Transcript Life begins with genes

Chapter 2 Genes and Parental
Development
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Development Parenting styles Cognition
DNA
Theories of development Conception
Genes
Developmental theorists Assimilation
Genotype Teratogenic effects Threshold effect
Phenotype Imprinting
Accommodation
Gamete
Stranger anxiety Germinal stage
Zygote
Embryonic stage
Attachment Theory of mind Fetal stage
Interaction effect Apgar scale Critical periods
Addiction
Dizygotic/Monozygotic twins
Life begins with genes
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What are genes?
All living things are made up of cells
The work of body cells is done by proteins
Instructions for manufacturing proteins are
stored in molecules of DNA
• The instructions are transmitted to cells via 4
chemical bases
• DNA is composed of a sequence of amino
acids- adenine, thiamine, cytosine, and
guanine
• Genome- the sum total of genetic instructions for a
living organism
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• Genes- how the instructions in the are organized
(units)
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• Every human body cell, except sperm and ovum, has 23
pairs of chromosomes
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• Where do these pairs come from?
• the parents
• The sperm and ovum receive only one
member of each chromosome pair when cells
divide to produce gametes, and thus have
only 23 single chromosomes each
• What is a gamete?
• Gamete- a reproductive cell, a sperm or ovum
that can produce a new individual if it
combines with a gamete from the other sex to
make a zygote
• Zygote- the single cell formed from the fusing
of two gametes, a sperm & an ovum
How does conception occur?
• Conception occurs when the male gamete (or
sperm) penetrates the membrane of the female
gamete (the ovum); the gametes fuse and their
genetic material combines to form one zygote
• This process makes up the organism’s genetic
inheritance, or genotype
• Genotype- an organism’s entire genetic
inheritance, make-up, or potential
• Phenotype refers to the observable
characteristics and behaviors of a person
• (appearance, personality, intelligence, etc)
How is sex determined?
• The 23rd pair of chromosomes determines the
sex
• The chemical on the Y chromosome signals
the development of the male organs
• The chromosomal make up is XY in the male
• and XX in the female
• In a stressful pregnancy, XY embryos are more
likely than XXs to be expelled in a
spontaneous abortion, or miscarriage
• Within hours, the zygote initiates human
development through the process of
duplication and division
• Implantation begins about 10 days after
conception, the organism buries into the
placenta for nourishment
• Then differentiation begins, this is when cells
begin to specialize, taking different forms and
reproducing at various rates
• At the eight-cell stage, the organism has stem
cells it could develop into a body part
• The cells on the outer side of the of the mass
become the placenta-the organ that will
support the life
• Certain genes begin to switch on an off during
this developmental stage
• Most traits are polygenic- affected by many
genes and are multifactorial- influenced by
many factors…to include factors in the
environment
What is the Human Genome Project?
• It is the international effort to map the complete
genetic code
• This map has already revealed that all living creatures
share genes; the more closely related to the organism,
the more genes they share
• Humans have about 25,000 genes
• (additive genes-a type of genetic interaction, the
various genes underylying skin color and height)
additive genes adds something to the
phenotype;height, hair curliness
• Genes that have a controlling influence over weaker,
recessive genes are called dominant genes, recessive
genes are non additive; Blood type B and Rh-positive
• The recessive genes for some forms of color
blindness, many allergies, some learning
disabilities, and several diseases are X-linked (
they are only located on the X chromosome)
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• Because males only have one X chromosome,
they are more likely than females to manifest
these characteristics in their phenotype
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• Why is this?
Twins
• In some pregnancies, a single zygote splits into two
separate identical cells that develop into genetically
identical or monozygotic (MZ) twins
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• MZ twins have the potential for developing the same
physical appearance and psychological characteristics, but
they are also vulnerable to specific diseases
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• Dizogotic (DZ) or fraternal twins begin life as separate
zygotes, and share no more genes than any other sibling
(about 50 percent)
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• Clone- a clone is a an organism that is produced from
another organism through artificial replication of cells and
is genetically identical to the organism
Gene-Environment interaction
• People are carriers of unexpressed genes
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• Genes are part of a person’s basic foundation, affecting
many aspects of life while determining none… even
traits that show a strong genetic influence are also
affected by the environment
• How is addiction involved?
