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Dominant Inheritance
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Pattern of inheritance in which, when a child receives different alleles, only the dominant one is expressed.
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Heterozygous
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Possessing differing alleles for a trait.
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Down Syndrome
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Chromosomal disorder characterized by moderate-to-severe mental retardation and by such physical signs as downward-sloping skin fold at inner corners of the eyes.
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Reaction Range
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Potential variability depending on environmental conditions, in the expression of a heredity trait.
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Deoxyribonucleic Acid (DNA)
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Chemical that carried inherited instructions for the development of all cellular forms of life.
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Assisted Reproductive Technology (ART)
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Methods used to achieve conception through artificial means.
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Genotype-Environment Correlation
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Tendency of certain genetic and environmental influences to reinforce each other; may be passive, reactive (evocative), or active.
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Nonshared Environmental Effects
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The unique environment in which each child grows up, consisting of distinctive influences or influences that affect one child differently than another.
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Schizophrenia
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Neurological disorder marked by loss of contact with reality; hallucinations and delusions; loss of coherent, logical thought; and inappropriate emotionality.
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Autosomes
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In humans, the 22 pairs of chromosomes not related to sexual expression.
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Genes
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Small segments of DNA located in definite positions on particular chromosomes; functional units of heredity.
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Behavioral Genetics
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Quantitative study of relative heredity and environmental influences on behavior.
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Fertilization
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Union of sperm and ovum to produce a zygote; also called conception.
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Genotype
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Genetic makeup of a person, containing both expressed and unexpressed characteristics.
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Homozygous
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Possessing two identical alleles for a trait.
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Genetic Counseling
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Clinical service that advises prospective parents of their probably risk of having children with genetic defects.
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Alleles
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Two or more alternative forms of a gene that can occupy the same position on paired chromosomes and affect the same trait.
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Polygenic Inheritance
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Pattern of inheritance in which multiple genes at different sites on chromosomes affect a complex trait.
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Zygote
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One-cell organism resulting from fertilization.
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Sex-Linked Inheritance
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Pattern of inheritance in which certain characteristics carried on the X chromosomes inherited from the mother are transmitted differently to her male and female offspring.
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Temperament
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Characteristic disposition, or style of approaching and reacting to situations.
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Concordant
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Term describing the tendency of twins to share the same trait or disorder.
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Canalization
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Limitation on variance of expression of certain inherited characteristics.
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Mutations
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Permanent alterations in genes or chromosomes that usually produce harmful characteristics.
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Obesity
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Extreme overweight in relation to age, sex, heigh, and body type.
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Phenotype
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Observable characteristics of a person.
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Multifactorial Transmission
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Combination of genetic and environmental factors to produce certain complex traits.
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Sex Chromosomes
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Pair of chromosomes that determines sex, XX in a normal female, XY in a normal male.
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Genetic Code
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Sequence of bases within the DNA molecule; a set of rules that govern the formation of proteins that determine the structure and functions of living cells.
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Infertility
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Inability to conceive after 12 months of trying.
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Recessive Inheritance
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Pattern of inheritance in which a child receives identical recessive alleles, resulting in expression of a nondominant trait.
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Epigenises
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Mechanism that turns genes on or off and determines functions of body cells.
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Heritability
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Statistical estimate of contribution of heredity to individual differences in a specific trait within a given population at a particular time.
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Incomplete Dominance
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Pattern of inheritance in which a child receives two different alleles, resulting in partial expression of a trait.
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Chromosomes
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Coils of DNA that consists of genes.
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Human Genome
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The complete sequence of genes in the human body.
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