after fertilization, a 16-cell conceptus reaches the
uterus. The cells that had been loosely grouped are now compacted and look
more like a solid mass. The name given to this structure is
the morula (morula = “little mulberry”). Once inside the uterus, the conceptus
floats freely for several more days. It continues to divide, creating a ball of
approximately 100 cells, and consuming nutritive endometrial secretions
called uterine milk while the uterine lining thickens.
At this developmental stage, the conceptus is referred to as a blastocyst.
Within this structure, a group of cells forms into an inner cell mass, which is
fated to become the embryo. The cells that form the outer shell are
called trophoblasts. These cells will develop into the amniotic sac and the
fetal portion of the placenta that will provide nutrients to the unborn baby.
CELL DIVISION
During cell division, the cell undergoes two major stages called mitosis and
meiosis. In mitosis, the cell divides by duplicating Deoxyribonucleic acid
(DNA). It leads to the formation of new cells each of which has 23 pairs of
chromosomes. You started from a single embryonic cell and were
continuously growing through mitosis. Even after you were born, mitosis
continues its functions. It replaces cells through everyday hassles. The
constant replenishment of your skin comes from mitosis and it occurs all
throughout your body, keeping everything in order.
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In meiosis, it rearranges the
genetic deck, generating cells
that are distinct from one
another and from the original
parent cell. These cells are
called gametes and they are
usually used when pertaining to
egg and sperm cells.
Your body can undergo mitosis
but meiosis only occurs in cells
that will become either eggs or
sperm. Therefore, mitosis is for
growth and maintenance, while
meiosis
is
for
sexual
reproduction.
PREGNANCY MONTH BY MONTH
Once conception took place, your body will undergo cell division and will go
through the following process as part of pregnancy.
First month
After the egg has been fertilized
by the sperm, it starts to divide
into more cells. This happens all
the time it is carried along the
fallopian tube to the uterus. By
the time it reaches the uterus the
fertilized egg has become a
cluster of cells which float in the
uterine cavity until it embeds in
the wall of the uterus. This
implantation in the wall of the
uterus is when conception is
complete. This is roughly 4 weeks
after day one of the last
menstrual period if you have a
28-day cycle.
Second month
At 5 weeks the embryo is the size of a grain of rice (about 2 mm long) and
would be visible to the naked eye. It has the beginnings of a brain with 2 lobes
and its spinal cord is starting to form.
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At 6 weeks of ‘pregnancy’ (3-4
weeks after fertilization) the
embryo has a head with simple
eyes and ears. Its heart has 2
chambers and is beating. Small
buds are present that will form
arms and legs later. The
beginnings of the spine can be
seen and the lower part of the
body looks like a tail.
At 7 weeks, the limb buds have
grown into arms and legs. Nostrils
can be seen on the embryo’s
face. The heart now has 4
chambers.
At 8 weeks, the eyes and ears are growing, and your baby is about 2 cm long
from crown to rump. The head is out of proportion with the body and the face
is developing. The brain and the blood vessels in the head can be seen
through the thin skin. The bones in the arms and legs start to harden and
elbows and knees become apparent. Fingers and toes can also be seen.
Third month
What is known as the embryonic period finishes at the end of week 8 and the
fetal period begins. This period sees rapid growth of the fetus, and the further
development of the organs and tissues that were formed in the embryonic
period.
At week 9 the head is almost half
the crown to rump length of the
fetus. Then the body grows
substantially in length until by
week 12, the head is more in
proportion. By the time you are
12 weeks’ pregnant, your baby is
just over 5 cm long from crown to
rump.
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Its body is fully formed, including ears, toes and fingers complete with
fingernails. The external genitals appeared in week 9, and now, by week 12,
have fully differentiated into male or female genitals. By week 12 the eyes
have moved to the front of the face and the eyelids remain closed together.
Fourth month
Your baby may suck its thumb now. By 14 weeks your baby will be about 9-10
cm long. Its body is now covered with a layer of fine hair called lanugo. By 16
weeks its face is becoming more
human in appearance, although the
chin is small and the mouth is quite
wide. Between 16 and 24 weeks you
should feel your baby move for the
first time — it may at first feel like
butterflies.
Fifth month
The rapid growth that your baby has
been experiencing now begins to
slow a little. By week 20 your baby
measures about 18 centimeters
from crown to rump and is half as
long as it will be when born. The
legs are now in proportion with the
body and the fingernails are well developed. Faint eyebrows are visible. At
this stage, you will feel your baby moving about a lot, often when you lie
down.
Sixth month
By 24 weeks your baby’s organs are fully formed. The baby now has the face
of a newborn baby, although the eyes are rather prominent because fat pads
are yet to build up in the baby’s cheeks. The eyelids are fused until weeks 25
to 26 when they open.
