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21 Cards in this Set

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How does conception normally occur?
Fertilization, the union of an ovum and a sperm, results in the formation of a one-celled zygote, which then duplicates itself by cell division. most likely to occur on day of ovulation or 5 days before, while ovum is passing through fallopian tube.
By what two ways can multiple births occur?
fertilization of two ova (or one ovum that has split)

by the splitting of one fertilized ovum
Define dizygotic twins.
"of two eggs" "fraternal". different genetic makeups and may be of different sexes
Define monozygotic twins.
"of one egg." "identical" same genetic makeup. Because of differences in prenatal and postnatal experience, may differ in temperament and other respects.
Define genes, DNA, genetic code, chromosomes, and the human genome.
The basic functional units of heredity are the genes and are small segments of DNA located by function in a definite position on a particular chromosome.

DNA carries the biochemical instructions, or genetic code(sequence of base pairs within DNA which determine inherited characteristics), for the formation and function of body cells.

Chromosomes are coils of DNA that carry the genes.

The complete sequence or mapping of genes in the human body and their locations is the human genome.
How many pairs of chromosomes does a normal human have? Which pair determines sex?
At conception, each normal human being receives 23 chromosomes from the mother and 23 from the father. These form 23 pairs of chromosomes---22 pairs of autosomes and 1 pair of sex chromosomes. A child who receives an X chromosome from each parent will be a female. If the child receives a Y chromosome from the father, a male will be conceived.
Explain dominant and recessive inheritance, codominance, and homo/heterozygous.
The simplest patterns of genetic transmission are dominant and recessive inheritance. Dominant inheritance is when a child receives contradictory alleles(paired genes that affect a trait) and only the dominant one is expressed. Recessive is when a child receives identical recessive alleles, resulting in expression of a nondominant trait. Sometimes codominance, when neither of two alleles is dominant and the resulting trait reflects the influence of both, occurs. When a pair of alleles are the same, a person is homozygous for the trait; when they are different, the person is heterozygous.
Define multifactorial transmission/polygenic inheritance, phenotype and genotype.
Most normal human characteristics are the result of polygenic or multifactorial transmission. Polygenic is when multiple genes affect a complex trait. Multifactorial is the combination of genetic and environmental factors to produce certain complex traits. Except for monozygotic twins, each child inherits a unique genotype. Dominant inheritance and multifactorial transmission explain why a person's phenotype(observable characteristics) does not always express the underlying genetic makeup or genotype.
Birth defects and diseases may result from...?
Birth defects and diseases may result from simple dominant, recessive, or sex-linked inheritance(certain characteristics carried on the X chromosome inherited from the mother are transmitted differently to her male and female offspring), from mutations(permanent alterations in genes or chromosomes that may produce harmful characteristics), or from genome imprinting. Chromosomal abnormalities also can cause birth defects. Incomplete dominance--partial expression of a trait.
How are heredity and environment influences studied scientifically?
Research in behavioral genetics(quantitative study of relative hereditary and environmental influences) is based on the assumption that the relative influences of heredity and environment can be measured statistically. If heredity is an important influence on a trait, genetically closer persons will be more similar in that trait. Family studies, adoption studies, and studies of twins enable researchers to measure the heritability(statistical estimate of contribution of heredity to individual differences in a specific trait within a given population) of specific traits.
Define the concepts of reaction range, canalization, genotype-environment interaction, genotype-environment correlation (or covariance), and niche-picking
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--portion of the phenotypic variation that results from the reactions of genetaically different individuals to similar environmental conditions.
genotype-environment correlation--tendency of cerain genetic and environmental influeces to reinforce each other, may be passive(musical parents=musical child), reactive(nonmusical parents nurture musically interested child, or active(niche-picking).
