MOD 3

Fertilization

the process by which sperm and ovum—the male and female gametes, or sex cells— combine to create a single cell called a zygote.

Dizygotic twins

(fraternal twins) 

the result of two separate eggs being fertilized by two different sperm to form two unique individuals.

• Develop from 2 sets of egg and sperm

• Same sex or one of each

Monozygotic twins

(identical twins) 

the result of the cleaving of one fertilized egg generally genetically identical.

• Develop from same egg and sperm

• Same sex

MECHANISMS OF HEREDITY*

*the genetic transmission of heritable characteristics from parents to offspring

DNA

The "stuff" of heredity responsible for building and maintaining human structure.

Chromosome

 - Coils of DNA that contains genes.

Genes 

- The functional units of heredity. Each gene is located in a definite position on its chromosome and contains thousands of bases

Human genome 

- The complete sequence of genes in the human body.

autosomes

Twenty-two pairs

sex chromosomes

 twenty-third pair, one from the father and one from the mother

—that govern the baby’s sex.  

alleles

• Genes that can produce alternative expressions of a characteristic are called

• are alternate versions of the same gene.

homozygous

When both alleles are the same,

heterozygous.

when they are different alleles

dominant inheritance

the dominant allele is always expressed, or shows up as a trait in that person.

recessive inheritance,

For the trait to be expressed in _____________________

the person must have two recessive alleles, one from each parent.

GENOTYPES AND PHENOTYPES: MULTIFACTORIAL TRANSMISSION

If you have dimples, that is part of your phenotype, the observable characteristics through which your genotype, or underlying genetic makeup, is expressed. Hidden alleles can float around undetected for generations and then be expressed if both parents carry a hidden copy

Genotype

- part by part/specific

Phenotype 

- manifest ,

 Alleles 

- hidden traits

EPIGENESIS

Mounting evidence suggests that gene expression itself is controlled by a third component, a mechanism that regulates the functioning of genes within a cell without affecting the structure of the cell’s DNA. Genes are turned off or on as they are needed by the developing body or when triggered by the environment.

 Imprinting

 is the differential expression of certain genetic traits, depending on whether the trait has been inherited from the mother or the father.

Epigenesis

(meaning “on, or above, the genome”) refers to chemical molecules (or “tags”) attached to a gene that alter the way a cell “reads” the gene’s DNA.

Genetic abnormalities

Conditions like

• cystic fibrosis,

• anencephaly,

• spina bifida,

• PKU,

• sickle-cell anemia

• Tay-Sachs disease.

Cystic fibrosis 

- Overproduction of mucus, which collects in the lung and digestive tract.

Anencephaly

- Absence of brain tissues; infants are stillborn or die soon after birth

Spina bifida

 Incompletely closed spinal canal, resulting in muscle weakness or paralysis and loss of bladder and bowel control.

Phenylketonuria (PKU) 

Metabolic disorder resulting in mental retardation.

Sickle-cell anemia

Deformed, fragile red blood cells that can clog the blood vessels, depriving the body of oxygen

Tay-Sachs

 disease Degenerative disease of the brain and nerve cells, resulting in death before age 5

Chromosomal abnormalities

typically occur because of errors in cell division, resulting in an extra or missing chromosome.

Trisomy 21 

– extra chromosomes

Down syndrome,

(Trisomy 21 – extra chromosomes)

the most common chromosomal abnormality, accounts for about 40 percent of all cases of moderate-to-severe mental retardation.

XYY

(Jacobs Syndrome) 

- Male; tall stature; tendency toward low IQ, especially verbal.

(Jacobs Syndrome) 

XYY

XXY (Klinefelter Syndrome)

(Klinefelter Syndrome)

- Male; sterility, underdeveloped secondary sex characteristics, small testes, learning disorders.

(Klinefelter Syndrome)

XXY

XO

(Turner Syndrome) 

- Female; short stature, webbed neck, impaired spatial abilities, no

menstruation, infertility, underdeveloped sex organs, incomplete development of secondary sex characteristics.

XO

(Turner Syndrome)

FRAGILE X 

- Minor-to-severe mental retardation; symptoms, which are more severe in males, include delayed speech and motor development, speech impairments, and hyperactivity; the most common inherited form of mental retardation.

Heritability

Behavioral geneticists have developed a means of estimating how much of a trait is due to

genetics and how much is the result of environmental influences by using a concept known as

 concordant

 meaning the same

Reaction range

Range of potential expressions of a hereditary trait.

CANALIZATION

Some traits have an extremely narrow range of reaction. 

The metaphor of _______ illustrates how heredity restricts the range of development for some traits. Highly _______traits, such as eye color, are strongly programmed by genes, and there is little opportunity for variance in their expression.

Genotype-environment correlation

Because genes influence a person’s exposure to particular environments, the environment often reinforces genetic differences.

