Behavioral Neuroscience Exam 2 02 25 2014 Genetics and Epigenetics DNA RNA Proteins Gene expression Transcription DNA partially unwinds RNA made Translation RNA instructs ribosomes to produce amino acids Complete Protein DNA sugar phosphate backbone adenine thymine guanine Proteome proteins encoded and expressed by genome Genes proteins cells behavior Genotype genetic instructions Phenotype observable traits Genomics Nucleus of each human somatic cell contains 23 pairs of chromosomes 46 total One from mother one from father 1 22 are autosomes 23 is sexual characteristics Mitochondrial DNA mDNA originates from mother Alleles alternative versions of particular gene Homozygous two identical alleles Heterozygous two different alleles Gene Expression genetic instructions converted into a feature of a living cell Dominant Genes those that mask other gene effects routinely expressed Recessive Genes genes that are expressed only in absence of a dominant gene routinely not expressed Complete Dominance Only the dominant allele s trait is expressed in the phenotype trait is only partial Incomplete Dominance The phenotypic expression of the dominant allele s Codominance The traits of both alleles of a gene pair are expressed completely in the phenotype Meiosis and Crossing Over planned variety Mutations replication errors Single nucleotide Polymorphisms SNPs Genetic mutations Can have positive neutral or negative effects May be specific or wide spread Sickle Cell Anemia Negative effects Poor oxygen capacity Positive effects Some protection against malaria Chromosomal abnormality down syndrome Sex Linked characteristics Hemophilia Color blindness in males and females Viewed as a second code X Chromosome inactivation One x is silenced to equalize protein production Epigenetics Environment can influence whether or not a gene is expressed Describes how single genetic code produces cell differentiation Explains how single genome can code for many phenotypes Describes how cells can go astray and produce diseases Epigenetic mechanisms influence protein production Blocks gene to stop transcription Unlocks gene to allow transcription Histone modification DNA may unwrap or be stopped from unwrapping from the histone blocked DNA modification Transcription of DNA into mRNA may be enabled or mRNA modification mRNA translation may be enabled or blocked Chimeric Animals genes behaviors combined from two parent species Knock In functioning gene s inserted into animals cells and is expressed Knock Out Inactivation of a gene so that it is not expressed Brain Development 3 perspectives on brain development brain development behavior behavior brain development hormones genes experience injury behavioral or brain development which can influence each other Neural development Zygote fertilization to 2 weeks Embryo 2 to 8 weeks Fetus 9 weeks birth Germ layers Ectoderm outer layer becomes skin and neural tissue Mesoderm middle layer becomes connective tissue such as ligaments muscles blood vessels and urogenital system Endoderm inner layer becomes many internal organs Early Neural Development Neural Plate 3 weeks after conception Thickened region of the ectodermal layer that gives rise to the neural tube Neural Tube Structure in the early stage of brain development from which the brain and spinal cord develop Stages of neural development 1 Cell Birth neurogenesis gliogenesis 2 Cell Migration 3 Cell Differentiation 4 Cell Maturation dendrite axon growth 5 Synaptogenesis formation of synapses 6 Cell Death Synaptic Pruning 7 Myelogenesis formation of myelin Cell Birth Subventricular Zone Lining of neural stem cells surrounding the ventricles in adults Progenitor Cell Precursor cell derived from a stem cell it migrates and produces a neuron or glial cell o Neuroblast and Glioblast Neurotrophic Factor A chemical compound that acts to support growth and differentiation in developing neurons May help keep certain neurons alive in adulthood Epidermal Growth Factor EGF Stem cell Progenitor cell Basic Fibroblast Growth Factor bFGF Progenitor cell Neuroblast Stem progenitor blast specialized Cell proliferation Cells that will become neurons divide and multiply at the rate of 250 000 new cells every minute Occurs in ventricular zone Cell Migration Neurons move from ventricular zone outward to final location Inside out migration Cell Differentiation Neuroblasts and glioblasts become specific types of cells Begins soon after migration Essentially complete at birth but maturation continues throughout adulthood Filopodia long fingerlike extensions from growth cones of neurites Lamellipodia flat sheet like extensions from core of growth cones Synaptogenesis Interaction with target cells influences the type of neurotransmitter released by the presynaptic cell Movement of receptors to the synaptic site guided by chemical release by presynaptic and postsynaptic structures Cell Death and synaptic pruning Brain produces extra neurons Excess neurons and synapses must be eliminated 1 Late or off target neurons die 2 Organization refined 3 Synapses strengthened or weakened depending on firing Cell Life and Death Neurotrophins chemical factors that influence the survival of a neuron Apoptosis programmed cell death Myelinogenesis Occurs in rostral direction starting with the spinal cord then hindbrain midbrain and forebrain Burst in myelination around the time of birth Prefrontal cortex not completely myelinated until early adulthood Light zones fast Disorders of Brain Development Neural Tube Defects Anencephaly Spinal bifida Genetic Disorders Down syndrome Fragile X syndrome PKU Environmental Toxins Fetal alcohol syndrome Neural Plasticity nervous systems ability to change 1 Before birth and until maturation is complete 2 During learning LTP 3 Following injury and degeneration 4 Stem cells specialized cells 5 Neurogenesis new neurons in adult brain Vision and Visual Perception Visible Spectrum The Advantages of Light as a Stimulus Electromagnetic energy is abundant and travels quickly in fairly straight lines The Electromagnetic Spectrum Range of energy visible to humans falls between 400 and 700 nanometers Absorption Reflection and Refraction Absorption and reflection determine colors we see Air and water refract or change the direction of traveling waves of light Brightness Intensity of reflected light that reaches our eyes Hue Color of light Structures of the Eye Color Mixing Additive light Subtractive paint Lens Transparent disk that