chapter 5

a complete set of chromosomes 

the genetic composition of an organism 

the observable appearance of an organism

the strand of DNA found within a nucleus of a cell

Molecules that compose chromosomes

a functional hereditary unit made up of dna that occupies a fixed location on a chromosone

the translation of the genotype into the phenotype of an organism

alternative version of a particular gene

having two identical alleles for a given gene

having t wo different alleles for a given gene

gene that will reproduceits characteristic phenotype only when it occurs in a homozygous pair

a gene that produces its phenotype regardless of wether its paired allele is heterozygous or homozygous

a gene of which only the mothers or the fathers copy is expressed but not both in the normal mendelian sense

a molecule that is similar to DNA that participates in the translation of genetic sequences into proteins.

a sequence of three bases on the DNA molecule that encode one of 20 amino acids

the set of proteins encoded by the genome

cell division in sexually reproducing organisms that reduces the number of chromosomes in half in the reproductive cells such as sperm eggs and spores.

the characteristic of genes located adjacent to one another to be passed along as a group

a proccess occuring during meiosis in which chromosomes exchange equivalent segments of DNA material

a heritable alteration of genes

phenotypical characteristics that result from expression of genes on the x chromosome that are not duplicated on the y-chromosome.

the pprocess by which one X chromosome in each female cell is silenced to equalize the amount of proteins procuced by males and femalse

variation that occurs in a gene when  a single based is changed from one version to the next

a degenative, ultimately fatal condition marked initially by memory loss.

the cell formed by the two merged reproductive cells

an organism in its early stage of development; in humans, the developing individual is reffered to as an embryo between two and eight weeks following conception

the unborn offspring; used to refer in humas to the developing individual following the embryonic stage until birth 

one of the first three layers (endoderm, mesodem and ectoderm) that differintiate in the developing embryo 

one of the initial three germ layers of the embryo the source of the skin and neural tissue

one of the initial three germ layers the embryo that will form connective tissue such as ligaments, muscles, blood vessels, and the urogenital systems

one of the initial three germ layers of the embryo that source of many internal organs

a layer formed by the differentiating neural cells within the embryonic ectoderm

a chemical that produces celll differentiation

a structure formed by the developing embryonic neural plate that will eventually form the brain and spinal cord, with the interior of the tube forming the ventricle system of the adult brain.

the layer of cells within the lining of the neural tube that give rise to the new neural cells

a stem cell in the ventricular layer that gives rise to either additional progenitor cells or migrating neural cells

the process of a cell division that produces two identical daughter cells

special glia that radiate from the ventricular layer to the outer edge of the cerebral cortex, serving as a pathway for migrating neurons.

an embryonic mesodermic structure lying under the neural tube that will eventually develop into the spinal vertebrae

the swelling at the tip of a growing azon or dendrite that helps the branch reach its synaptic target

long, fingerlike extensions from growth cones of axons and dendrites

flat, sheetlike extensions from the core of growth cones located between the filopodia

the process by which azonos growing in the same direction stick together

a molecule on the surface of a grwoing azon that promotes fasciculation

programmed cell death

the first identified neurotophin

substance released by target cells that contributes to the survival of presynaptic neurons

a gene responsible for triggering the activity of capases leading to apoptosis

an enxyme within a cell that cuts up DNA and produces cell death

the process in which functional synapses are maintained and nonfucntional synapses are lost

the ability to change

a segment of time during development in which a particular experience is influential and after which experience has little or no effect

a synapse strenghtened by simultaneous activity. Named after Donald hebb

the process by which baby animals, particularly birds, learn to follow their mother immediately upon seeing her after birth or hatching.

a neural tube in which the rostral neural tube does not develop normally, resulting in incomplete formation of the brain and skul.

a neural tube defect in which the caudal part of the tube does not close properly

an abnormal genetic condtiion resulting from a genotype with three copies of chromosome 21 responsiible for moderate mental retardation and a characteristic physical appearance

a heritable genetic disorder that produces cognitive and physical abnormalities

a heritable condition in which the individual does not produce enzymes necessary for the breakdown of phenylalanine; left untreated the condition producess mental retarrdation

a set of physical and cognitive characteristics that result from maternal use of alcohol during pregnancy

the deterioration of the axon segment separated from the cell body by the damage to the axon

the deterioration of postsynaptic cells in response to loss of input from damaged presynaptic neurons.

a substance that normally prevents further sprouting by mature axons

deterioration of cognitive abilities resulting from brain disorders.

the birth of new neural cells

an abnormal internal structure of neurons found in cases of alzheimers disease

an intracellular protein responsible for maintaining the structure of microtubules; broken down in conditions such as alzheimers disease

a protein structure associated with the degeneration of tissue, such as in patients with alzheimers and other types of dimentia.