The skin is wrinkled, red and thin with little underlying fat. The skin is covered
with a waxy substance called vernix, which protects it while it is floating in the
uterus. The body is well muscled, but still thin. The baby has become better
proportioned, with the size of the body catching up with the size of the head.
Your baby’s hearing is also well developed by this stage; the baby will
respond to noise.
Seventh month
By 28 weeks lanugo hair has almost gone and hair is present on the head. Fat
is being deposited under the skin.
Eighth month
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Your baby is becoming plumper. By 30 weeks the toenails are present and by
32 weeks the fingernails have reached the ends of the fingers. The baby’s
eyes will be open when the baby’s awake.
By about 32 weeks the baby will have settled into a downward position as
there is no longer enough room left in the womb for it to move about freely.
You will feel occasional vigorous jabs of
the baby’s arms and legs.
If your baby is a boy, his testes will
migrate down into the scrotum in the 8th
month.
Ninth month
Sometime between 36 and 40 weeks,
the baby’s head will engage — that is,
the head will be lying just on top of your
cervix.
The lanugo hair that had covered your
baby has now mostly disappeared,
although some hair may remain low on
the forehead, in front of the ears and down the center of the back. The
toenails should have reached the tips of the toes.
Full term
By full-term, your baby should weigh about 2.7 to 3.5 kg, although full-term
babies can weigh anything from 2.5 to 5 kg, and measure 35 to 38
centimeters from crown to rump and 44 to 55 cm from the baby’s head to its
toes. These are just average figures, though, and there can be wide variation
in the measurements. So now, 38 weeks after conception, your baby has all
its organs and body systems ready for the big moment when it is born into the
world.
Source: https://www.mydr.com.au/babies-pregnancy/baby-s-development-in-thewomb
You may also watch: https://topdocumentaryfilms.com/national-geographic-in-thewomb/
SEX DETERMINATION
A normal female has XX sex cells while a normal male has XY sex cells. The
combination of XX chromosomes from both parents will result to a baby girl.
On the other hand, a pairing of XY chromosome will result to a baby boy.
MULTIPLE BIRTHS
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There are instances where a person gives birth not only to one but to two or
more child. A woman can bear two children at the same time and they are
called as twins. There are two major types of twins: Identical and Fraternal
twins.
Identical twins or monozygotic twins came from a single egg fertilized by a
single sperm cell. At some point in its fertilization process, the egg splits into
two—causing the formation of two separate identical babies. Since they came
from the same egg cell, they are mostly identical in appearance.
On the other hand, Fraternal twins came from two separate egg cells
fertilized at the same time. This will lead to the differences in the appearance,
gender, and characteristics. It is important to note that even twins are
identical, environmental influences set in which can cause differences in their
characteristics.
Occurrence of multiple births vary across the human race. It is common
among African descent and less common among European descent, and the
least common among Asians. It recurs to those families with a history of
multiple births in their generation and older mothers that are up to 40 years
old.
Source: https://www.britannica.com/science/multiple-birth#/media/1/397093/136814
HEREDITY AND BEHAVIOR
We are aware that every person has both the nature and nurture aspects to
consider when talking about behavior. For this module, the focus will be on
the nature process—heredity.
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The idea of heredity came from Gregor Mendel who published his work on
pea plants in 1865. Unfortunately, his work is not widely known at that period
and was only rediscovered around 1901. Before, people assume that
Mendel’s work only accounts the big qualitative differences and the idea of
quantitative genes is not considered. It was until Ronald Aylmer Fisher
created a paper using Mendel’s pioneer study that paved the way for
scientists to realize that traits can be inherited.
Heredity is defined as the transmission of genetic traits or
characteristics from parents up to the third line of ancestry. It begins from
the moment of conception and within one’s chromosomes, genes carry traits
that are manifested by an individual.
Traits can be dominant or recessive. Dominant traits are those that are
observable while recessive traits are expressed less. Each of us receives a
pair of each trait and each of these traits can be dominant or recessive. You
can observe a dominant trait easily because it is reflected on the child’s
overall being. If a child inherits both recessive traits from the parents, it is the
only time that these recessive traits can be displayed. Knowing which other
traits you have inherited from your parents will unravel during your
development.
Here are examples of dominant and recessive traits:
NATURE AND NURTURE
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It is always a debated topic as to how much amount of inherited
characteristics affect one’s behavior. It is still unresolved as of this moment
but as what the interplay of both nature and nurture suggests, nature—one’s
biological component, affects a person’s behavior.
