Hereditary Influences on Development

Cards

genotype the genetic endowment that an individual inherits.
phenotype the ways in which a person's genotype is expressed in observable or measurable characteristics.
conception the moment of fertilization, when a sperm penetrates an ovum, forming a zygote.
zygote a single cell formed at conception from the union of a sperm and an ovum.
chromosome a threadlike structure made up of genes; in humans there are 46 chromosomes in the nucleus of each body cell.
genes hereditary blueprints for development that are transmitted unchanged from generation to generation.
deoxyribonucleic acid DNA long, double-stranded molecules that make up chromosomes.
mitosis the process in which a cell duplicates its chromosomes and then divides into two genetically identical daughter cells.
meiosis the process by which a germ cell divides, producing gametes (sperm or ova) that each contain half of the parent cell's original complement of chromosomes; in humans, the products of meiosis contain 23 chromosomes.
crossing-over a process in which genetic material is exchanged between pairs of chromosomes during meiosis.
independent assortment the principle that each pair of chromosomes segregates independently of all other chromosome pairs during meiosis.
monozygotic (identical) twins twins who develop from a single zygote that later divides to form two genetically identical individuals.
dizygotic (fraternal) twins twins that result when a mother releases two ova at roughly the same time and each is fertilized by a different sperm, producing two zygotes that are genetically different.
X chromosome the longer of the two sex chromosomes; normal females have two X chromosomes, whereas normal males have only one.
Y chromosome the shorter of the two sex chromosomes; normal males have one Y chromosome, whereas females have none.
alleles alternative forms of a gene that can appear at a particular site on a chromosome.
simple dominant-recessive inheritance a pattern of inheritance in which one allele dominates another so that only its phenotype is expressed.
dominant allele a relatively powerful gene that is expressed phenotypically and masks the effect of a less powerful gene.
recessive allele a less powerful gene that is not expressed phenotypically when paired with a dominant allele.
homozygous having inherited two alleles for an attribute that are identical in their effects.
heterozygous having inherited two alleles for an attribute that have different effects.
carrier a heterozygous individual who displays no sign of a recessive allele in his or her own phenotype but can pass this gene to offspring.
codominance condition in which two heterozygous but equally powerful alleles produce a phenotype in which both genes are fully and equally expressed.
sickle-cell anemia a genetic blood disease that causes red blood cells to assume an unusual sickle shape and to become inefficient at distributing oxygen.
sex-linked characteristic an attribute determined by a recessive gene that appears on the X chromosome; more likely to characterize males.
polygenic trait a characteristic that is influenced by the action of many genes rather than a single pair.
congenital defect a problem that is present (though not necessarily apparent) at birth; such defects may stem from genetic and prenatal influences or from complications of the birth process.
autosomes the 22 pairs of human chromosomes that are identical in males and females.
Down syndrome a chromosomal abnormality (also known as trisomy-21) caused by the presence of an extra 21st chromosome; people with this syndrome have a distinctive physical appearance and are moderately to severely retarded.
mutation a change in the chemical structure or arrangement of one or more genes that has the effect of producing a new phenotype.
genetic counseling a service designed to inform prospective parents about genetic diseases and to help them determine the likelihood that they would transmit such disorders to their children.
fragile-X syndrome abnormality of the X chromosome caused by a defective gene and associated with mild to severe mental retardation, particularly when the defective gene is passed from mother to child.
amniocentesis a method of extracting amniotic fluid from a pregnant woman so that fetal body cells within the fluid can be tested for chromosomal abnormalities and other genetic defects.
chorionic villus sampling (CVS) an alternative to amniocentesis in which fetal cells are extracted from the chorion for prenatal tests. CVS can be performed earlier in pregnancy than is possible with amniocentesis.
ultrasound method of detecting gross physical abnormalities by scanning the womb with sound waves, thereby producing a visual outline of fetus
phenylketonuria (PKU) a genetic disease in which the child is unable to metabolize phenylalanine; if left untreated, it soon causes hyperactivity and mental retardation.
germline gene therapy a procedure, not yet perfected or approved for use with humans, in which harmful genes would be repaired or replaced with healthy ones, thereby permanently correctly a genetic defect.
behavioral genetics behavioral the scientific study of how genotype interacts with environment to determine behavioral attributes such as intelligence, personality, and mental health.
heritability the amount of variability in a trait that is attributable to hereditary factors.
selective breeding experiment a method of studying genetic influences by determining whether traits can be bred in animals through selective mating.
kinship the extent to which two individuals have genes in common.
twin design study in which sets of twins that differ in zygosity (kinship) are compared to determine the heritability of an attribute.
adoption design study in which adoptees are compared with their biological relatives and their adoptive relatives to estimate the heritability of an attribute or attributes
concordance rate the percentage of cases in which a particular attribute is present for one member of a twin pair if it is present for the other.
heritability coefficient a numerical estimate, ranging from.00 to +1.00, of the amount of variation in an attribute that is due to hereditary factors.
nonshared environmental influence (NSE) an environmental influence that people living together do not share that should make these individuals different from one another.
shared environmental influence (SE) an environmental influence that people living together share that should make these individuals similar to one another.
introversion/extroversion the opposite poles of a personality dimension: introverts are shy, anxious around others, and tend to withdraw from social situations; extroverts are highly sociable and enjoy being with others.
empathic concern a measure of the extent to which an individual recognizes the needs of others and is concerned about their welfare
parent effects model model of family influences in which parents (particularly mothers) are believed to influence their children rather than vice versa.
child effects model model of family influences in which children are believed to influence their parents rather than vice versa.
transactional model model of family influences in which parent and child are believed to influence each other reciprocally.
schizophrenia a serious form of mental illness characterized by disturbances in logical thinking, emotional expression, and interpersonal behavior.
bipolar disorder a psychological disorder characterized by extreme fluctuations in mood.
neurotic disorder an irrational pattern of thinking or behavior that a person may use to contend with stress or to avoid anxiety.
canalization genetic restriction of phenotype to a small number of developmental outcomes; a highly canalized attribute is one for which genes channel development along predetermined pathways, so the environment has little effect on the phenotype that emerges.
range-of-reaction principle the idea that genotype sets limits on the range of possible phenotypes that a person might display in response to different environments.
passive genotype/environment correlations the notion that the rearing environments that biological parents provide are influenced by the parents' own genes, and hence are correlated with the child's own genotype.
evocative genotype/environment correlations the notion that our heritable attributes affect others' behavior toward us and thus influence the social environment in which development takes place.
active genotype/environment correlations the notion that our genotypes affect the types of environments that we prefer and seek out.