chapter three

fertilization

the union of sperm and ovum to produce a zygote; also called conception

Prenatal care

- Education, Social services, Nutritional services
2. Helps protect the life & health of the infant & mother.
3. Not evenly distributed among SES, ethnic groups

Preconception Care

- Physical examinations
- Vaccinations
- Risk screening
- Counseling

Disparities in Prenatal Care

1. Lacks uniform national standards & guaranteed financial coverage.
2. Rise of low birth weights, possible reached a plateau?
3. Higher risk groups may not have access to prenatal care.

Monitoring Prenatal Development

1. Ultrasound & amniocentesis
2. Chorionic villus sampling (CVS)
3. Embryoscopy
4. Maternal blood test

Environmental Influences: Paternal Factors

May affect quality of sperm:
- Exposure to lead
- Marijuana or tabacco smoke
- Alcohol or radiation
- Pesticides
- Paternal age

Environmental Influences: Maternal Factors

- Teratogen
- Nutrition & maternal weight
- Drug & alcohol intake (Fetal alcohol syndrome)
- Nicotine
- Caffeine
- Maternal illnesses (HIV/AIDS)
- Maternal age & stress
- Outside environment hazards

Fetal Stage Development

1. Organs & body become more complex.
2. "Finishing Touches" (toenails, eyelids)
3. Appearance of bone

Characteristics of Embyronic Stage

1. Organs & major body systems develop rapidly.
- Respiratory, Digestive, Nervous
2. Risk of spontaneous abortion, or miscarriage.

When Birth Defects Occur

Embryonic Stage = Highest sensitivity to teratogens & defects

Stages of Prenatal Deveopment

1. Germinal (Conception to 2 wks).
2. Embryonic (2 to 8 wks)
3. Fetal (8wks to birth)

Prenatal Development

- Gestation
- Gestational age

- Obesity
- Intelligence, School achievement
- Personality, Temperament
- Schizophreni

Traits Influenced Heredity & Environment

Development reflects unique environment in which each child grows up.
- Accidents
- Illnesses
- Unique interactions with friends or peers

Adoption Studies

Adoption Studies

The degree to which adapted children resemble biological relatives or adopted family members.

The degree to which MZ & DZ twins resemble each other for a trait.

Twin Studies

Family Studies

The degree to which bio-relative share traits.

1. Family Studies
2. Adoption Studies
3. Twin Studies

Measuring Heritability

Genomics

Scientific study of the functions & interactions of various genes.

- Genomics
- Ethical & political issues?
- Genetic determinism
- Psychological impacts?
- Gene therapy

Genetic Testing

Karyotype

Shows chromosomal abnormalities.

Pseudohermaphroditism

Genitalia of one sex with some physical characteristics of the other sex are present.

Carrier

Individual unaffected by disorder but passes on gene to offspring.

Sex-linked Defects

Disorders linked to genes on sex chromosomes.
Affects males & females differently.
i.e. Red/green color blindness, hemophilia (common with males)

Epigenetic markers

May contribute to cancer, diabetes, or heart disease.
May change due environment factors.
- Imprinting.

Determination of Sex

Women also contributes the X.
Males determine whether baby will be a boy or not (Y).

Related Risks in the Rise in Multiple Birth Rate

1. Pregnancy complications
2. Premature delivery & lower birth weight.
3. Infant disability or death.
(Nowadays people postpone pregnancy for education)

Factors in the Rise in Multiple Birth Rate

1. Rising trend toward delaying childbirth.
2. Increasing use of fertility drugs.
(Stimulate more eggs @ the same time)

1. Monozygotic (MZ)
2. Dizygotic (DZ

Two Types of Multiple Births

zygote

one-celled organism resulting from fertilization

dizygotic twins

fraternal twins; twins conceived by the union of two different ova (or a single ovum that has split) with two different sperm cells; they are no more genetically alike than other siblings

monozygotic twins

identical twins; twins resulting from the division of a single zygote after fertilization; they are genetically similar

