Download prenatal development

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PRENATAL DEVELOPMENT
• Reproductive systems
• Stages in prenatal development
• Context of development
• Influences on prenatal development
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The Female Reproductive System
 Uterus
 A muscular chamber about
the size and shape of a pear.
 Located in a woman's abdomen,
is a hollow, elastic reproductive
organ, where a baby develops
during pregnancy.
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Female anatomy
 The uterus - is a major
female hormoneresponsive
reproductive sex organ
 Within the uterus 
fetus develops during
gestation.
 The term uterus
=womb.
 One end, the cervix,
opens into the vagina;
the other is connected
on both sides to the
Fallopian tubes.
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
Sperm is the male reproductive cell
Sperm
Chief Characteristics:
1. Tightly packed tip (acrosome) that contains 23 chromosomes
that carry genetic information
2. Short neck region
3. Trail to propel it in its search for the ovum
4. Microscopic
Fact:
 Remains capable of fertilizing egg for 24-48 hours after
ejaculation
 Of 200 million sperm that enter the vagina, only about 200
survive the journey to the fallopian tubes, where fertilization
occurs
 Males, at birth, have in their testes those cells that will
eventually produce sperm
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Ovum (Egg)

The ovum is the female reproductive cell
Chief Characteristics:
1. Round
2. .01 mm in diameter
3. Consistency of stiff jelly
4. Contributes 23 chromosomes
Fact:
 Females already have 1-2 million primal eggs at birth
 Eggs usually fertilized about 12 hours after discharged
from the ovary or they die within 12-24 hours
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ovulation
• When a young woman
reaches puberty, she
begins to ovulate
• a process in which a
mature egg cell (also
called an ovum), ready
for fertilization by a
sperm cell, is released
from one of the ovaries
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 Her body prepares for a potential pregnancy every cycle,
whether or not she want to actually conceive.
 Under the influence of Follicle Stimulating Hormone
(FSH), about 15 to 20 eggs start to mature in each ovary.
 Although it averages about two weeks, the process to
release an egg can take anywhere from about eight days
to a month or longer to complete.
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menstrual cycle
 Ovulation occurs 14 days
before the next
menstruation.
 As the average menstrual
cycle lasts 28 days
(starting with the first day
of one period and ending
with the first day of the
next menstrual period),
most women ovulate on
day 14.
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 A menstrual cycle can vary between 21 to 38 days.
 A woman is generally most fertile (able to become
pregnant) a few days before, during, and after
ovulation.
 The corpus luteum remains behind on the interior
ovarian wall, and starts releasing progesterone.
 Progesterone quickly stops the release of all other
eggs until the next cycle. The corpus luteum has a
finite lifespan, of about 12 to 16 days.
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Menstruation
 If the egg does not become fertilized as it
travels down the fallopian tube on its way
to the uterus, the endometrium (lining of
the uterus) is shed and passes through
the vagina (the passageway through
which fluid passes out of the body during
menstrual periods; also called the birth
canal), a process called menstruation.
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Pregnancy
 If the egg is fertilized by a
sperm cell as it travels down
the fallopian tube, then
pregnancy occurs, it
becomes attached to the
lining of the uterus
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 In order for conception to occur, though, there must
be three factors present:
 the egg,
 the sperm
 a medium in which the sperm can travel to reach
the fallopian tubes.
 Women produce cervical fluid under the influence
of increasing levels of estrogen in the first part of
the cycle.
 Sperms can live up to five days in fertile quality
cervical fluid
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3 Stages in prenatal development:
 Germinal stage
 Embryonic stage
 Fetal stage
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Conception: First phase of development –
Period of the zygote



The development of a single human being begins
with conception when a single sperm cell from
the male unites with an egg from a female and
forms a single cell called a zygote.
Once conception has occurred, the ovum
continues down the fallopian tube. Then, it
implants itself in the wall of its uterus.
This is the first phase of development and it is
known as the period of the zygote.
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• Business Driven• Technology Oriented • Sustainable Development• Environmental Friendly
Conception
The period of the zygote (Fertilization to 2 weeks)