This is called __________ or __________ covariance, and it works in three ways to strengthen the phenotypic expression of a genotypic tendency:

1. Passive correlations

2. Reactive, or evocative, correlations

3. Active correlations

three ways to strengthen the phenotypic expression of a genotypic tendency:

Passive correlations

- Parents, who provide the genes that predispose a child toward a trait, also tend to provide an environment that encourages the development of that trait. For example, parents who are musically inclined will create an environment in which music is heard regularly, therefore there is a tendency that the child will inherit the parent’s musical talent. Combination of genetic and environmental influences.

Reactive, or evocative, correlations

-Children with differing genetic makeups evoke different reactions from others. Provide special effort to gain particular trait. (opt to despite the differences)

Active correlations

- As children get older and have more freedom to choose their own activities and environments, they actively select or create experiences consistent with their genetic tendencies. You select your environment wherein your genetic is used (tendency to seek out environments compatible with one’s genotype is called niche-picking)

niche-picking

(tendency to seek out environments compatible with one’s genotype is called )

Prenatal development stages

• ● GERMINAL STAGE (conception to 2nd week)

  ● EMBRYONIC STAGE (2nd to 8th week)

  ● FETAL STAGE (8th week to birth)

GERMINAL STAGE

(conception to 2nd week)

EMBRYONIC STAGE

(2nd to 8th week)

FETAL STAGE

(8th week to birth)

Gestation 

– the period between conception and birth. The normal range of gestation is between 37 and 41 weeks (Martin, Hamilton, et al., 2009).

Gestational age 

- is usually dated from the first day of an expectant mother’s

last menstrual cycle.

Tender, swollen breasts or nipples

Increased production of the female hormones estrogen and progesterone stimulates breast growth to prepare for producing milk (most noticeable in a first pregnancy).

Fatigue; need to take extra naps

Woman’s heart is pumping harder and faster to produce extra blood to carry nutrients to the fetus. Stepped-up production of hormones takes extra effort. Progesterone depresses central nervous system and may cause sleepiness. Concerns about pregnancy may sap energy.

Slight bleeding or cramping

Implantation bleeding may occur about 10 to 14 days after fertilization when fertilized ovum attaches to lining of uterus. Many women also have cramps (similar to menstrual cramps) as the uterus begins to enlarge.

Food cravings

Hormonal changes may alter food preferences, especially during first trimester, when hormones have greatest impact.

Nausea with or without vomiting

Rising levels of estrogen produced by placenta and fetus cause stomach to empty more slowly. Also, heightened sense of smell may trigger nausea in response to certain odors, such as coffee, meat, dairy products, or spicy foods. Morning sickness may begin as early as 2 weeks after conception, but usually around 4 to 8 weeks, and may occur at any time of day.

Frequent urination

Enlarging uterus during first trimester exerts pressure on the bladder.

Frequent, mild headaches

Increased blood circulation caused by hormonal changes may bring these on.

Constipation

Increase in progesterone may slow digestion, so food passes more slowly through intestinal tract

Mood swings

Flood of hormones early in pregnancy can produce emotional highs and lows.

Faintness and dizziness

Lightheaded feeling may be triggered by blood vessel dilation and low blood pressure or by low blood sugar.

Raised basal body temperature

Basal body temperature (taken first thing in the morning) normally rises soon after ovulation each month and then drops during menstruation. When menstruation ceases, temperature remains elevated

Human chorionic gonadotropin (HCG)

is only produced by embryos and fetuses.

False positive

(not possible)

– nadetect HCG pero di nagdevelop cell

False negative

– Too early PT

 GERMINAL STAGE

- is the first stage of prenatal development, during which the dividing mass of cells has implanted itself in the uterine wall. Before implantation, some cells around the blastocyst cluster on one side to form the embryonic disk: a thickened cell mass from which the embryo begins to develop.

EMBRYONIC DISK

Ectoderm (upper) outer skin, sensory organs, nervous system

Mesoderm (middle) inner skin, muscles, skeleton, excretory system, circulatory system

Endoderm (inner) respiratory system, digestive system

Ectoderm

(upper) outer skin, sensory organs, nervous system

Mesoderm

(middle) inner skin, muscles, skeleton, excretory system, circulatory system

Endoderm

(inner) respiratory system, digestive system

Implantation

occurs when a fertilized egg (zygote) attaches to the lining of your uterus

EMBRYONIC STAGE

- the stage that lays the necessary groundwork for all of the remaining stages of life. After a blastocyst implant in the uterus around the end of the first week after fertilization, its internal cell mass is now known as the embryo.

Organogenesis

- when organs develop within the newly formed germ layers (organs are visible; developed)
- Structures and organs like the neural tube (which later becomes the brain and spinal cord), head, eyes, mouth and limbs form.