• Addiction is an example of a gene-environment
interaction
• some people have a biological disposition toward
alcoholism and given the right environmental
circumstances may succumb to the disease and the
genetic susceptibility may be expressed through
alcoholism
Chromosomal abnormalities
• Some gametes may have more or fewer than 23
chromosomes, many factors are responsible, both
inherited or environmental
• For instance type 2 diabetes does not begin unless a
person is both genetically vulnerable and has more
body fat than is ideal for his or her age and height
• An estimated half of all zygotes have too few or too
many chromosomes…most of the time these zygotes
do not develop, or come to term due to spontaneous
abortion
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• However, once in every 200 births, a baby is born with
a chromosomal abnormality that leads to a
recognizable syndrome
• Zygotes that are formed from abnormal or fragile gametes
may not duplicate, divide, or differentiate
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• * the variable that most often correlates with
chromosomal abnormalities is the mother’s age
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• The most common of the extra-chromosome syndrome is
Down Syndrome (trisomy 21)
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• Persons with Down Syndrome exhibit distinguishing
features of the slanted eyes, rounded face, and a thick
tongue
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• the extra chromosome at site 21 also makes them more
susceptible to heart defects, slow intellectual development,
and by middle age Alzheimer’s disease it’s inherited
• *people with this syndrome age faster than other adults
about 1 in 500 infants is either missing a sex chromosome or
has two or more of them
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Turner syndrome- a girl has only 1 X chromosome resulting in
XO, the female may be unusually short, or the genitals may be
underdeveloped she can’t conceive or bear children and she
may be slow to develop in spatial understanding
Klinefelter syndrome-a boy inherits the XXY pattern,
symptoms may also include learning problems this syndrome
may not be detected until puberty
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Hemophilia is also a sex-linked condition in which the blood
does not coagulate
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Hormone therapy and psychological counseling are
beneficial for persons suffering from these disorders
• Most of the known genetic disorders are dominant and usually not
seriously disabling…2 exceptions are Huntington’s disease and
Tourette syndrome a dominant disorder
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• Although most known genetic disorders are dominant, recessive
disorders such as cystic fibrosis, thalassemia, and sickle-cell
anemia claim the lives of both men and women
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• Those who feel that they may be at risk for giving birth to a child
with a genetic problem may elect to pursue genetic counseling
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• Genetic counseling- a means by which couples can learn more
about their genes and make an informed decision about
childbearing
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• Genetic testing for genetic disorders are also beneficial especially
for detecting the genetic disorder PKU northern Europeans are at
risk, severely retarded
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Birth, Early Infancy
• The 1st 2 weeks of prenatal development are
called the germinal period
• The embryonic period begins in the 3rd week
as the formless mass becomes a distinct
being, which is now referred to as an embryo
• A thin line down the middle of the outer layer
of cells is the primitive streak, and the
structure becomes the neural tube, then the
brain and spinal column (the central nervous
system)
• In the 4th week, the cardiovascular system is
functioning; the eyes, ears, nose, and mouth
start to form
• At 5 weeks, the arm and leg buds appear and
the primitive heart is now visible
• By the end of the 2nd month, the developing
organism weighs about 1 gram, is 2 ½
centimeters long, and has all the basic organs
and body parts of a human being, and a
unisex structure called the indifferent gonad
• The fetal period-from the 9th week after
conception, the sex organs begin to take
shape
• By the 12th week, the genitals are fully formed
• A sonogram is readable
• By the 12th week, the genitals are fully formed
• A sonogram is readable
• Again, if the fetus is male (XY), the SRY gene
on the Y chromosome signals the
development of the male sex organs
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• If the fetus is female (XX), no signal is sent,
and the fetus begins to develop female sex
organs
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• Most functions of the brain are genderneutral; some sex differences in brain
organization occur in mid pregnancy
How the brain develops
• At the end of the 3rd month, the fetus has all its body
parts
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• *22 weeks-signals the age of viability- the ability of the
fetus to live outside of the body
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• During this time, the brain develops new neurons in a
process called neurogenesis and new connections
between them in a process called synaptogenesis
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• Weight gain during the final 3 months is 41/2 pounds
• The neurological, respiratory, and cardiovascular
systems mature dramatically; brain growth is so
extensive that the brain’s cortex must fold into layers in
order to fit into the skull
Teratogens
• What are teratogens?
• Teratology is the study of birth defects; teratogens
include such substance as viruses, drugs, chemicals,
stressors, and environmental hazards that can impair
developmental and lead to birth defects and even
death
• 3 crucial factors that determine whether a specific
teratogen will cause harm, and of what nature are:
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1. the timing of exposure
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2. the amount of exposure
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3. the developing organism’s genetic
vulnerability to damage from the substance
• The critical periods are times when the body is most
susceptible to teratogenic damage
• For behavioral teratogens that affect the brain and
nervous system, the entire prenatal period is critical
• For some teratogens, the threshold effect is
imperative; this means that the substance is not
harmful until the chemical reaches a certain level
• The interaction effect of teratogens occurs when one
teratogen intensifies the impact of the other
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• Males not only have a higher rate of teratogenic birth
defects, learning disabilities, and later teratogenrelated behavioral problems, but also a higher rate of
spontaneous abortions
• Early prenatal care to include folic acid intake, can
prevent the impact of some deadly teratogens
• The pax6 gene is common in nearsightedness
• the Birth Process
• Birth begins at about 38 weeks after conception
when the fetus’s brain signals the release of
hormones that trigger uterine contractions in the
mother
• There are many choices for women in how and
where they give birth such as the doula, midwife,
or hospital birth
The Apgar Scale
• What is the apgar scale?
• The Apgar scale is used to assign a score of between 0
and 2 to the newborn’s heart rate, breathing, muscle
tone, color, and reflexes at one minute after birth and
again at 5 minutes
• *A score of 7 or better indicates the newborn is not in
danger
• *A score of below 7 indicates that the infant needs
help in establishing normal breathing
• *A score of below 4 indicates that the baby is in critical
condition and needs immediate medical attention
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• Cesarean sections account for about 28% of U.S. births;
& 1% of births take place at home
Birth Complications
• Birth complications are more likely if the fetus is already at risk because
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• 1. low birthweight (LBW)-birth weight that is less than 5 ½ pound
• very low birthweight (VLBW)-less than 3 pounds
• extremely low birthweight (ELBW)-less than 2 pounds
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• 2. Preterm birth
• 3. Genetic abnormality
• 4. Teratogenic exposure
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• Nurture not nature is typically responsible for low birthweight maternal
illness, infection, malnutrition
• In Africa, November newborns are most likely to die because they are
born at the end of the hungry season
• Mother’s age (too young or old) and health is also a factor
• Strong parental alliance is important in the birth experience of both
parents that can reduce LBW babies (prenatal care, pregnancy
classes) and working together can lead to parental involvement
through kangaroo care
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• The father plays a pivotal role in the mental health of the pregnant
woman encouragement, protection, etc
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• Parental involvement can also help with post partum depression
detection
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• Extensive research shows that events that occur right after birth are
just one episode in a long-term process of bonding between parent
and infant bonding can increase the chance of survival if the mother
bonds with the infant, skin on skin contact
• Cross-fostering monkeys taken, bonding sometimes occurs