This period lasts about 2 weeks.
The term zygote is used to refer to the organism throughout this
period.
In the early stages, the mass of cell is undifferentiated.
However, about four days after conception some differentiation begins,
at which point the organism is called blastocyst.
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Conception
The period of the zygote (Fertilization to 2 weeks)
• A blastocyst is a hollow ball of cells that
has developed from the fertilized egg.
• During this time, cells begin to differentiate.
• By the end of the period of the zygote, the
developing organisms has found food and
shelter in the uterus and developed into the
embryonic stage.
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Conception
The embryonic stage (2 to 8 weeks)


The second major phase of prenatal development
(the embryo) begins with completion of
implantation
It continues for another six weeks until the various
support structures are fully formed and all the major
organ systems have been laid down in at least
rudimentary form.
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Conception
The embryonic stage (2 to 8 weeks)


The embryo is especially vulnerable to interference with
healthy development.
This stage begins at week 3 and ends in the second month
(week 8) of conception.
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Conception
The embryonic stage (2 to 8 weeks)

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The embryo’s circulatory is connected to the placenta through
the umbilical cord.
The placenta is connected to both the mother’s and the
embryo’s (fetus’s) blood system, but the two systems are not
directly connected.
Small molecules pass back and forth through this large
filtering system, but large ones cannot.
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Conception
The embryonic stage (2 to 8 weeks)


So nutrients such as oxygen, proteins, sugars, and vitamins from the
maternal blood pass through to the embryo or fetus, while digestive
wastes and carbon dioxide from the infant’s blood pass back through
to the mother, whose own body can eliminate them.
The period from the ninth week of conception until the end of
pregnancy is called the fetal stage or the period of the fetus. The
embryo is called fetus when the first bone cell appears.
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Conception
• Business Driven• Technology Oriented • Sustainable Development• Environmental Friendly
The period of the fetus (8 weeks to birth)

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This is the longest prenatal period.
The seven months of the fetal stage involve primarily
a process of refining all the primitive organ systems
already in place.
At the end of the embryonic period, the main parts
exist in some basic form; the next seven month are
for the finishing process.
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Conception
• Business Driven• Technology Oriented • Sustainable Development• Environmental Friendly
The period of the fetus (8 weeks to birth)

During this phase, the organisms begins to increase rapidly in size, about
20 times its previous length; organs and body systems become more
complex.

This period is divided into second trimester and third trimester.

Table 2.1 displays milestones of prenatal development.

