genetics, environment, and development

• 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.
• 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.
• Mitosis

  the process in which a cell duplicates its chromosomes and then divides into two genetically identical daughter cells.
• INDEPENDENT ASSORTMENT - the principle that each pair of chromosomes segregates independently of all other chromosome pairs during meiosis.
• 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
• Selective Breeding Experiment - a method of studying genetic

  influences by determining whether traits can be bred in animals through selective mating
• 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.
• Canalization Principle - 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.
• genotype

  the genetic make up of an organism, representing the specific combination of genes and alleles it inherits from its parents
• phenotype

  the observable traits and characteristics of an organism, which results from the interaction between its genotype and the environment