MOD 3

DEVELOPMENT PSYCHOLOGY MODULE 3: FORMING A NEW LIFE

CONCEIVING NEW LIFE

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

THE GENETIC CODE

• DNA - The “stuﬀ” of heredity responsible for building and maintaining your 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.

PATTERNS OF GENETIC TRANSMISSION

• 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.

P.S Genotypes - 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. 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

• 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

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

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

NATURE AND NURTURE: INFLUENCES OF HEREDITY AND ENVIRONMENT STUDYING HEREDITY AND ENVIRONMENT

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 heritability.

By looking at groups of people with known genetic relationships, and assessing whether or not they are concordant, meaning the same, on a given trait, behavioral geneticists can estimate the relative influence of genes and environment.

HOW HEREDITY AND ENVIRONMENT WORK TOGETHER

REACTION RANGE a range of potential expressions of a hereditary trait. CANALIZATION Some traits have an extremely narrow range of reaction. The metaphor of canalization illustrates how heredity restricts the range of development for some traits. Highly canalized 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 genotype-environment correlation, or genotype-environment covariance, and it works in three ways to strengthen the phenotypic expression of a genotypic tendency:

1. 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.

2. Reactive, or evocative, correlations - Children with diﬀering genetic makeups evoke diﬀerent reactions from others

3. 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.

PRENATAL DEVELOPMENT

STAGES OF PRENATAL DEVELOPMENT

● GERMINAL STAGE (conception to 2nd week)

● EMBRYONIC STAGE (2nd to 8th week)

● FETAL STAGE (8th week to birth)

1. 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

IMPLANTATION

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

2. EMBRYONIC STAGE - the stage that lays the necessary groundwork for all of the remaining stages of life.

After a blastocyst implants 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

Structures and organs like the neural tube (which later becomes the brain and spinal cord), head, eyes, mouth and limbs form.

3. FETAL STAGE - 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.

During the third month of gestation, the sex organs begin to diﬀerentiate. By the end of the month, all parts of the body will be formed.

ENVIRONMENTAL INFLUENCES: MATERNAL FACTORS

• 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.

• 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.

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 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, and 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

FETUS IN UTERO ANATOMY

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.

amnion: filled with fluid that provides cushioning to the developing embryo

chorion: forms a protective covering for the developing embryo

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.

Placenta. An organ shaped like a flat cake. It only grows during pregnancy. The fetus takes in oxygen, nutrients, and other substances from the placenta and gets rid of carbon dioxide and other wastes

Umbilical cord. A rope-like cord connecting the fetus to the placenta. The umbilical cord contains 2 arteries and a vein. It carries oxygen and nutrients to the fetus and waste products away from the fetus.

Uterus. The uterus, or womb, is a hollow, pear-shaped organ in a woman's lower stomach between the bladder and the rectum. It sheds its lining each month during menstruation. A fertilized egg (ovum) becomes implanted in the uterus, and the fetus develops.

● Medical Drugs

● Alcohol

● Nicotine

● Caﬀeine

● Marijuana, Cocaine, and Methamphetamine

MATERNAL ILLNESSES

• 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.

• An infection called toxoplasmosis can cause severe impairments to the baby. Oﬀspring of mothers with diabetes 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