Figure 2.1 shows the growth of the brain during the prenatal period.
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Table 2.1 Milestones of Prenatal Development
• Business Driven• Technology Oriented • Sustainable Development• Environmental Friendly
Trimester
Period
Weeks
Length &
Weight
Major Development
1
Zygot
e
1-2
Embr
yo
3-4
¼ inch
A primitive brain and spinal cord
appear.
Heart, muscles, backbone, ribs and
digestive tract begin to develop.
5-8
1 inch;
1/7
ounce
Many external body forms and
internal organs form.
The sense of touch begins to develop,
and the embryo can move.
One-celled zygote multiplies and
forms a blastocyst.
Structures that feed and protect the
developing organism begin to form.
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Table 2.1
Milestones of Prenatal Development
• Business Driven• Technology Oriented • Sustainable Development• Environmental Friendly
Trimester
1
Period Weeks
Fetus
9-12
Length
&
Weight
Major Development
3
inches;
less
than 1
ounce
Rapid increase in size begins.
Nervous systems, organs and
muscles become organized and
connected.
New behavioral capacity such as
kicking, thumb sucking, mouth
opening and rehearsal of breathing
appear.
External genitals are well formed
& the fetus’s sex is evident.
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Table 2.1
Milestones of Prenatal Development
• Business Driven• Technology Oriented • Sustainable Development• Environmental Friendly
Trimester
Period
Weeks
Length
&
Weight
Major Development
2
Fetus
13-24
12
inches;
1.8
pounds
First fetal movement is usually felt by the
mother at about 16th weeks; bones begin to
develop; fairly complete ear is formed.
Weeks 20 - Hair growth begins; child is
very human-looking at this age and “thumb
sucking” may be seen.
Weeks 24 - Eyes are completely formed (but
closed); fingernails, sweat glands, and taste
buds are all formed; some fat deposit
beneath skin. The infant is capable of
breathing if born prematurely at this stage
but survival rate is still low for infants born
this early.
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Table 2.1• Milestones
of Prenatal Development
Business Driven• Technology Oriented • Sustainable Development• Environmental Friendly
Trimester
Period
Weeks
Length
&
Weight
Major Development
3
Fetus
25-38
20
inches;
7.5
pounds
Nervous system, blood, and breathing
systems are all well enough developed
to support life; premature born at this
stage have poor sleep/wake cycles and
irregular breathing, however.
Interconnections between individual
nerve cell (neurons) develop rapidly;
weight is added; general “finishing” of
body systems take place.
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Fertilization
• Prenatal development begins when the ovum and
sperm unite (i.e., fertilization), creating a new and
separate cell called the Zygote
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FIRST CELL DIVISION
Immediately the cell begins to duplicate, taking
approximately 30 hours to complete the first cell
division.
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BLASTOCYST
 At an increasingly faster rate, new cells are added until they form a
hollow, fluid-filled ball, called a blastocyst (about 4 or five days after
conception).
 Approximately 60 to 70 cells form the blastocyst.
 Those on the inside (called the embryonic disk) will become the new
organism whereas those on the outside will provide the protective
covering.
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IMPLANTATION
 Around the seventh or ninth day, the blastocyst implants itself into the
uterine lining.
 The protective covering quickly develops into the amnion, surrounding
the organism in amniotic fluid.
 A yolk sac also develops, producing blood cells until the liver, spleen,
and bone marrow is mature.
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EMBRYO: 5 WEEKS
8 WEEKS FROM
CONCEPTION
 The Period of the embryo lasts from about 2 weeks until about
the 8th week of pregnancy.
 During this time, the groundwork for all body structures and
organs is laid.
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Embryo: 6 Weeks
 Even before the mother knows she is pregnant:



the heart has begun to pump blood;
the muscles, backbone, and ribs have begun to appear;
and tiny buds have developed into arms, legs, fingers, and
toes.
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EMBRYO: 7 WEEKS
 By the 7th week, the liver and spleen begins producing blood
cells and the heart has developed separate chambers.
 At this time, the tiny organism shows sensitivity to touch and
freely moves about in the amniotic sac.
 However, at less than an inch long and only an ounce in weight,
the organism is still too tiny for any movements to be felt by
the mother.
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8 WEEKS
9 WEEKS
10 WEEKS
 By the end of the embryonic period, the internal organs as well as
external structures have become more distinct.
 Illustration: The development of the eyes.



"The eyes form on stems that have grown from either side of
the front of the brain out to the skin on the face
At first, the eyes are mere indentations on the side of the
head, but they develop rapidly through seven (top), eight
(middle), and 10 (bottom) weeks of pregnancy.
By three months, the eyelids form, and then close for a few
months over the newly formed eyes." (text by Your Growing
Child)
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FETUS – 3 MONTHS
 The 3rd month of pregnancy marks the end of the first trimester for the
mother, and the end of the first month of the Fetal Period.
 The fetal period is the longest prenatal period, lasting from the ninth
week to the end of pregnancy.

During the third month, the organs, muscles, and nervous system become
connected and organized.

The fetus can kick, bend its arms, make a fist, open its mouth, and can
even suck its thumb.

