| A | B |
|---|
| DNA (deoxyribonucleic acid) | The molecule that contains the chemical instructions for cells to manufacture various proteins. |
| chromosome | One of the 46 molecules of DNA (in 23 pairs) that each cell of the human body contains and that, together, contain all the genes. |
| gamete | A reproductive cell; that is, a sperm or an ovum that can produce a new individual if it combines with a gamete from the other sex to form a zygote. |
| zygote | The single cell that is formed from the fusing of two gametes, a sperm and an ovum. |
| gene | A section of a chromosome and the basic unit for the transmission of heredity, consisting of a string of chemicals that are instructions for the cell to manufacture certain proteins. |
| geneotype | An organism's entire genetic inheritance, or genetic potential. |
| phenotype | The observable characteristic of a person, including appearance, personality, intelligence, and all other traits. |
| allele | Any of the possible forms in which a gene for a particular trait can occur. |
| genome | The full set of genes that are the instructions to make an individual member of a certain species. |
| monozygotic twins | Twins who originate from one zygote that splits apart very early in development. |
| dizygotic twins | Twins who are formed when two separate ova are fertilized by two separate sperm at roughly the same time. |
| XX | A 23rd chromosome pair that consists of two X-shaped chromosomes, one each from the mother and the father. XX zygotes become females. |
| XY | A 23rd chromosome pair that consists of an X-shaped chromosome from the mother and a Y-shaped chromosome from the father. XY zygotes become males. |
| polygenic | Referring to a trait that is influenced by many genes. |
| multifactorial | Referring to a trait that is affected by many factors, both genetic and environmental. |
| regulator gene | A gene that directs the interactions of other genes, controlling their expression, duplication, and transcription. |
| additive gene | A gene that adds something to some aspect of the phenotype. Its contribution depends on additions from the other genes, which may come from either the same or the other parent. |
| dominant-recessive pattern | The interaction of a pair of alleles in such a way that the phenotype reveals the influence of one allele (the dominant gene more than that of the other (the recessive gene). |
| carrier | A person whose genotype includes a gene that is not expressed in the phenotype. |
| heritability | A statistic that indicates what percent-age of the variation in a particular trait within a particular population, in a particular context and era, can be traced to genes. |
| down syndrome | A condition in which a person has 47 chromosomes instead of the usual 46, with three rather than two chromosomes at the 21st position. |
| fragile X syndrome | A genetic disorder in which part of the X chromosome seems to be attached to the rest of it by a very thin string of molecules. |
| genetic counseling | Consultation and testing by trained experts that enable individuals to learn about their genetic heritage, including harmful conditions that they might pass along to any children they conceive |
| phenylketonuria (PKU) | A genetic disorder in which a child's body is unable to metabolize an amino acid called phenylalanine. |
| germinal period | The first two weeks of prenatal development after conception, characterized by rapid cell division and the beginning of cell differentiation. |
| embryonic period | The stage of prenatal development from approximately the third through the eighth week after conception, during which the basic forms of all body structures, including internal organs, develop. |
| fetal period | The stage of prenatal development from the ninth week after conception until birth, during which the fetus grows in size and matures in functioning. |
| placenta | The organ that surrounds the developing embryo and fetus, sustaining life via the umbilical cord. |
| implantation | The process, beginning about 10 days after conception, in which the developing organism burrows into the placenta that lines the uterus, where it can be nourished and protected as it continues to develop. |
| embryo | The name for a developing human organism from about the third through the eighth week after conception. |
| fetus | The name for a developing human organism from the start of the ninth week after conception until birth. |
| sonogram | An image of an unborn fetus (or an internal organ) produced by scanning it with high-frequency sound waves. (Also called ultrasound) |
| age of viability | The age (about 22 weeks after conception) at which a fetus may survive outside the mother's uterus if specialized medical care is available. |
| Apgar scale | A quick assessment of a newborn's body functioning. |
| doula | A woman who helps with the birth process. |
| cesarean section (c-section) | A surgical birth, in which incisions through the mother's abdomen and uterus allow the fetus to be removed quickly, instead of being delivered through the vagina. |
| low birthweight (LBW) | A body weight at birth of less than 5 1/2 pounds (2,500 grams). |
| very low birthweight (VLBW) | A body weight at birth of less than 3 pounds, 5 ounces (1,500 grams). |
| extremely low birthweight (ELBW) | A body weight at birth of less than 2 pounds, 3 ounces (1,000 grams). |
| preterm birth | A birth that occurs 3 or more weeks before the full 38 weeks of the typical pregnancy have elapsed--that is, at 35 or fewer weeks after conception. |
| small for gestational age (SGA) | Having a body weight at birth that is significantly lower than expected, given the time since conception. |
| kangaroo care | A child-care technique in which the mother of a low-birthweight infant holds the baby between her breasts like a kangaroo that carries her immature newborn in a pouch on her abdomen. |
| postpartum depression | The sadness and inadequacy felt by some new mothers in the days and weeks after giving birth |
| parent-infant bond | The strong, loving connection that forms as parents hold, examine, and feed their newborn. |
| fetal alcohol syndrome (FAS) | A cluster of birth defects, including abnormal facial characteristics, slow physical growth, and retarded mental development, that may occur in the child of a woman who drinks alcohol while pregnant. |
| teratogens | Agents and conditions, including viruses, drugs, and chemicals, that can impair prenatal development and result in birth defects or even death. |
| threshold effect | A situation in which a certian teratogen is relatively harmless in small doses but becomes harmful once exposure reaches a certain level (the threshold) |