DNA

chemical that carried inherited instructions for the development of all cellular forms of life

genetic code

sequence of bases within the DNA molecule; governs the formation of proteins that determine the structure and functions of living cells

chromosomes

coils of DNA that consist of genes

genes

small segments of DNA located in definite positions on particular chromosomes; functional units of heredity

human genome

complete sequence of genes in the human body

autosomes

in humans, the 22 pairs of chromosomes not related to sexual expression

sex chromosomes

pair of chromosomes that determines sex: XX in the normal human female, XY in the normal human male

alleles

two or more alternative forms of a gene that occupy the same position on paired chromosomes and affect the same trait

homozygous

possessing two identical alleles for a trait

heterozygous

possessing differing alleles for a trait

dominant inheritance

pattern of inheritance in which, when a child receives different alleles, only the dominant one is expressed

recessive inheritance

pattern of inheritance in which a child receives identical recessive alleles, resulting in expression of a nondominant trait

polygenic influence

pattern of inheritance in which multiple genes at different sites on a chromosome affect a complex trait

mutations

permanent alterations in genes or chromosomes that may produce harmful characteristics

phenotype

observable characteristics of a person

genotype

genetic makeup of a person, containing both expressed and unexpressed characteristics

multifactorial transmission

combination of genetic and environmental factors to produce certain complex traits

epigenesis

mechanism that turns genes on or off and determines functions of body cells

incomplete dominance

pattern of inheritance in which a child receives two different alleles, resulting in partial expression of a trait

sex-linked inheritance

pattern of inheritance in which certain characteristics carried on the X-chromosome inherited from the mother are transmitted differently to her male and female offspring

down syndrome

chromosomal disorder characterized by moderate-to-severe mental retardation and by such physical signs as downward-sloping skin fold at the inner corners of the eyes. Also called trisomy-21

genetic counseling

clinical service that advises prospective parents of their probable risk of having children with hereditary defects

behavioral genetics

the study of relative hereditary and environmental influences on behavior

heritability

statistical estimate of contribution of heredity to individual differences in a specific trait within a given population

concordant

term describing tendency of twins to share the same trait or disorder

reaction range

potential variability, depending on environmental conditions, in the expression of a hereditary trait

canalization

limitation on variance of expression of certain inherited characteristics

genotype-environment interaction

the portion of of phenotypic variation that results from the reactions of genetically different individuals to similar environmental conditions

genotype-environment correlation

tendency of certain genetic and environmental influences to reinforce each other, may be passive, reactive (evocative), or active. Also called genotype-environment convariance

niche-picking

tendency of a person, especially after early childhood, to seek out environments compatible with his or her genotype

nonshared environmental effects

the unique environment in which each child grows up, consisting of distinctive influences or influences that affect one child differently that another

obesity

extreme overweight in relation to age, sex, height, and body type as defined by having a body mass index of above the 95th percentile

temperment

characteristic disposition, or style of approaching and reacting to situations

schizophrenia

mental disorder marked by loss of contact with reality; symptoms include hallucinations and delusions

gestation

period of development between conception and birth

gestational age

age of an unborn baby, usually dated from the first day of an expectant mother's last menstrual cycle

germinal stage

first 2 weeks of prenatal development, characterized by rapid cell division, blastocyst formation, and implantation in the wall of the uterus

embryonic stage

second stage of gestation (2 to 8 weeks), characterized by rapid growth and development of major body systems and organs

spontaneous abortion

natural expulsion from the uterus of an embryo that cannot survive outside the womb; also called miscarriage

fetal stage

final stage of gestation (from 8 weeks to birth), characterized by increased differentiation 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, so as to determine whether a pregnancy in progressing normally

teratogen

environmental agent, such as a virus, a drug, or radiation, that can interfere with normal prenatal development and cause developmental abnormalities

fetal alcohol syndrome (FAS)

combination of mental, motor, and developmental abnormalities affecting the offspring of some women who drink heavily during pregnancy

acquired immune deficiency syndrome (AIDS)

viral disease that undermines effective functioning of the immune system

stress

physical or psychological demands on a person or organism