Title: Chapter 5 Recorded Lecture Speaker: Title: What Anthony is the title Berger/Angela of this lecture? Williams Speaker: Amit Dhingra Created by: (remove if same as speaker) online.wsu.edu
Chapter Five Genetics and Development of the Human Brain
Learning Objectives for Ch. 5 Discuss the role of genes as the building blocks of human nature, distinguishing between genotypes, gene expression, and phenotypes Describe the main source of genetic diversity Assess the importance of heritability and epigenetics to our understanding of the interactions between genetics and environment Explain the processes of neurogenesis, migration, differentiation, apoptosis, synaptogenesis, and myelination Analyze the importance of critical periods of development Summarize the features and causes of developmental disorders affecting neural growth Describe the changes in the nervous system that accompany normal aging
Genetics and Behavior The interaction between genetics ( nature ) and the environment ( nurture ) can influence physical and behavioral traits
From Genome to Trait Human genome Two sets of 23 chromosomes Identical in almost all cells Genotype Constructed by adenine (A), cytosine (C), guanine (G), and thymine (T). Composed of alleles (homozygous vs. heterozygous)
From Genome to Trait (cont d.) Phenotype Gene expression converts the genetic instructions into features of a living cell Imprinted genes Expression is determined by the parental origin of the gene
Three Alleles Give Rise to Four Types of Blood
The Process of Gene Expression
Sources of Genetic Variability Meiosis 2 23 unique egg/sperm cells can be produced per person Mutations Errors of DNA replication Sex Chromosomes Sex-linked characteristics
Cell Division by Meiosis
Crossing Over Contributes to Genetic Diversity
The X and Y Chromosomes
Probabilities of Hemophilia
SNPs and CNVs Single nucleotide polymorphisms (SNPs) DNA sequence change at one nucleotide Ex) AAGGTTAA and ATGGTTAA Copy-number variations (CNVs) Variable numbers of genes or gene series Associated with autism spectrum disorder and schizophrenia
Heritability The contribution of genetics to the variation of a trait observed in a population Heritability always refers to a population, not to individuals Heritability cannot be assessed without taking the environment into account Twin and adoption studies Minnesota Study of Twins Reared Apart
Epigenetics Reversible genetic change Not a DNA sequence change Influenced by environmental factors Determines gene expression patterns Histone modifications DNA methylation Presence of methyl groups associated with gene silencing Abnormal DNA methylation associated with disease
DNA Methylation and Histone Modification
DNA Methylation and Child Maltreatment
Building a Brain: Prenatal Development Zygote forms from fusion of egg and sperm Early differentiation Cell germ layers ectoderm, mesoderm, and endoderm Neural plate, neural groove, neural tube Formation of prosencephalon, mesencephalon, and rhombencephalon
Division of the Neural Tube
Nervous System Development: Neurogenesis and Migration Neurogenesis Formation of neurons and glia Originate from cells in the ventricular zone Progenitor cells divide by mitosis Cell migration Guided by radial glia Cells in cerebral cortex arrive in an inside-out fashion
Neurogenesis
Radial Glia Guide the Migration of New Cells
Nervous System Development: Differentiation Differentiation of neural tube along the dorsal and ventral halves and along the rostralcaudal axis Influenced by differentiation-inducing factors (DIFs) Organization of cerebral cortex affected by intrinsic and extrinsic factors
Nervous System Development: Axon and Dendrite Growth Axons and dendrites arise from neurites Developing axons and dendrites end in growth cones Filapodia and lamellipodia
Growth Cones Respond to a Variety of Cues
Nervous System Development: Formation of Synapses Synaptic specificity neurite identification of the correct target cell Movement of receptors to the synaptic site is guided by presynaptic and postsynaptic structures Interaction with target cells influences the type of neurotransmitter released by the presynaptic cell
Steps in the Formation of a Synapse at the Neuromuscular Junction
Nervous System Development: Cell Death Apoptosis = programmed cell death Access to Nerve growth Factors (neurotrophins) influence the survival of a neuron
Nervous System Development: Synaptic Pruning Reduces the number of functional synapses Influenced by neutrophins and functionality of the synapse
Nervous System Development: Myelination Occurs in rostral direction starting with the spinal cord, then hindbrain, midbrain, and forebrain Begins at 24 weeks postconception, with a burst around the time of birth Prefrontal cortex not completely myelinated until early adulthood
Effects of Experience on Development Plasticity The ability to rearrange synaptic connections Experience and the visual system Early in development, cells of LGN and primary visual cortex receive input from both eyes Experience with sensory information influences segregation of ocular dominance
Input from Both Eyes Competes for the Control of Target Cells in the LGN
Early Experience Affects the Organization of Ocular Dominance Columns
Effects of Experience on Development (cont d.) Experience and social behavior Imprinting in several species of birds Social deprivation in children Ending a critical period Conclusion of growth spurt in myelin coincides with reduced abilities to learn additional languages Epigenetics may play a role
Effects of Enriched Environments
Disorders of Nervous Development Neural tube defects Anencephaly Spinal bifida Genetic disorders Down syndrome Fragile-X syndrome Phenylketonuria (PKU) Environmental toxins Fetal alcohol syndrome
Fragile X Syndrome
Fetal Alcohol Syndrome Produces Physical and Intellectual Abnormalities
The Brain in Adolescence and Adulthood Puberty Surge of gray matter development and pruning Thickening of cortex; frontal lobe Amygdala matures first Explains teen risky behavior The Teen Brain: Still Under Construction http://www.nimh.nih.gov/health/publications/the-teen-brain-still-underconstruction/index.shtml?utm_source=lifesitenews.com+daily+newsletter&utm _campaign=2c0fa9560b-lifesitenews_com_intl_full_text_12_18_2012#pub2
White Matter Disruption and Binge Drinking
The Adult Brain Brain is fully mature at age 25; weight of brain starts to decrease at age 45 Neurogenesis Adult learning and memory Decline of neurogenesis associated with cognitive decline Important to distinguish between healthy aging and disease conditions