niche-picking--tendency of a person, especially after early childhood to seek out environments compatible with his or her genotype.
Siblings and heredity/environment?
Siblings tend to be more different than alike in intelligence and personality. According to behavior genetics research, heredity accounts for most of the similarity, and nonshared environmental effects account for most of the difference. Critics claim that this research, for methodological reasons, minimizes the role of parenting and the complexity of developmental systems.
Conditions influences by both heredity/environment?
Obesity, longevity, intelligence, and temperament are influenced by both heredity and environment.
Schizophrenia(mental disorder marked by loss of contact with reality, symptoms include hallucinations and delusions) and autism(pervasive developmental disorder of the brain characterized by lack of normal social interaction, impaired communication and imagination, and a highly restricted range of abilities and interests) are psychopathological disorders influenced by both heredity and environment.
3 stages of prenatal development/what happens in each?
Prenatal development occurs in three stages of gestation: the germinal(fertilization to 2 weeks, characterized by rapid cell division, increasing complexity and differentiation, and implantation in uterine wall), embryonic(2-8 weeks, rapid growth and dev of major body systems and organs), and fetal(8 weeks to birth,increased detail of body parts and greatly enlarged body size) stages.
Growth and development both before and after birth follow the cephalocaudal principle (head to tail) and the proximodistal principle (center outward).
Severely defective embryos usually are spontaneously aborted during the first trimester of pregnancy.
What can fetuses do?
As fetuses grow, they move less, but more vigorously. Swallowing amniotic fluid, which contains substances from the mother's body, stimulates taste and smell. Fetuses seem able to hear, exercise sensory discrimination, learn, and remember.
What environmental influences can affect prenatal development?
The developing organism can be greatly affected by its prenatal environment. The likelihood of a birth defect may depend on the timing and intensity of an environmental event and its interaction with genetic factors.
Important environmental influences involving the mother include nutrition, physical activity, smoking, intake of alcohol or other drugs, transmission of maternal illnesses or infections, maternal age, and external environmental hazards, such as chemicals and radiation. External influences also may affect the father's sperm.
What techniques can assess a fetus' health and well-being, and what is the importance of prenatal care?
Ultrasound(high frequency sound waves to detect outline of fetus and its movements), amniocentesis(sample of amniotic fluid withdrawn and analyzed to detect presence of certain genetic or multifactorial defects/chromosomal disorders. rec for women 35+), chorionic villus sampling(tissue from ends of hairlike projections of the chorion(membrane surrounding fetus)tested. can be performed 8-13 wks. 5% greater chance of miscarriage), embryoscopy(insertion of tiny viewing scope into abdomen--6 wks), preimplantation genetic diagnosis(IVF embryos), umbilical cord sampling, and maternal blood tests can be used to determine whether an unborn baby is developing normally.
Early, high-quality prenatal care is essential for healthy development. It can lead to detection of defects and disorders and, especially if begun early and targeted to the needs of at-risk women, may help reduce maternal and infant death, low birthweight, and other birth complications.
Describe ovulation.
Small sac surrounding ovum(follicle) matures in either ovary and results in expulsion of the ovum. Ovum is swept along the fallopian tube by cilia toward the uterus.
Define Down syndrome.
most common chromosomal disorder characterized by moderate to severe mental retardation and by such physical signs as a downward sloping skin fold at the inner corner of the eyes. also called trisomy-21, caused by extra 21st chromosome or the translocation of part of the 21st chromosome onto another chromosome.
Define embryonic disk, ectoderm, endoderm, and mesoderm.
Embryonic disk--thickened cell mass from which the embryo begins to develop.
Ectoderm--upper layer of disk--will become outer layer of skin, hair, nails, teeth, sensory organs, and nervous system.
Endoderm--lower layer, will become digstive system, liver, pancreas, salivary glands, respiratory system.
Mesoderm--middle layer, inner layer of skin, muscles, skeleton, excretory, circulatory.
Describe fetal alcohol syndrome.
slow prenatal/postnatal growth, facial and bodily malformations, disorders of the CNS.