Did you know Identical twins may not be exactly identical All but 300 human genes have counterparts in mice Birth defects do not always appear at birth Fetuses can learn and remember while in the womb and they respond to their mothers voice ID: 653128
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Prenatal Development
Chapter 4Slide2
Did you know….
“Identical twins” may not be exactly identical?
All but 300 human genes have counterparts in mice?
“Birth defects” do not always appear at birth?
Fetuses can learn and remember while in the womb, and they respond to their mother’s voice?
Drinking or smoking during pregnancy can do permanent damage to an unborn child?
Prenatal care should begin before conception?Slide3
Roles of Genetics
Why do I have this hair color?
Why do I have blue eyes like my mom instead of brown eyes like my dad?
People inherit many physical traits from their parents.
Traits can include skin color, hair texture and color, eye color, the size and shape of ears, and more.Slide4
At the moment of conception, every human baby receives 46 chromosomes.
Chromosomes are a tiny threadlike structure in the nucleus of every cell
You get 23 from each parent
Gene is a unit that determines a human’s inherited characteristics
DNA is the complex molecules that make up your genes
Your 46 chromosomes form your unique DNA
No two people, except identical twins, have identical DNASlide5
What determines Sex?
Autosomes:
the 22 pairs of chromosomes not related to sexual expression
Sex chromosomes:
Pair of chromosomes that determines sex: XX in the normal female, XY in the normal male
X chromosomes:
chromosomes containing the genes for femaleness
Y chromosomes:
chromosomes containing the genes for maleness
Wnt-4:
a signaling molecule that appears to control the development of female characteristicsSlide6
Patterns of Genetic Transmission
1.
Dominant inheritance:
pattern of inheritance in which a child receives matching dominant alleles, or when a child receives contradictory alleles. In either case, the dominant characteristic is expressed.
Recessive inheritance:
pattern of inheritance in which a child receives identical recessive alleles, resulting in expression of a non-dominant trait
Mutations:
permanent alterations in genetic material that occur spontaneously or due to environmental hazardsSlide7
Chromosomal Abnormalities
Defects
Transmitted by Dominant or Recessive Inheritance
Down syndrome:
Chromosomal disorder characterized by moderate-to-serve mental retardation and by such physical signs as a downward-sloping skin fold at the inner corners of the eyes
Trisomy 21:
another name for Down syndrome, in which there is an extra of the21
st
chromosome or a translocation of part of the 21
st
chromosome onto another chromosomeSlide8
What Causes Multiple Births?
Dizygotic (two-egg) twins:
Twins conceived by the union of two different ova with two different sperm cells; Also called
Fraternal twins
Monozygotic (one-egg) twins:
Twins resulting from the division of a single zygote after fertilization; also called
Identical twins
Temperament:
Characteristic disposition or style of approaching and reacting to situations.
Semi-
identical-twins- the result of two sperm cells fusing with a single ovum. Slide9
Conceiving New Life
How Fertilization Takes Place
Fertilization: Combining sperm and ovum to produce a zygote; also called
conception
Gametes:
The sex cells, ovum and sperm
Zygote:
Single-celled organism resulting from fertilization
Follicle:
Small sac in the ovary containing the immature ova
Ovulation:
The rupture of a mature follicle and expulsion of the ovum.
Cilia:
Tiny hair cells in the fallopian tubes that sweep the ovum along
Cervix:
The opening of the uterus. Slide10
Infertility
Not all couples who want to become parents are able to have a child.
Infertility is the inability to conceive a child.
40% of cases are due to female infertility
40% of cases are due to male infertility
20% have unknown causes or are linked to both partners
Options for infertile couples
Adoption
Artificial insemination: dr. injects sperm into the woman’s uterus
In Vitro Fertilization: dr. combines a mature ovum from the woman
wht
sperm from her husband. Pregnancy occurs if fertilized egg attaches itself to the uterus
Ovum Transfer: similar to in-vitro, except an ovum from another woman is donated
Surrogate Mother: A surrogate is a substitute. Where another woman becomes pregnant for the woman that can’t conceive. Legal arrangements are required.Slide11
Prenatal Development
The baby’s development during a pregnancy is called prenatal development
Often grouped into 3 stages
Germinal stage
Embryonic stage
Fetal stage
Gestation:
the approximately 9 month period of development between conception and birth
Gestational age:
Measurement of development from conceptionSlide12
Germinal stage: Fertilization to 2 weeks
1. Germinal Stage (Fertilization to 2 weeks)
Germinal stage: first two weeks of prenatal development, characterized by rapid cell division, and implantation in the wall of the uterus
Cell Division:
Mitosis:
Period of rapid cell division and duplication
Blastocyst:
A Fluid-Filled sphere of cells that will float into the uterus and implant in the lining.
