PSB2000 Final Review Exam 1 Genetics genes and enviro interact to shape human behavior genes are aligned along chromosomes and come in pairs genes are a portion of a chromosome and is composed of DNA the order of DNA bases determines gene function DNA is transcribed to RNA dna is copied into rna RNA is translated to protein rna creates proteins proteins are the workhorses of the cell proteins determine the development of the body by forming part of the structure of the body serving as enzymes biological catalysts that regulate chemical reactions in the body homozygous a person has an identical pair of genes on the two chromosomes heterozygous a person has an unmatched pair of genes on the two chromosomes genes are either dominant recessive or intermediate a dominant gene shows a strong effect in either the homozygous or heterozygous condition a recessive gene shows its effect only in the homozygous condition Autosomal genes all other genes except for sex linked genes Sex linked genes genes located on the sex chromosomes Sex linked Genes since the X is bigger sex linked genes usually refer to X linked genes sex limited genes are genes that are present in both sexes but mainly have an effect on one sex males and females develop differently according to differences in exposures to different factors the expression of a gene is sometimes contingent upon exposure to those factors if the factor isn t present then the gene s trait will not be expressed Epigenetics a field that is concerned with changes in gene expression without the modification of the DNA sequence some genes are active only at a certain point in one s life a certain time of day etc differences are a likely explanation for differences between monozygotic identical twins What you do at any moment not only affects you now but produces epigenetic effects that alter gene expressions for a longer period of time experiences alter the activity of genes Example of Epigenetics rat moms lick and groom their young Some are good mothers and some are bad if you take the pup of a low grooming mother and give it to a high grooming mother she ll grow up to be high grooming If you block epigenetic regulation then the pup will still grow up to be low grooming licking and grooming behavior is epigenetically regulated Heredity and Environment almost all behaviors have both a genetic component and an enviro component Researchers study monozygotic one egg and fraternal two eggs twins to infer contributions of heredity and environment they also study adopted children and their resemblance to their biological parents to infer hereditary influences Heritable Traits transgenic mutant animals see how gene changes affect traits and subsequent behavior Studying a trait with no gene target family studies see what traits run in families twin sibling studies tell us how much of the trait is heritable Twin Study traits like personality and intelligence run in families but families often share values so upbringing is also similar identical twins have identical genes identical genetics prenatal enviro fraternal twins share 50 of their DNA differing genes same prenatal enviro so heritable traits should be more similar in identical twins than in fraternal twins Separating Genetics and Upbringing the prenatal enviro plays a role if twins are brought up in different enviros but share the same traits genes don t directly produce behaviors genes produce proteins that increase the probability that a behavior will develop under certain circumstances Multiplier Effect small initial differences in behavior may be self reinforcing this is a type of positive feedback mechanism this can make us overestimate heritability Parts of a Cell Neurons contain the following structures Membrane controls what gets in the cell what the cell eats and when the neuron fires many membrane problems are also protein problems nucleus a structure that contains the chromosomes mitochondria structure that performs metabolic activities and provides energy that the cells require ribosomes sites at which the cell synthesizes new protein molecules endoplasmic reticulum network of thin tubes that transport newly synthesized proteins to their location Neurons vary in size shape and function the shape of a neuron determines its connection with other neurons and contribution to the nervous system interneurons aka intrinsic neurons those whose dendrites and axons are completely contained within a single structure motor neuron its soma is in the spinal cord sensory neuron is specialized at one end to be highly sensitive to a particular type of simulation andhas the soma in the middle widely branching dendrites of some cerebral cells enable up to 20 000 inputs vs retnal cells have few inputs the function is closely related to the shape of a neuron they have the following major components Soma cell body contains the nucleus mitochondria ribosomes and other structures found in other cells responsible for the metabolic work of the neuron Presynaptic Terminals axon terminals are the end points of an axon where the release of chemicals to communicate with other neurons Axon thin fiber of a neuron responsible for transmitting nerve impulses toward other neurons organs or muscles some neurons are covered with an insulating material called the myelin sheath Dendrites they are branching fibers with a surface lined with synaptic receptors responsible for bringing info into the neuron some dendrites also contain dendritic spines that further branch out and increase the surface area of the dendrite the greater the surface area of the dendrite the more info it can receive Vocabulary Afferent axon refers to bringing info into a structure Efferent axon refers to carrying info away from the structure Neuron to Neuron Signals 1 Dendrites receive a signal 2 If there are enough signals current goes through the soma 3 The current can trigger a signal at the base of the axon 4 The signal travels down the axon to the axon terminal 5 This releases neurotransmitters into the synaptic cleft 6 These are received by the dendrites of another neuron 7 Rinse wash repeat Glia the other major component of the nervous system Astrocytes help synchronize the activity of the axon by wrapping around the presynaptic terminal and taking up chemical by the axon branches of the astrocyte in the center surround the presynaptic terminals of related axons if a few of them are active at once the astrocyte absorbs some of the chemicals they
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