Researchers in behavioral genetics study the way in which genetic factors
affect behavioral traits. Using family studies, they investigated whether
occurrence of mental illness within family members and relatives occur as
they share similar genetic makeup. In twin studies, they compare both
identical and fraternal twins to assess which traits they possess are affected
by genetics. There are cases where they separate twins and let them grow up
from different environments to assess differences or similarities amidst
environmental differences. It prompts researchers to investigate more on how
environment affects traits rather than heredity itself.
FACTORS AFFECTING AN UNBORN CHILD
The mother must be healthy to carry out the pregnancy. However, there are
certain factors that affect an unborn child amidst this pregnancy that they
must watch out.
Mother’s Existing Health Condition
● High Blood Pressure- Uncontrolled blood pressure can result to damage
in the mother’s kidney and increase the risk for low birth weight or
preeclampsia. It is important to have the blood pressure checked at every
checkup for the doctor to provide necessary interventions before the birth
delivery.
● Polycystic Ovary Syndrome (PCOS) - Women with this condition have
higher rates of pregnancy loss before 20 weeks of their pregnancy.
● Diabetes- It is important that pregnant women are mindful of their sugar
intake if they have diabetes. During the first weeks of pregnancy, high
blood sugar levels can cause birth defects. Even those with diabetes
under control can experience changes in her metabolism that require
extra care. Babies whose mother have high blood sugar tends to be
bigger but low blood sugar upon birth. That is the reason why it is
important to control blood sugar during pregnancy.
Age
Teenage pregnancy can most likely develop pregnancy-related high blood
pressure and anemia. Some of them go through preterm labor and delivery
than those who were older. First time pregnancy over 35 years old on the
other hand have normal pregnancies however, older women have higher risk
for pregnancy concerns than younger ones. These include hypertension,
diabetes, pregnancy loss, ectopic pregnancy, excessive bleeding, prolonged
labor, and caesarian delivery.
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Lifestyle
Pregnant women should be mindful of their lifestyle. A pregnant woman must
take care of her body and what she takes in. Being healthy on this period
matters a lot for the baby’s health. However, some are not mindful about what
they take into their bodies such as alcohol, tobacco, and drugs.
● Alcohol- Drinking alcohol during pregnancy can increase baby’s risk
for Fetal Alcohol Spectrum Disorders (FASDs), sudden infant death
syndrome, and other related problems. FASDs have a variety of effect
to the child such as intellectual and developmental defects, behavioral
problems, abnormal facial features, and organ disorders.
https://www.healthychildren.org/SiteCollectionImagesArticleImages/FASD_Slide1_600x305.jpg
● Tobacco- Smoking during pregnancy puts the fetus at risk for preterm
birth, certain birth defects, and sudden infant death syndrome (SIDS).
One study showed that smoking doubled or even tripled the risk
of stillbirth, or fetal death after 20 weeks of pregnancy.
● Drug use- Research shows that smoking marijuana and taking drugs
during pregnancy can also harm the fetus and affect infant health. One
study showed that smoking marijuana and using illegal drugs doubled
the risk of stillbirth. Smoking marijuana during pregnancy can interfere
with normal brain development in the fetus, possibly causing long-term
problems.
Uterine blood flow
A pregnant woman experiencing an abnormal uterine blood flow has high
risk for eclampsia. This is a threatening complication that can endanger
the life of the expectant mother that can cause seizures or coma.
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CHROMOSOMAL ABNORMALITIES
Every cell in our body is composed of 23 pairs of chromosomes—a total of 46
chromosomes from both parents. The first 22 pairs are called autosomes
while the 23rd pair consists the sex chromosomes, X and Y. Females have
both X and X chromosomes while males have X and Y chromosomes. All the
information your body needs to grow and develop came from your
chromosomes. Each of these chromosomes contain thousands of genes,
which makes proteins that direct our body’s development and growth.
However, there are instances that chromosomal abnormalities occur. Such
abnormality occurs when a chromosome goes missing, switch pairing, or
there are added chromosomes from the usual count. This will result to birth
defects that can affect the brain and other parts of the body. These changes
in the chromosomes called as mutation is fatal to the embryo and at the same
time, can lead to the development of diseases.
There are different types of chromosomal abnormalities and it is important to
note that they can be categorized as numerical or structural.
Numerical abnormalities refer to the incident where a whole chromosome is
either missing from or added to the normal pair.
Structural abnormalities refer to the incident where a part of an individual’s
chromosome is missing, added, or switched to another chromosome.
These chromosomal abnormalities take place when there is an accident
during the formation of the zygote or as the cell division continues in the
development stages of the baby. The age of the mother and certain factors
may contribute in the occurrence of these genetic errors. These can cause
defects to the child depending on the specification of abnormality acquired.
Some chromosomal abnormalities lead to miscarriage, diseases, or problems
in growth and development.
