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genome
a complete set of chromosomes
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genotype
the genetic composition of an organism
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phenotype
the observable appearance of an organism
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chromosome
the strand of DNA found within a nucleus of a cell
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DNA (Deoxyribonucleic Acid)
Molecules that compose chromosomes
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gene
a functional hereditary unit made up of dna that occupies a fixed location on a chromosone
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gene expression
the translation of the genotype into the phenotype of an organism
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allele
alternative version of a particular gene
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homozygous
having two identical alleles for a given gene
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heterozygous
having t wo different alleles for a given gene
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recessive allelea
gene that will reproduceits characteristic phenotype only when it occurs in a homozygous pair
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dominant allele
a gene that produces its phenotype regardless of wether its paired allele is heterozygous or homozygous
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imprinted gene
a gene of which only the mothers or the fathers copy is expressed but not both in the normal mendelian sense
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ribonucleic acid (RNA)
a molecule that is similar to DNA that participates in the translation of genetic sequences into proteins.
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codon
a sequence of three bases on the DNA molecule that encode one of 20 amino acids
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proteome
the set of proteins encoded by the genome
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meiosis
cell division in sexually reproducing organisms that reduces the number of chromosomes in half in the reproductive cells such as sperm eggs and spores.
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linkage
the characteristic of genes located adjacent to one another to be passed along as a group
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crossing over
a proccess occuring during meiosis in which chromosomes exchange equivalent segments of DNA material
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mutation
a heritable alteration of genes
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sex linked characteristics
phenotypical characteristics that result from expression of genes on the x chromosome that are not duplicated on the y-chromosome.
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x chromosome inactivation
the pprocess by which one X chromosome in each female cell is silenced to equalize the amount of proteins procuced by males and femalse
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single nucleotide polymorphism (SNP)
variation that occurs in a gene when a single based is changed from one version to the next
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alzheimer's disease
a degenative, ultimately fatal condition marked initially by memory loss.
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zygote
the cell formed by the two merged reproductive cells
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embryo
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
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fetus
the unborn offspring; used to refer in humas to the developing individual following the embryonic stage until birth
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germ layer
one of the first three layers (endoderm, mesodem and ectoderm) that differintiate in the developing embryo
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ectoderm
one of the initial three germ layers of the embryo the source of the skin and neural tissue
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mesoderm
one of the initial three germ layers the embryo that will form connective tissue such as ligaments, muscles, blood vessels, and the urogenital systems
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endoderm
one of the initial three germ layers of the embryo that source of many internal organs
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neural plate
a layer formed by the differentiating neural cells within the embryonic ectoderm
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inducing factor
a chemical that produces celll differentiation
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neural tube
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.
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ventricular zone
the layer of cells within the lining of the neural tube that give rise to the new neural cells
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progenitor cell
a stem cell in the ventricular layer that gives rise to either additional progenitor cells or migrating neural cells
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mitosis
the process of a cell division that produces two identical daughter cells
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radial glia
special glia that radiate from the ventricular layer to the outer edge of the cerebral cortex, serving as a pathway for migrating neurons.
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notochord
an embryonic mesodermic structure lying under the neural tube that will eventually develop into the spinal vertebrae
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growth cone
the swelling at the tip of a growing azon or dendrite that helps the branch reach its synaptic target
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filopodia
long, fingerlike extensions from growth cones of axons and dendrites
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lamellipodia
flat, sheetlike extensions from the core of growth cones located between the filopodia
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fasiculation
the process by which azonos growing in the same direction stick together
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cell adhesion molecule (CAM)
a molecule on the surface of a grwoing azon that promotes fasciculation
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apoptosis
programmed cell death
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nerve growth factor
the first identified neurotophin
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neurotrophin
substance released by target cells that contributes to the survival of presynaptic neurons
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cell death gene
a gene responsible for triggering the activity of capases leading to apoptosis
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caspase
an enxyme within a cell that cuts up DNA and produces cell death
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synaptic pruning
the process in which functional synapses are maintained and nonfucntional synapses are lost
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plasticity
the ability to change
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critical period
a segment of time during development in which a particular experience is influential and after which experience has little or no effect
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hebb synapse
a synapse strenghtened by simultaneous activity. Named after Donald hebb
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imprinting
the process by which baby animals, particularly birds, learn to follow their mother immediately upon seeing her after birth or hatching.
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anencephaly
a neural tube in which the rostral neural tube does not develop normally, resulting in incomplete formation of the brain and skul.
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spina bifidia
a neural tube defect in which the caudal part of the tube does not close properly
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down syndrome
an abnormal genetic condtiion resulting from a genotype with three copies of chromosome 21 responsiible for moderate mental retardation and a characteristic physical appearance
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fragile x syndrome
a heritable genetic disorder that produces cognitive and physical abnormalities
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phenylketonuria (PKU)
a heritable condition in which the individual does not produce enzymes necessary for the breakdown of phenylalanine; left untreated the condition producess mental retarrdation
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fetal alcohol syndrome
a set of physical and cognitive characteristics that result from maternal use of alcohol during pregnancy
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anterograde degeneration
the deterioration of the axon segment separated from the cell body by the damage to the axon
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thetrograde degeneration
the deterioration of postsynaptic cells in response to loss of input from damaged presynaptic neurons.
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nogo
a substance that normally prevents further sprouting by mature axons
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dementia
deterioration of cognitive abilities resulting from brain disorders.
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neurogenesis
the birth of new neural cells
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neurofibrrillary tangle
an abnormal internal structure of neurons found in cases of alzheimers disease
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tau
an intracellular protein responsible for maintaining the structure of microtubules; broken down in conditions such as alzheimers disease
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amyloid
a protein structure associated with the degeneration of tissue, such as in patients with alzheimers and other types of dimentia.
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