Transcript Genetics and Heredity - Flushing Community Schools

Chapter 4: Pregnancy
- Genetics and Heredity
What person in your family do you
most closely resemble, both
physically, and in terms of your
personality? What do the two of you
have in common?
Conception
• Zygote: the cell that forms when a sperm fertilizes an egg
• Monozygote: Identical Twins (1 egg + 1 sperm) Fertilized
ovum splits into two identical cells – Always the same gender
• Dizygote: Fraternal Twins (2 different eggs + different sperm)
-- The twins will look different, may be the same gender, may
not be.
• Multiple Birth: More than two babies
– May be identical, fraternal, or both
• Conjoined Twins: Ovum splits apart, but the separation is
not complete. Babies are joined at some part(s) of their
bodies
Genetics and Heredity
• Genetic factors: The traits passed through the genes
– Traits Include: Eye color, hair color, height, body build,
blood types
• Heredity: Characteristics that a child receives from both
parents
Chromosomes and Genes
Chromosomes-threadlike structures that carry genes in living
cells.
• Half (23) come from the mother and half (23)come
from the father
• Each chromosome contains about 20,000 genes
A child’s traits are passed through the parents germ cells
(ovum and sperm) only half will be present in the
child’s traits.
GENES
• Dominate Gene: More powerful, Trait actually seen in a person
• Recessive Gene: Weaker Gene. It hides in the background. A recessive gene can
only determine a characteristic when two recessive genes are present.
• Carrier: Has a recessive gene that is not present.
• Sex-Linked: For instance, a mother passes the recessive X gene to her son.
– A color-blind male receives this trait from his mother, but she is usually not
color-blind herself.
Eye Color Possibilities for their Children:
Mother: Brown Eyes (Bb)
Father: Blue Eyes (bb)
Bb: Brown Eyes (B is the Dominate Trait)
bb: Blue Eyes (b is the Recessive Trait)
Baby Boy or Baby Girl ???
• Conception is the union of the Egg and Sperm
• Female Sex Cells (XX) Egg/Ovum
• Male Sex Cells (XY) Sperm
Mom XX
Dad XY
Baby Girl XX
Mom XX
Dad XY
Baby Boy XY
• Gender is determined by the FATHER 
Factors that Contribute to Multiple
Births
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Family History
Naturally Increased Hormones
(More than 1 egg released)
Fertility Drugs
Maternal age: Mother’s between the ages of 35 and 40 rates double
Likelihood of Multiple Pregnancies in the U.S.
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Twins: Caucasians 1 in 83
Triplets: 1 in every 7,000births
Quadruplets: 1 in every 572,000 births
Quintuplets: 1 in every 47.5 million
Sextuplets: 1 in every 4 billion
Stages in Prenatal Development
• Prenatal Development-development that takes places between conception
and birth
– Three stages:
• Germinal stage-conception through the first two weeks of the
pregnancy
– Cell division occurs
– Egg becomes embedded in the uterine wall
– Amnion (fluid-filled sac)-surrounds the baby to protect it
– Placenta(organ filled with blood)-nourishes the baby and
removes wastes
– Umbilical cord-connects the child to the placenta
Embryonic Stage
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Most critical stage
Lasts six weeks (2 weeks through 8 weeks)
Baby is called an embryo.
Arms, legs, fingers, toes, and face develop
Heart, brain, and lungs also develop
No bones yet, but cartilage provides the body structure.
Fetal Stage
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9 weeks through 40 weeks
Baby is called a fetus
Able to hear the baby’s heartbeat at a doctor’s visit
Between months 4-5 the mother will feel the baby move(quickening)
The baby can turn, swallow, and suck its thumb.
Age of viability- 7 months or 28 weeks, age at which most babies could
survive if they were born.
Fetal Development
Month by Month
First Month
• By the end of the
first month, the
embryo is about
1/10 of an inch
long. The heart,
which is no larger
than a poppy seed,
has begun beating.
• Mother-Missed
period
First Month
(four weeks)
Two Months
• The embryo is about
1 inch long and has
distinct, slightly
webbed fingers.
Veins are clearly
visible. The heart
has divided into right
and left chambers.
• Mother-breasts
swell, fatigue,
morning sickness
Two Months
Three Months
• By now the fetus is 2
1/2 to 3 inches long
and is fully formed.
He/She has begun
swallowing and kicking.
All organs and
muscles have formed
and are beginning to
function.
• Mother-breasts ache,
abdomen grows, 2-4lbs
weight gain.
Three Months (12 weeks)
Four Months
• Your baby is
covered with a layer
of thick, downy hair
called lanugo. His
heartbeat can be
heard clearly. This is
when you may feel
your baby's first
kick.
• Mother-Size change,
increased appetite.
4 months
Five Months
• A protective coating
called vernix caseosa
begins to form on
baby's skin. By the end
of this month, your baby
will be nearly 8 inches
long and weigh almost
a pound.
• Mother-obvious large
abdomen, 10-12 lbs.
weight gain.
5 months (20 weeks)
Six Months
• Eyebrows and eyelids
are visible. Your baby's
lungs are filled with
amniotic fluid, and he
has started breathing
motions. If you talk or
sing, he can hear you.
• Mother-Fetal movement is
strong. Fetus kicks and
thumps are felt.10-12
pounds weight gain.
6 Months
Seven Months
• By the end of the
seventh month, your
baby weighs about 3
1/2 pounds and is
about 12 inches
long. His body is
well-formed.
Fingernails cover
his fingertips
• Mother-Posture is affected
by increased weight and
size.
7 months (28 Weeks)
Eight Months
• Your baby is gaining
about half a pound per
week, and layers of fat
are piling on. He has
probably turned headdown in preparation for
birth. He weighs
between 4 and 6
pounds.
•
Mother-Backaches, leg cramps,
shortness or breath, fatigue.
Fetal kicks are felt. Weight gain
of 18-20 pounds.
Nine Months
• Your baby is a hefty 6
to 9 pounds and
measures between 19
and 22 inches. As he
becomes more
crowded, you may feel
him move around less.
Mother-“Lightening” – the fetus
drops into the pelvis.Easier to
breathe.Usual discomforts of late
pregnancy.Weight gain of 24-30
pounds.Uterus is the size of a small
watermelon.May have false labor.
Birth!