PSB2000 Exam 1 Lecture Summary C Robison Instructor Lecture 2 Genes and Behavior It is evident that a great deal of an animal s behavior including that of humans is dependent upon genetic factors This is because genes code for proteins which determine the function of cells The function of neurons in the CNS is what determines behavior Therefore genes influence behavior but do not directly cause it Basic Genetics Behavior is adaptive Behaviors persist because they helped our ancestors survive o Those ancestors passed on their genes to us o Those shared genes shape and otherwise influence our brains Genes are stored as DNA in the nucleus of our cells o DNA is bundled into units called chromosomes o DNA codes for proteins complex workhorse biomolecules inside our cells o The DNA must be transcribed into copies of RNA molecules which go outside of the nucleus o These RNA templates are then translated into proteins You have two copies of each of your genes one from mom and one for dad o You get one copy of each chromosome from each parent If you have two copies of the same gene i e mom and dad both gave you the same gene you are homozygous If the gene copies are different you are heterozygous o Dominant traits are those that express in the heterozygous condition Ex if you have one gene copy for brown hair and one copy for blond hair you will have brown hair since the brown gene is dominant o Recessive traits are those that express only in the homozygous condition Ex if you have blue eyes you must have received a copy of the blue eyed gene from each parent because the blue gene is recessive When DNA is transcribed to RNA it is called gene expression When RNA is translated to protein it is called protein expression Behavioral Genetics You can tell if a behavioral trait is heritable passed on through genes by observing its expression in families Twin studies are especially popular o Example Examine identical versus fraternal twins Both identical and fraternal twins share the same environment But identical twins have 100 of the same gene but fraternal twins only have 50 Traits that are more correlated between identical twins probably have a genetic component Page 1 of 14 PSB2000 Exam 1 Lecture Summary C Robison Instructor There are some confounding effects systematic problems in twin studies o Shared prenatal environment may account for some of the similarities o The multiplier effect may amplify small initial behavior differences Some traits are sex linked This means the gene for that trait is located on one of the sex chromosomes usually the X chromosome o One example is a form of red green color blindness Its gene is located on the X chromosome Females have 2 X chromosomes so they are only color blind if they have two copies on the gene one on each X Males have only one X chromosome so they are color blind if they have one copy of the gene since they only get one copy via the X Some genes are sex limited These genes are present in both sexes but require something that is present in only one of the sexes o For example the genes for baldness can be present in both males and females o Baldness requires high circulating testosterone o Since females don t have high testosterone they don t develop baldness even if they have the gene Epigenetics Ultimately it is gene expression that determines the heritability of traits You can change gene expression by making DNA more or less accessible o This is called epigenetics One example is high licking and grooming HLG versus low licking and grooming LLG rats o HLG rats have pups that grow up to be HLG and LLG rats have LLG pups o If you take a pup from an LLG mother and give it to an HLG mother she will grow up to be HLG But if you block epigenetics you block this change and she will be LLG just like her real mom Epigenetics is different from genetics since there is no actual change to the DNA only how the DNA is accessed by the cell Page 2 of 14 PSB2000 Exam 1 Lecture Summary C Robison Instructor Lecture 3 Cells of the Nervous System Cells are the basic building blocks of all tissues of the body including the nervous system The cells of the nervous system can be broadly divided into two classes of cells neurons the main signaling units of the nervous system and glia the main support cells Introduction to Cells All cells have several distinct internal structures called organelles The organelles include o The nucleus a membrane enclosed area where the DNA is located The DNA is what codes for most of a cell s biochemical properties o The cell membrane which keeps the inside of the cell separate from the outside and controls the movement of molecules in and out o The mitochondria which act as the cell s main fuel producers o The endoplasmic reticulum which regulates the production and transport of proteins Each type of cells e g muscle neuron liver is distinct because the DNA in that cell expresses a certain subset of its genes o Different genes different tissue types o This causes different cell types to be shaped and behave differently The cell membrane controls the transport of ions o Only small chargeless molecules e g water and oxygen can pass the membrane o Ions are charged and need the help of special ion channels in the cell membrane to without help cross Sodium Na Potassium K Chloride Cl and Calcium Ca2 ion movement is important to the function of all cells especially neurons Neurons system NS areas Neurons are the cells responsible for conducting signals and processing info in the nervous o They receive signals from other cells process the info and relay their signals to other There are many different subtypes of neurons o They are categorized by their size shape neurotransmitters and membrane receptors o Neurons connect into networks to perform complex calculations In addition to the normal organelles neurons have several special features o Dendrites are long branchlike projections that get signals from other neurons Dendrite means tree they are shaped like branches They receive signals from the axon terminals of other neurons o Signals pass through the main body of the cell called the soma The soma acts as the cell s support system o The axon hillock is where the decision to activate the neuron is made Page 3 of 14 PSB2000 Exam 1 Lecture Summary C Robison Instructor o The axon is a long projection that the neuron s action potential signal travels down Some axons are insulated by a special substance called the myelin sheath This increases
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