Structural abnormalities came from breakage and incorrect rejoining of
chromosomal segments. These abnormalities cause the diseases. The
structural rearrangements can only be considered balance if the chromosomal
set is still present though they are rearranged. However, it can be considered
unbalanced if information is missing or added. Unbalanced arrangements
include deletions, duplications, or insertions in a chromosomal segment.
TYPES OF CHROMOSOMAL ABNORMALITIES
Aneuploidy- an abnormal chromosome number due to an extra or missing
chromosome. Duplication and deletion of chromosomes take place. There are
more trisomy or duplications than monosomy or single copy of a chromosome
here. The following are the most common results of aneuploidy:
1. Down’s syndrome (Trisomy 21) - a genetic condition caused by an extra
chromosome. Babies with Down syndrome however, end up with three
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chromosomes at position 21, instead of the usual pair. The disorder was first
identified in 1866 by John Langdon Down, a British physician, and later
named after him.
When a child with Trisomy 21 develops, he is at greater risk for certain
medical
problems
and
may
develop
the
following:
● Congenital heart disease
● Gastrointestinal abnormalities
● Musculoskeletal and movement
● Hearing loss
● Speech apraxia (difficulty making
problems
● Spine disorders such as scoliosis,
kyphosis or lordosis
● Endocrinologic disorders
● Epilepsy
● Sleep disorders
● Feeding disorders
● Developmental disabilities
speech sounds)
(learning disabilities, intellectual
disabilities and autism)
2. Edward’s Syndrome (Trisomy 18) - Trisomy 18 is the second most
common type of trisomy syndrome, after trisomy 21. About 1 in every 5,000
babies is born with trisomy 18, and most are female. The condition is even
more common than that, but many babies with trisomy 18 don't survive past
the second or third trimester of pregnancy.
Babies with trisomy 18 are often born very small and frail. They typically have
many serious health problems and physical defects, including:
Cleft palate
● Heart defects, including a
Clenched fists with
hole between the heart's
overlapping fingers that are
upper (atrial septal defect) or
hard to straighten
lower (ventricular septal
● Defects of
defect) chambers
the lungs, kidneys,
● Low-set ears
and stomach/intestines
● Severe developmental
● Deformed feet (called
delays
"rocker-bottom feet"
● Chest deformity
because they're shaped like
● Slowed growth
the bottom of a rocking
● Small head (microcephaly)
chair)
● Small jaw (micrognathia)
● Feeding problems
● Weak cry
3. Turner’s Syndrome- It is a condition that affects females only and results
when one of the X chromosomes is missing or partially missing. This
syndrome can cause a variety of medical problems such as short height,
failure of the ovaries to develop and heart defects.
●
●
The following signs can also be observed at birth and during infancy:
●
●
●
●
●
Wide or weblike neck
Low-set ears
Broad chest with widely spaced nipples
High, narrow roof of the mouth (palate)
Arms that turn outward at the elbows
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●
●
●
●
●
●
●
●
Fingernails and toenails that are narrow and turned upward
Swelling of the hands and feet, especially at birth
Slightly smaller than average height at birth
Slowed growth
Cardiac defects
Low hairline at the back of the head
Receding or small lower jaw
Short fingers and toes
4. Klinefelter’s Syndrome- It is a genetic condition where a boy is born with
an extra copy of the X chromosome. This affects males and is often not
diagnosed until adulthood.
It affects testicular growth which affects the quantity of testosterone produced.
It also affects muscle mass by reducing it together with facial hair, and
enlarged breast tissues.
Signs
and
symptoms
may
include:
● Low sperm count or no sperm
● Decreased facial and body
● Small testicles and penis
hair
● Low sex drive
● Less muscular compared with
● Taller than average height
other men
● Weak bones
● Enlarged breast tissue
● Increased
belly
fat
Family members should be supportive and at the same time be able to cope
with such chromosomal aberrations that the family might encounter.
Acknowledging the problem is the first step and moving forward is the next.
Making sure that you can offer support to the young ones on these crucial
times for them would mean a lot when they grew older.
Make some more research on how you can take care of someone with these
abnormalities so you can give the best care for them. More so, know more
about their condition so you know what to watch out. Get a good support
system on these times and this also includes preparing yourself financially as
there might be complications along the way. Ask the doctor about which
helping aids you might need to create a safe and healthy environment for the
kids.
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Guided Exercises / Learning Activities
Activity No. 1
The activity will be provided next week during your asynchronous classes.
References
Tomas, R. D., Sanchez, M. T., Paragas, E. T., Perez, N. S., Marasigan, J. B.,
Miranda, M. B., . . . Espiritu, A. F. (2018). Understanding The Self.
Malabon City: Mutya Publishing House, Inc.
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