411 Chapter 2

The single cell formed from separate sperm and egg cells at conception.

The cell released monthly from a woman's ovaries, which, if fertilized, forms the basics for the developing organism.

The tube between the ovary and the uterus down which the ovum travels to the uterus and in which conception usually occurs.

The female organ in which the embryo/fetus develops (popularly referred to as the womb).

The cells produced in a man's testes that may fertilize an ovum following intercourse.

The structures, arrayed in 23 pairs, within each cell in the body that contain genetic information. Each chromosome is made up of many segments called genes.

Sperm and ova . These cells, unlike all other cells of the body, contain only 23 chromosome rather than 23 pairs.

The chemical of which chromosomes are composed.

A uniquely coded segment of DNA in a chromosome that affects one or more specific body processes or developments.

Term describing the genetic pattern when the two genes in the pair at any given genetic locus both carry the same instructions.

Term describing the genetic pattern when the two genes in the pair at any given genetic locus both carry different instructions, such as a gene for blue eyes from one parent and a gene for brown eyes from the other parent.

The pattern of characteristics and developmental sequences mapped in the genes of any specific individual, which will be modified by individual experience into the phenotype.

The expression of a particular set of genetic information in a specific environmen; the observable result of the joint operation of genetic and environmental influences.

The pattern of genetic transmission in which a single dominant gene influences a person's phenotype, but an individual must have two recessive genes to express a recessive trait.

Any pattern of genetic transmission in which multiple genes contribute to the outcome, such as is presumed to occur for complex traits such as intelligence or temperament.

The pattern of genetic transmission in which both genes and environment influence the phenotype.

Children carried in the same pregnancy but who develop from two separately fertilized ova. They are no more alike genetically than other pairs of siblings.

Children carried in the same pregnancy but who develop from the same fertilized ova. They are genetic clones of each other.

The first stage of prenatal development, beginning at conception and ending at implanatation of the zygote in the uterus (approximately the first 2 weeks).

Name for the mass of cells from roughly 4 to 10 days after fertilization.

The name given to the developing organism during the period of prenatal development between about 2 weeks and 8 weeks after conception, beginning with implantation of the blastocyst in the uterine wall.

The second stage of prenatal development, from week 2 through week 8, when the embryo's organs form.

The sac, or bag filled with liquid in which the embryo/fetus floats during prenatal life.

The outer layer of cells of the blastocyst during prenatal development, from which both the placenta and umbilical cord are formed.

An organ that develops between the fetus and the wall of the uterus during gestation.

The cord connecting the embryo/fetus to the placenta, containing two arteries and one vein.

The name given to the developing organism from about about 8 weeks after conception until birth.

The third stage of prenatal development, from week 8 to birth, when growth and organ refinement take place.

The fetus's capacity for survival outside the womb.

The cells in the nervous system that are responsible for tramsmission and reception of nerve impulses.

The rapid development of neurons between the 10th and 18th week of gestation.

The movement of neurons to specialized regions of the birth.

 The part of the cell that contains the nucleus and in which all the cell's vital functions are carried out.

Tiny spaces across which neural impulses flow from one neuron to the next.

Tall-like extensions of neurons.

Branchlike protrusions from the cell bodies of neurons.

The "glue" that holds neurons together to give form to the structures of the nervous system.

Substances such as viruses and drugs or events that can cause birth defects.

A genetic anomaly in which every cell contains three copies of chromosome 21 rather than two. Children born with this genetic pattern have characteristic physical features and usually have mental retardation.

A pattern of abnormalities, including mental retradation and minor physical anomalies, often found in children born to alcoholic mothers.