The skin of the fetus is thin and transparent. Thus, the internal organs
and features can still easily be seen with an internal camera
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11-14 weeks
FETUS - FOUR MONTH
 During the 4th month - vernix (a white, cheeselike substance)
covers the entire body of the fetus.
 The vernix protects the skin from chapping during the several
months that the fetus is in the amniotic fluid.
 A white, downy hair called lanugo also covers the fetus' body,
which helps the vernix stick to the skin.
 The fetus has grown large enough that the movements can
sometimes be felt by the mother. Often felt like a flutter or a
"flip-flop“. These first movements that can be felt by the mother
is called quickening.
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FETUS – 5 MONTHS
 At 22 weeks, the fetus weighs a little over 1 pound, and is about 1 foot
in length.
 At this time, the movements can clearly be felt by the mother and by
others who place their hands over the mother's abdomen.
 The fetus also shows a sensitivity to light and can be stimulated and
irritated. However, it still has a long way to go before it is mature
enough to survive outside of the womb. Although there are a few cases
of infants being born and surviving at this time, the chance of survival
(and without later complications), is very slim.
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FETUS – 6 MONTHS
 The 6th month marks the beginning of the third trimester for the
mother. If born during this trimester, the fetus has a chance survival.
 The point in which it can first survive is referred to as the age of
viability and occurs sometime between 22 and 26 weeks.
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FETUS – 7 MONTHS
 At only 3-4 pounds, the 7 month old fetus has yet another 3-4
pounds to go before reaching the average 7.5 pounds.
 During this time, the brain continues to develop at at
increasingly fast rate.
 By 7 months, the fetus clearly responds to sounds outside of the
womb, developing a preference for the tone and rythm of its
mother's voice.
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FETUS – 8 MONTHS
 By the 8th month, the fetus has little room for large movements.
During this month, a layer of fat is added that will assist with
temperature regulation.
 The lungs however, still remain immature. If born at this time,
the infant will likely require some help with breathing.
 It is not until the 9th month that the lungs are mature enough to
regulate breathing without assistance.
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A CHILD IS BORN
 One minute, and again at five minutes after birth,
the infant is assessed using the APGAR scale.
 On average, the newborn infant weighs 7.5 pounds
and is 20 inches long.
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BABY – 3 WEEKS OLD
 A majority of the newborn's first month is spent sleeping,
waking every few hours to be fed.
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Embrio : blastosis burrows into
the uterine lining
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 As soon as the fertilized egg burrows into the lining, it starts
releasing a pregnancy hormone, HCG (Human Chorionic
Gonadotropin) which sends a message back to the corpus
luteum left behind on the ovarian wall.
 HCG signals the corpus luteum to remain alive beyond its
usual maximum of 16 days and continuing to release
progesterone long enough to sustain the nourishing lining.
 After several months, the placenta takes over, not only
maintaining the endometrium, but providing all the oxygen
and nutrients the fetus needs to thrive.
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Cells Division
 There are two type of cell division

 Mitosis and meiosis
 Reproductive cells divide through meiosis process,
while all other body cells divide through the
mitosis process
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Cells Division
 Mitosis is cell division that results in the duplication of cells; the
daughter cells genetic copies of the parent cell. This cell multiplication
allows for replacement of old cells, tissue repair, growth and
development.
 Mitosis
 The creation of new cells through duplication of chromosomes &
divisions of cells  cells duplicates (From 1 24  16 32,
etc)
 Cells developed into organs, brain, heart etc.
 Growth & Development
 You grew from a zygote, or fertilized egg (the fusion of two cells: an
egg and a sperm) into an organism with trillions of specialized cells.
 Mitosis is the process that enabled you to grow and develop after
that fateful meeting of ovum and sperm became ‘you’.
 Cell Replacement
 Cells must divide in order for an organism to grow and develop, but
cell division is also required for maintenance, cell turnover and
replacement.
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Meiosis is Sex Cell (Gamete) Formation
 In sexually reproducing organisms, some cells are able to divide by another
method called meiosis.
 Meiosis is a complex process by which gametes form; involves duplication
and division of reproductive cells and their chromosomes.
 The number of chromosomes in cells divide into two’s, and each set of
cell will receive 1 from each sets of chromosomes  makes up 23
sets.
 This type of cell division results in the production of gametes (eggs or
sperm).
 Meiosis is much more complex than mitosis involves the duplication and
subsequent division of chromosomes, meiosis involves two divisions of
genetic material. As is the case in mitosis, in meiosis the cell duplicates its
chromosome number prior to beginning cellular division. Then nuclear
division, the sorting out of the genetic material, begins, and unfolds over the
course of 2 cellular divisions that result in 4 gametes.
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Meiosis is Sex Cell (Gamete) Formation
 Gametes & Gonads
 Gametes are haploid (1n) with half the number of chromosomes
than the progenitor cell that they arose from. These haploid sex
cells arise in specialized reproductive tissue called the gonads.
Ovaries (female gonads) and testes (male gonads) are the sites of
meiosis.
 Fertilization & Development
 Sexual reproduction results in the merging of sperm and egg at
fertilization, and brings the chromosome count back to the 2n
diploid number necessary for a zygote to have complete genetic
information; 2 sets of genetic instructions in 23 pairs of
chromosomes.
 As cells divide, the zygote develops and grows into an embryo,
fetus and beyond. These 23 pairs of chromosomes are duplicated
with every cell division, and are the genetic material inside nearly
every cell of theSITINOR/FEM3101/FEBRUARI
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What's the Difference between
Mitosis & Meiosis
 Mitosis is how the cells of our body make
more cells for growth, development and
repair.
 Meiosis is how our body makes sex cells,
or gametes (eggs or sperm).
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Mechanisms of Heredity
 The Genetic Code
 Basis of heredity is a chemical called deoxyribonucleic acid
(DNA), which contains all the inherited material passed from
biological parents to children
 Every cell except the sex cells has 23 pairs of chromosomes-46 in all
 Genetic action that triggers growth of body and brain is often
regulated by hormones
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Mechanisms of heredity
 The genetic code
 DNA and chromosomes
 Human genome
 23 pairs of chromosomes in every cell (46 total)
– except sex cells


