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Chapter 3 Terms

Fertilization Union of sperm and ovum to produce a zygote; also called conception
Zygote One-celled organism resulting from fertilization
Dizygotic 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; they are no more alike genetically then any other siblings
Monozygotic Twins Twins resulting from the division of a single zygote after fertilization, also called identical twin; they are genetically similar
Deoxyribonucleic Acid (DNA) Chemical that carries inherited instructions for the development of all cellular forms of life
Genetic Code Sequence of bases within the DNA molecule; governs the formation of proteins that determine the structure and functions of living cells
Chromosomes Coils of DNA that consist of genes
Genes Small segments of DNA located in definite positions on particular chromosomes; functional units of heredity
Human Genome Complete Sequence of genes in the human body
Mutation Permanent alterations in genes or chromosomes that may produce harmful characteristics
Autosomes In humans, the 22 pairs of chromosomes not related to sexual expression
Sex Chromosomes Pair of chromosomes that determines sex; XX in the normal human female; XY in the normal human male
Alleles Two or more alternative forms of a gene that occupy the same position on paired chromosomes and affect the same trait
Homozygous Possessing two identical alleles for a trait
Heterozygous Possessing differing alleles for a trait
Dominant Inheritance Pattern of inheritance in which when a child receives different alleles, only the dominant one is expressed
Recessive Inheritance Pattern of inheritance in which a child receives identical recessive alleles resulting in expression of non-dominant trait
Polygenic Inheritance Pattern of inheritance in which multiple genes at different sites on chromosomes affect a complex trait
Phenotype Observable characteristics of a person
Genotype Genetic makeup of a person, containing both expressed and unexpressed characteristics
Multifactorial Transmission Combination of genetic and environmental factors to produce certain complex traits
Epigenesis Mechanism that turns genes on or off and determines functions of body cells
Incomplete Dominance Pattern of inheritance in which a child receives two different alleles, resulting in partial expression of a trait
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
Down Syndrome Chromosomal disorder characterized by moderate-to-severe mental retardation and by such physical signs as a downward sloping skin fold at the inner corners of the eyes, also called trisomy
Genetic Counseling Clinical service that advises prospective parents of their probable risk of having children with hereditary defects
Behavioral Genetics Quantitative study of relative hereditary and environmental influences on behavior
Heritability Statistical estimate of contribution of heredity to individual differences in a specific trait within a given population
Concordant Term describing tendency of twins to share the same trait or disorder
Reaction Range Potential variability, depending on environmental conditions, in the expression of hereditary trait
Canalization Limitation on variance of expression of certain inherited characteristics
Genotype-environment Interaction The portion of phenotypic variation that results from the reactions of genetically different individuals to similar environmental conditions
Genotype-environment Correlation Tendency of certain genetic and environmental influences to reinforce each other, amy be passive, reactive (evocative), or active. Also called genotype-environment covariance.
Niche-Picking 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 as defined by having a body mass index at or above the 95th percentile
Non-shared Environmental Effects The unique environment in which each child grows up, consisting of distinctive influences of influences that affect one child differently than another
Temperament Characteristic disposition, or style of approaching and reacting to situations
Schizophrenia Mental disorder marked by loss of contact with reality; symptoms include hallucinations and delusions
Gestation Period of development between conception and birth
Gestation Age Age of an unborn baby, usually dated from the first day of an expectant mothers last menstrual cycle
Germinal Stage First two weeks of prenatal development, characterized by rapid cell division blastocyst formation, and implantation in the wall of the uterus
Implantation The attachment of the blastocyst to the uterine wall, occurring at about day 6
Embryonic Stage Second stage of gestation (2 to 8 weeks), characterized by rapid growth and development of major body systems and organs
Spontaneous Abortion Natural expulsion from the uterus of an embryo that cannot survive outside the womb; also called miscarriage
Fetal Stage Final stage of gestation(from 8 weeks to birth), characterized by increased differentiation of body parts and greatly enlarged body size
Ultrasound Prenatal medical procedure using high-frequency sound waves to detect the outline of a fetus and its movements, so as to determine whether a pregnancy is processing normally
Teratogen Environmental agent, scubas a virus, a drug, or radiation, that can interfere with normal prenatal development and cause developmental abnormalities
Fetal Alcohol Syndrome (FAS) Combination of mental, motor, and developmental abnormalities affecting the offspring of some women who drink heavily during pregnancy
Acquired Immune Deficiency Syndrome (AIDS) Viral disease that undermines effective functioning of the immune system
Stress Physical or psychological demands on a person or organism
Created by: boconnor13