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Child Development - A Thematic Approach
, Fifth Edition
Danuta Bukatko - College of the Holy Cross
Marvin W. Daehler - University of Massachusetts, Amherst
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| | Glossary Terms
A | B |
C | D | E |
F | G | H |
I | J | K |
L | M | N |
O | P | Q |
R | S | T |
U | V | W |
X | Y | Z
Allele
Alternate form of a specific gene; provides a genetic basis for many individual differences.
Amniocentesis
Method of sampling the fluid surrounding the developing fetus by insertion of a needle. Used to diagnose fetal genetic and developmental disorders.
Autosomes
Twenty-two pairs of homologous chromosomes. The two members of each pair are similar in size, shape, and genetic function. The two sex chromosomes are excluded from this class.
Behavior genetics
Study of how characteristics and behaviors of individuals, such as intelligence and personality, are influenced by the interaction between genotype and experience.
Canalization
Concept that the development of some attributes is governed primarily by the genotype and only extreme environmental conditions will alter the phenotypic pattern for these attributes.
Chorionic villus sampling
Method of sampling fetal chorionic cells. Used to diagnose embryonic genetic and developmental disorders.
Chromosomes
Threadlike structures of DNA, located in the nucleus of cells, that form a collection of genes. A human body cell normally contains forty-six chromosomes.
Codominance
Condition in which individual, unblended characteristics of two alleles are reflected in the phenotype.
Concordance rate
Percentage of pairs of twins in which both members have a specific trait identified in one twin.
Crossing over
Process during the first stage of meiosis when genetic material is exchanged between autosomes.
Deoxyribonucleic acid (DNA)
Long, spiral staircaselike sequence of molecules created by nucleotides identified with the blueprint for genetic inheritance.
Dominant allele
Allele whose characteristics are reflected in the phenotype even when part of a heterozygous genotype. Its genetic characteristics tend to mask the characteristics of other alleles.
Fetal blood sampling
Method of withdrawing blood from the umbilical cord of the fetus. Used to diagnose genetic disorders, especially those that affect the blood.
Fragile X syndrome
Disorder associated with a pinched region of the X chromosome; a leading genetic cause of mental retardation in males.
Fraternal twins
Siblings who share the same womb at the same time but originate from two different eggs fertilized by two different sperm cells. Also called dizygotic twins.
Gametes
Sperm cells in males, egg cells in females, normally containing only twenty-three chromosomes.
Gene
Large segment of nucleotides within a chromosome that codes for the production of proteins and enzymes. These proteins and enzymes underlie traits and characteristics inherited from one generation to the next.
Genetic counseling
Medical and counseling specialty concerned with determining and communicating the likelihood that prospective parents will give birth to a baby with a genetic disorder.
Genetic screening
Systematic search using a variety of tests to detect individuals at developmental risk due to genetic anomalies.
Genomic imprinting
Instances of genetic transmission in which the expression of a gene is determined by whether the particular allelic form has been inherited from the mother or the father.
Genotype
Total genetic endowment inherited by an individual.
Heritability
Proportion of variability in the phenotype that is estimated to be accounted for by genetic influences within a known environmental range.
Heterozygous
Genotype in which two alleles of a gene are different. The effects on a trait will depend on how the two alleles interact.
Homozygous
Genotype in which two alleles of a gene are identical, thus having the same effects on a trait.
Human genome
Entire inventory of nucleotide base pairs that compose the genes and chromosomes of humans.
Identical twins
Two individuals who originate from a single zygote (one egg fertilized by one sperm), which early in cell division separates to form two separate cell masses. Also called monozygotic twins.
Karyotype
Pictorial representation of an individual’s chromosomes.
Maternal blood screening
Tests performed on a woman’s blood to determine if the fetus she is carrying has an increased risk for some types of chromosomal and metabolic disorders.
Meiosis
Process of cell division that forms the gametes; normally results in twenty-three chromosomes in each human egg and sperm cell rather than the full complement of forty-six chromosomes.
Mitosis
Process of cell division that takes place in most cells of the human body and results in a full complement of identical material in the forty-six chromosomes in each cell.
Mutation
Sudden change in molecular structure of a gene; may occur spontaneously or be caused by an environmental event such as radiation.
Niche picking
Tendency to actively select an environment compatible with a genotype.
Nucleotide
Repeating basic building block of DNA consisting of nitrogen-based molecules of adenine, thymine, cytosine, and guanine.
Phenotype
Observable and measurable characteristics and traits of an individual; a product of the interaction of the genotype with the environment.
Phenylketonuria (PKU)
Recessive genetic disorder in which phenylalanine, an amino acid, fails to be metabolized. Unless dietary changes are made to reduce intake of phenylalanine, severe mental retardation occurs.
Polygenic
Phenotypic characteristic influenced by two or more genes.
Range of reaction
Range of phenotypic differences possible as a result of different environments interacting with a specific genotype.
Recessive allele
Allele whose characteristics do not tend to be expressed when part of a heterozygous genotype. Its genetic characteristics tend to be masked by other alleles.
Sickle cell disease
Genetic blood disorder common in regions of Africa and other areas where malaria is found and among descendants of these regions. Abnormal blood cells carry insufficient oxygen.
Sickle cell trait
Symptoms shown by those possessing a heterozygous genotype for sickle cell anemia.
Trisomy
Condition in which an extra chromosome is present.
Ultrasonography
Method of using sound wave reflections to obtain a representation of the developing fetus. Used to estimate gestational age and detect fetal physical abnormalities.
Williams syndrome
Dominant genetic disorder involving the deletion of a set of genes that results in affected individuals typically having a strong social orientation, good musical ability, and some unusual capabilities; accompanied by mental retardation and severe deficits in numerical and spatial ability.
X chromosome
Larger of the two sex chromosomes associated with genetic determination of sex. Normally females have two X chromosomes and males only one.
Y chromosome
Smaller of the two sex chromosomes associated with genetic determination of sex. Normally males have one Y chromosome and females none.
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