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A Child's World: Infancy through Adolescence, 9/e
Diane E. Papalia, University of Wisconsin-Madison
Sally Wendkos Olds
Ruth Duskin Feldman

Forming a New Life

Glossary


alleles  paired genes (alike or different) that affect a trait.
autism  pervasive developmental disorder of the brain; characterized by lack of normal social interaction, impaired communication and imagination, and repetitive, obsessive behaviors.
autosomes  the 22 pairs of chromosomes not related to sexual expression.
behavioral genetics  quantitative study of relative hereditary and environmental influences.
canalization  limitation on variance of expression of certain inherited characteristics.
chromosomes  coils of DNA that carry the genes
clone  (verb) to make a genetic copy of an individual; (noun) a genetic copy of an individual
concordant  term describing twins who share the same trait or disorder.
deoxyribonucleic acid (DNA)  chemical that carries inherited instructions for the formation and function of body cells.
dizygotic(two-egg) twins  twins conceived by the union of two different ova (or a single ovum that has split) with two different sperm cells; also called fraternal twins.
dominant inheritance  pattern of inheritance in which, when a child receives contradictory alleles, only the dominant one is expressed.
down syndrome  chromosomal disorder characterized by moderate-to-severe mental retardation and a downward sloping skin fold at the inner corner of the eyes.
fertilization  union of sperm and ovum fuse to produce a zygote; also called conception
genes  small segments of DNA located in definite positions on particular chromosomes
genetic code  sequence of base pairs within DNA, which determine inherited characteristics.
genotype  genetic makeup of a person, containing both expressed and unexpressed characteristics.
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 covariance.
genotype-environment interaction  the portion of phenotypic variation that results from the reactions of genetically different individuals to similar environmental conditions.
heritability  statistical estimate of contribution of heredity to individual differences in a specific trait within a given population.
heterozygous  possessing differing alleles for a trait.
homozygous  possessing two identical alleles for a trait.
human genome  complete sequence or mapping of genes in the human body and their locations.
infertility  inability to conceive after 12 to 18 months of trying.
monozygotic (one-egg) twins  twins resulting from the division of a single zygote after fertilization; also called identical twins.
multifactorial transmission  combination of genetic and environmental factors to produce certain complex traits.
mutations  permanent alterations in genes or chromosomes that may produce harmful characteristics.
natural selection  according to Darwin's theory of evolution, process by which characteristics that promote survival of a species are reproduced in successive generations, and characteristics that do not promote survival die out.
niche picking  tendency of a person, especially after early childhood, to seek out environments compatible with his or her projects.
nonshared environmental effects  tendency of a person, especially after early childhood, to seek out environments compatible with his or her genotype.
obesity  extreme overweight in relation to age, sex, height, and body type; sometimes defined as having a mass body index (weight-for-height) at or above the 85th or 95th percentile of growth curves for children of the same age and sex.
phenotype  observable characteristics of a person.
quantitative trait loci (QLT)  interaction of multiple genes each with affects of varying size, to produce a complex trait.
reaction range  potential variability, depending on environmental conditions, in the expression of a hereditary trait.
recessive inheritance  pattern of inheritance in which a child receives identical recessive alleles, resulting in expression of a nondominant trait.
schizophrenia  mental disorder marked by loss of contact with reality; symptoms include hallucinations and delusions.
sex chromosomes  pair of chromosomes that determines sex XX in the normal female, XY in the normal male.
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.
temperament  characteristic disposition, or style of approaching and reacting to situations.
zygote  one-celled organism resulting from fertilization