Meiosis – division in sex cells (23 single chromosomes)
Mitosis – division in body cells
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Genetic Code
 Genetic information are kept in chromosomes 
ie. A long & complex set of DNA molecules.
 Genes is a segment of DNA molecules  contains
instructions for making protein.
 Human being is said to have 100 trillions of cells
in the body  with specific functions; and is
distributed through 46 chromosomes, ie. 23 from
father & 23 from mother.
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Genetic Foundation
 Genotype (genetic makeup)
 Phenotype (observable characteristics)
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Hereditary composition of
the zygote
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What determines sex?
 Autosomes – chromosome pairs 1- 22
 Sex chromosomes – 23rd pair of chromosomes
 XX = female
 Xy = males
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Determination of a child’s sex
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What Determines Sex?
 Sex chromosomes are either X chromosomes or Y
chromosomes
 When an ovum (X) is fertilized by an X-carrying sperm,
the zygote formed is XX, a female
 When an ovum (X) is fertilized by a Y-carrying sperm,
the resulting zygote is XY, a male
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Choromosomes
 Boy or girl?
 Chromosomes determine sex :
 23 pairs of sex chromosomes
 Female : XX pairs of sex chromosomes
 Male
: XY pairs of sex chromosomes
FATHER=XY
XY (male)
MOTHER=XX
XX (female)
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Patterns of Genetic Transmission
 When an offspring receives two contradictory
traits, only one of them, the dominant one
shows itself
 The expression of a recessive trait, occurs
only when a person receives the recessive
traits from both parents
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Dominant and recessive
inheritance
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 What Causes Multiple Births?
 Dizygotic (two-egg) twins=fraternal twins
 Monozygotic (one-egg) twins=identical twins
 The rise in multiple births is due in part to a trend
toward delayed childbearing
 Infertility
 Inability to conceive a baby after 12 to 18 months
of trying
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Genetic and Chromosomal
Abnormalities
 Some defects are due to abnormalities in genes or
chromosomes, which may result from mutations
 Many disorders arise when an inherited predisposition
interacts with an environmental factor, either before
or after birth
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Sex linked inheritance of a birth defect
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Nature and Nurture
 Some Characteristics Influenced by Heredity and
Environment
 Adopted children's IQs are consistently closer to the IQs of
their biological mothers than to those of their adoptive
parents and siblings.
 Monozygotic twins generally look alike; they are also more
concordant than dizygotic twins in their risk for such medical
disorders as hypertension (high blood pressure), heart
disease, stroke, rheumatoid arthritis, peptic ulcers, and
epilepsy
 Heredity seems to exert a strong influence on general
intelligence and also on specific abilities
 A strong hereditary influence on schizophrenia and autism,
among other disorders;
found in families
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