Chapter 4 Flashcards
Genes
units of heredity that maintain their structural identity from one generation to another.
Chromosomes
strands of genes that also come in pairs.
RNA
controls sequence of amino acids in a protein molecule.
dominant gene
shows a strong effect in either the homozygous or heterozygous condition.
homozygous
If you have the same genes on your two copies of some chromosome,
heterozygous
If you have an unmatched pair of genes
Four bases of DNA
adenine, guanine, cytosine, and thymine.
recessive gene
shows its effects only in the homozygous condition.
sex-linked genes
genes on the sex chromosomes (X and Y).
Red-green color deficiency
- a sex linked gene
- most common in men
sex-limited genes
present in both sexes but active mainly in one sex.
mutation
a heritable and permanent change in a DNA molecule.
epigenetics
deals with changes in gene expression.
Methylation
Adding a methyl group turns genes off.
Acetyl groups
An acetyl group loosens histone’s grip and increases gene activation.
monozygotic twins
- identical.
- have same genes.
dizygotic twins
- fraternal
candidate gene approach
examination of a single gene and it’s association with a behaviour based on theory.
genome wide association study
examine all genes and determine differences
between two groups with a particular behavior of interest.
phenylketonuria (PKU)
a genetic inability to metabolize the amino acid phenylalanine.
- can lead to mental retardation if not treated.
evolution
a change over generations in the frequencies of various genes in a population.
artificial selection
choose individuals with a desired trait and make them the parents of the next generation.
lamarckian evolution
principle that physical changes in organisms during their lifetime could be transmitted to their offspring.
fitness
the number of copies of ones genes that endure in later generations.
- improved by evolution.
primary neurulation
at 0-4 wees, the CNS of the embryo beings to develop, forming neural tube.
secondary neurulation
in 4th week, neural tube differentiates into 3 interconnected chambers (give rise to 3 major parts of the brain, forebrain, midbrain, hindbrain).
What happens at week 8?
structures of the CNS are formed, but amount of cells and tissue rapidly increases through neurogenesis.
stages of neurogenesis
- proliferation
- migration
- differentiation
- myelination
- synaptogenesis
Proliferation
production of new cells
ventricular zone
a layer of cells that line the inside of the neural tube.
progenitor cells
- in ventricular zone
- divide & give rise to CNS
progenitor cells undergo ___________ division and __________ division.
symmetrical; asymmetrical.
Symmetrical division
gives rise to two identical cells; increases the size of the V zone and the brain.
Asymmetrical division
gives rise to another progenitor cell & a neuroblast which then differentiates into glia cell/neuron, which migrates away from V zone towards the brain.
Migration
each new cell to be produces must pass through all the cells that came before it.
asymmetrical division gives rise to
- radial cells
- Cajal-Retzius cells
- migrating neurons
both ____________ and _____________ continue throughout life.
synaptogensis; myelination.
how do axons find their way?
- axons form synapses with target cells by following a chemical gradient.
- survival of fittest axon.
electricity activity during early development is __________
critical in forming synapses.
Apoptosis
- programmed cell death.
- begins at 3 months if axon doesn’t make contact w post synaptic cell.
Neurotrophins
- in PNS
- necessary for survival of neuron.
- ex; Nerve Growth Factor & Brain Derived Neurotrophic Factor.
how does experience change the brain?
- changes in dendritic branching over time.
- changes in neural connectivity & cortical structure.
Reorganization of brain thought
- regrowth of axons
- collateral sprouts
- receptor super-sensitivity
- learned adjustment in behaviour
- reorganization
Law of segregation
- each inherited trait is defined by a gene pair.
- offspring inherit one genetic ale form each parent when sex cells unite in fertilization.
law of independent assortment
genes for different traits are sorted separately from one another so that inheritance of one trait is not dependent on inheritance of another.
law of dominance
an organism with alternate forms of a gene will express the form that is dominant.
Four bases of RNA
adenine, guanine, cystosine, uracil
PTC sensitivity
dominant gene T
Autosomal genes
- all chromosomes except sex-linked genes.
Duplication/deletion
- form of mutation
- part of a chromosome that ordinarily appears once might instead appear twice or not at all.
FOXP2
human FOXP2 gene differs from the chimpanzee version = modified the human brain and vocal apparatus.
example of duplication
trisomy 21
example of deletion
William’s syndrome, deletion of chromosome 7
epigenetic inheritance
- dutch famine & risk for offspring
- parental trauma = PTSD, anxiety in offspring.
Identical twins share _________ of their genes.
100%
Fraternal twins share _________ of their genes.
50%
Concordant
if both twins carry a disease.
Discordant
if only one twin carries the disease.