Embryonic disk:
A thickened cell mass located on the blastocyst, from which the embryo begins to develop
Ectoderm:
The upper layer of the embryonic disk that will form into the outer layer of skin, the nails, hair, teeth, sensory organs, and the nervous system .
Implantation: the lining of the uterus has thickened enough for the zygote to attach. Despite the rapid growth the zygote is only the size of the head of a pin.Slide13
Embryonic Stage (2 to 8 Weeks)
Embryonic stage: second stage of gestation (2 to 8 weeks), characterized by rapid growth and development of major body systems and organs (developing baby is now called a fetus)
Trimester:
A 3-month period of pregnancy
Organs and body systems: the cells begin to separate and develop into the major systems of the human body.
Include the heart, lungs, bones, and muscles.
About 27 days after conception, the neural tube has closed. The neural tube is a tube in the back of the developing baby that will become the brain and spinal cordSlide14
Stages of Prenatal Development
Endoderm:
The lower layer of the embryonic disk that will form into the digestive system, liver, pancreas, salivary glands, and respiratory system
Mesoderm:
The inner layer of the embryonic disk that will form into the inner layer of skin, muscles, skeleton, and excretory and circulatory systems
Placenta:
Organ that provides oxygen and nourishment to the developing baby and removes it body wastes
Umbilical cord:
Cord that connect and vice versa
Amniotic sac or Amniotic cavity:
Fluid-filled membrane that encases the developing baby, protecting it and giving it room to move
Amnion and
chorion
:
Outer layers of amniotic sacSlide15
Fetal Stage (8 weeks to Birth)
Fetal stage: Final stage of gestation (from 8 weeks to birth), characterized by increased detail of body parts and greatly enlarged body size
Ultrasound:
Prenatal medical procedure using high-frequency sound waves to detect the outline of a fetus and its movements, to determine whether a pregnancy is progressing normally
Making movement: sometime during 4
th
and 5
th
month, the kicks and other movements of the fetus touch the wall of the uterus. During this time parents talk, read, or sing to the developing fetus to encourage movement.
Fetus: has all 5 senses, can cry, and sleeps 90% of the day.
During the 8
th
month the baby settles into the proper position for delivery Slide16
Fetal stage
Growing Bigger: as the fetus grows so does the amniotic fluid and the uterus
Ready for birth: the common length for pregnancy is about 40 weeks, or 280 days, from the first day of the last menstrual cycle.
By the 9
th
month the fetus is fully developed and can usually survive outside of the womb. Slide17
Environmental Influences: Maternal Factors
Teratogenic
:
Capable of causing birth defects
Transforming growth factor alpha:
A variant of a growth gene, this factor causes a fetus to have six times more risk than other fetuses of developing a cleft palate if the mother smokes while pregnant.
1. Nutrition and Maternal weight
2. Malnutrition
3. Drug Intake
A. Medical Drugs
B. Alcohol
Fetal alcohol syndrome (FAS):
Combination of mental, motor, and developmental abnormalities affecting the offspring of some women who consume alcohol during pregnancy
C. Nicotine
D. Caffeine
E. Marijuana, Cocaine, and MethamphetamineSlide18
4. Mental Illness
Acquired immune deficiency syndrome (AIDS): Viral disease that undermines functioning of the immune system.
Perinatal transmission: Virus may cross over to the fetus’s bloodstream through the placenta during pregnancy, labor, or delivery or, after birth, through breast milk
Toxoplasmosis: An infection caused by a parasite harbored in the bodies of cattle, sheep, pigs, and in the intestinal tracts of cats.
5. Maternal Stress of Anxiety
6. Maternal Age
7. Outside Environmental Hazards
Paternal Factors