Chromosome- a thread-like structure made up of genes.
Genes- The segments on a DNA molecule that act as hereditary blueprints for the organism's development.
Deoxyribonucleic acid (DNA)- A long double-stranded molecule that makes up chromosomes.Haploid or germ cell- the sperm or the ovum that contains 23 chromosomes.
Diploid cell-the cell that is formed by the union of two haploid cells and is made up of 46 chromosomes in the human zygote.
Human Zygote- the cell that is formed by the union of the sperm and ovum.
Mitosis- the process of cell duplication and division that generates all the individual's cell except for the germ cells.
Meiosis- the cell division process that forms the germ cells.
Genotype- the genetic endowment of an individual. The particular gene forms that the individual has inherited.
Phenotype- the observable characteristics of an individual.
Allele- an alternate form of a gene coded for a particular trait.
Homozygous- having inherited two genes of the same allelic form for a trait.
Heterozygous- having inherited two genes of different allelic form for a trait.
Dominant allele- The allele that is expressed when an individual possesses two different alleles for the same trait.
Recessive allele- the allele that is not expressed when an individual possesses two different alleles for the same trait.
Codominance- a trait that is determined by two alleles but is different from the trait produced by either of the contributing alleles alone.
Sex-linked characteristics- traits determined by genes that are found on only the X or the Y chromosome.
neuron - the basic operative unit of brain activity - the nerve cell.
axon - the main protruding branch of a neuron that carries messages to other cells in the form of electrical impulses.
dendrite - the protruding part of a neuron that receives messages from the axons of other cells.
synapse - the tiny gap between axons and dendrites.
neurotransmitter - a chemical secreted by the cell sending a message that carries the impulse across the synaptic gap to the receiving cell.
myelin - a sheath of fatty cells that insulate axons and speeds transmission of nerve impulses from one neuron to the next.
cerebral cortex - the brain's outermost layer of the cerebrum which is divided into two hemispheres, each of which is divided into four lobes.
- occipital lobe - specialized for vision
- temporal lobe - specialized for hearing and speech
- frontal lobe - motor control of coordination of the functions of other cortical areas
- parietal lobe - spacial perception
spinal cord - the part of the CNS that extends from the waist to the base of the brain.
brain stem - the base of the brain which controls such elementary reactions as blinking and sucking, as well as such vital functions as breathing and sleeping
cerebellum - located between the brain stem and the rear of the cerebral cortex. Controls posture, balance, and coordination.
corpus collosum - a bundle of fibers that connects the left and right hemispheres and carries the messages needed to coordinate and integrate left and right brain functions.