 FETAL STAGE

(“finishing touches”)

- the third stage of prenatal development, during which the organs and body systems become more complex.

Embryo to Fetus

- The early body systems and structures established in the embryonic stage continue to develop

Reflexes

- Between the ninth and twelfth week of gestation (at the earliest), reflexes begin to emerge. The fetus begins to make reflexive motions with its arms and legs.

Teratogen

- an environmental agent, such as a virus, a drug, or radiation, that can interfere with normal prenatal development. However, not all environmental hazards are equally risky for all fetuses.

An event, substance, or process may be teratogenic for some fetuses but have little or no effect on others. (Toxoplasmosis – severe impairments to baby)

 NUTRITION AND MATERNAL WEIGHT

- Pregnant women typically need 300 to 500 additional calories a day, including extra protein. Women of normal weight and body build who gain 16 to 40 pounds are less likely to have birth complications or to bear babies whose weight at birth is dangerously low or overly high.

PHYSICAL ACTIVITY AND STRENUOUS WORK

- Moderate exercise any time during pregnancy does not seem to endanger the fetuses of healthy women. Employment during pregnancy also generally entails no special hazards. However, strenuous working conditions, occupational fatigue, and long working hours may be associated with a greater risk of premature birth.

DRUG INTAKE

- Practically everything an expectant mother takes in makes its way to the uterus. Drugs may cross the placenta, just as oxygen, carbon dioxide, and water do. Vulnerability is greatest in the first few months of gestation, when development is most rapid.

Acquired immune deficiency syndrome (AIDS)

- If an expectant mother has the virus in her blood, perinatal transmission may occur: the virus may cross over to the fetus’s bloodstream through the placenta during pregnancy, labor, or delivery or, after birth, through breast milk.

Rubella

(German measles)

- if contracted by a woman before her 11th week of pregnancy, is almost certain to cause deafness and heart defects in her baby.

 Toxoplasmosis 

–

infection that can cause severe impairments to the baby. caused by a parasite harbored in the bodies of cattle, sheep, and pigs and in the intestinal tracts of cats.

diabetes

Offspring of mothers with ______ are also 3 to 4 times more likely than offspring of other women to develop a wide range of birth defects.

MATERNAL ANXIETY, STRESS, AND DEPRESSION

• A mother’s self-reported stress and anxiety during pregnancy has been associated with more active and irritable temperament in newborns (DiPietro et al., 2010), inattentiveness during a developmental assessment in 8-month-olds, and negative emotionality or behavioral disorders in early childhood.

Chronic stress

can result in preterm delivery, perhaps through the action of elevated levels of stress hormones or the resulting dampened immune functioning.

• Also, major stress during the 24th to 28th weeks of pregnancy has been implicated in autism

MATERNAL AGE

The risk of miscarriage reaches 90 percent for women aged 45 or older. Women 30 to 35 are more likely to suffer complications due to diabetes, high blood pressure, or severe bleeding. There is also higher risk of premature delivery, retarded fetal growth, birth defects, and chromosomal abnormalities, such as Down syndrome

 Adolescent mothers

 Adolescent mothers tend to have premature or underweight babies—perhaps because a young girl’s still-growing body consumes vital nutrients the fetus needs.

OUTSIDE ENVIRONMENTAL HAZARD

• Air pollution, chemicals,

• radiation, extremes of heat and humidity,

• other environmental hazards can affect prenatal development.

• In utero exposure to radiation 8 through 15 weeks after fertilization has been linked to mental retardation, small head size, chromosomal malformations, Down syndrome, seizures, and poor performance on IQ tests and in school

Fetal Radiation Exposure

Exposure to radiation between 8 and 15 weeks after fertilization linked to mental retardation, small head size, chromosomal malformations, Down syndrome, seizures, and poor performance on IQ tests and in school.

FETUS IN UTERO

ANATOMY

• Amniotic sac

• Amnion

• Chorion

• Cervix

• Placenta

• Umbilical cord

• Uterus

Amniotic Sac

 - a thin-walled sac that surrounds the fetus during pregnancy. The sac is filled with liquid made by the fetus (amniotic fluid) and the membrane that covers the fetal side of the placenta (amnion). This protects the fetus from injury. It also helps to regulate the temperature of the fetus.

(amniotic fluid)

a thin-walled sac that surrounds the fetus during pregnancy. The sac is filled with liquid made by the fetus

amnion

This protects the fetus from injury. It also helps to regulate the temperature of the fetus.

filled with fluid that provides cushioning to the developing embryo

Chorion

 forms a protective covering for the developing embryo. (outer part)

Cervix

The lower part of the uterus that extends into the vagina. The cervix is made up of mostly fibrous tissue and muscle. It is circular in shape.