Ch 5 Definitions: Genetics & the Development of the Human Brain Flashcards
genotype
the genetic composition of an individual organism
phenotype
the observable appearance of an individual organism
gene
a functional hereditary unit made up of DNA that occupies a fixed location on a chromosome
gene expression
the translation of the genotype into the phenotype of an organism
allele
alternative version of a particular gene
homozygous
having two identical alleles for a given gene
heterozygous
having two different alleles for a given gene
recessive allele
a gene that will produce its characteristic phenotype only when it occurs in a homozygous pair
dominant allele
a gene that produces its phenotype regardless of whether it occurs in a heterozygous or homozygous pair
meiosis
cell division that reduces the number of chromosomes in half in the reproductive cells
linkage
the characteristic of genes located adjacent to one another to be passed along as a group
crossing over
a process occurring during meiosis in which chromosomes exchange equivalent segments of DNA
mutation
a heritable alteration of genes
sex-linked characteristic
phenotypical characteristics that result from expression of genes on the X chromosome that are not duplicated on the Y chromosome
X chromosome inactivation
the process by which one X chromosome in each female cell is silenced to equalize the amount of proteins produced by males & females
single nucleotide polymorphism
variation between alleles involving a single base
copy-number variation (CNVs)
variations resulting from insertions, duplications, or deletions of sections of DNA
epigenetics
the reversible development of traits by factors that determine how genes perform
histone modification
changes in the structure of histones that make it more or less likely that a segment of DNA will be transcribed
DNA methylation
addition of a methyl group to a DNA molecule turns off the gene
gene silencing by non-coding RNA
regulation of gene expression by segments of RNA that are not translated into protein
RNA interference (RNAi)
inhibition of gene expression by non-coding RNA molecules that disable messenger RNA
zygote
the cell formed by two merged reproductive cells
embryo
in humans, the developing individual between the 2nd & 8th week following conception
fetus
the developing organism between the embryonic stage & birth
ectoderm
the germ layer that develops into the nervous system, skin, and hair
mesoderm
the germ layer that develops into connective tissue, muscle, blood vessels, bone, and the urogenital systems
endoderm
the germ layer that develops into internal organs including the stomach & intestines
neural plate
a layer formed by differentiating neural cells within the ectoderm of the embryo
neural tube
a structure formed by the embryonic neural plate that will develop into the brain & spinal cord
prosencephalon
one of the three early divisions of the neural tube that will develop into the forebrain
mesencephalon
one of the three early divisions of the neural tube that will develop into the midbrain
irhombencephalon
one of the three early divisions of the neural tube that will develop into the hindbrain
diencephalon
a division of the prosencephalon that will contain the thalamus, hypothalamus, and retina of they eye
telencephalon
a division of the prosencephalon that develops into the bulk of the cerebral hemispheres
myelencephalon
a division of the rhombencephalon that develops into the medulla
metencephalon
a division of the rhombencephalon that develops into the pons & cerebellum
neurogenesis
the birth of new neurons & glia
migration
the movement of cells to their mature location
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
aggregation
a process in which cells join others to form structures in the nervous system
differentiation
the development of stem cells into more specific types of cells
differentiation-inducing factor (DIFs)
chemicals that stimulate changes in cell chemistry that produce cellular differentiation
neurite
an immature projection from a neuron
growth cone
the swelling at the tip pf a growing axon or dendrite that helps the branch reach its synaptic target
filopodia
long, fingerlike extensions from a growth cone
lamellipodia
flat, sheetlike extensions from the core of a growth cone
synaptic specificity
the process by which a neurite identifies appropriate postsynaptic target cells from the many cells in the vicinity
apoptosis
programmed cell death
neurotrophin
substance released by target cells that contributes to the survival of presynaptic neurons
synaptic pruning
the process in which functional synapses are maintained & nonfunctional synapses degenerate
critical period
a period of time during development in which experience is influential & after which experience has little to no effect
anencephaly
defect in the rostral closure of the neural tube resulting in incomplete development of bran & skull
spina bifida
defect in caudal neural tube closure that results in mobility problems
Down syndrome
a condition associated with moderate intellectual disability resulting from having 3 full or partial copies of chromosome 21; also known as trisomy 21
fragile X syndrome
a heritable sex-linked genetic disorder that produces physical & social deficits
phenylketonuria
a heritable condition characterized by the inability to metabolize phenylalanine
fetal alcohol syndrome
a set of physical & cognitive characteristics that result from maternal use of alcohol during pregnancy
multiple reserve hypothesis
the resources a person possesses that offset age-related reductions in functioning
