Slide 1:Thinking about the Biology of Behavior Chapter 2 Evolution, Genetics, and Experience


Slide 2:Genetic Code and Genetic Expression Structural genes express themselves by synthesizing proteins for body cells Operator genes control structural genes by determining the time of expression and type of body cell produced DNA binding proteins turn operator cells on and off Environmental cues influence release of DNA binding proteins by the host cell


Slide 3:Genetic Code and Genetic Expression (continued) Mechanism of gene expression Strand of DNA unravels Messenger RNA (mRNA) synthesized from DNA mRNA leaves nucleus and attaches to ribosome in the cell’s cytoplasm Ribosome synthesizes protein according to 3-base sequences (codons) of mRNA


Slide 4:Genetic Code and Genetic Expression (continued) Mitochondrial DNA Mitochondria are the energy-generating structures found in the cytoplasm of all cells Mitochondria have their own DNA Mitochondria were once believed to come from mother, but paternal mitochondrial DNA has been found in one individual


Slide 5:Genetic Code and Genetic Expression (continued) Mitochondrial DNA (continued) Research interest in mitochondrial DNA Mitochondrial DNA may be responsible for some disorders Constant rate of mitochondrial DNA mutation has been used as evolutionary clock to determine, for instance, that hominids evolved in Africa and spread around the world Modern genetics Human genome project mapped the 3 billion base sequences of human DNA, as well as those of some other species


Slide 6:Genetic Code and Genetic Expression (continued) Humans were found to have only about 25 thousand genes, leading to new discoveries: At least some genes must produce more than one protein “Small RNA” has an expanded role in gene expression beyond carrying information from the nucleus Pseudogenes were once thought to be inactive evolutionary remnants. However, they are now thought to influence the structural genes


Behavioral Development: TheInteraction of Genetic Factorsand Experience :Behavioral Development: TheInteraction of Genetic Factorsand Experience Three influential studies Selective breeding of “maze-bright” and “maze-dull” rats Phenylketonuria: a single-gene metabolic disorder Development of birdsong


Selective Breeding of “Maze-Bright” and “Maze-Dull” Rats (continued) :Selective Breeding of “Maze-Bright” and “Maze-Dull” Rats (continued) Tryon (1934) interbreeds rats that make fewest maze mistakes; interbreeds rats that made most maze mistakes. Evidence for influence of genetic factors in the ontogeny of behaviors


Selective Breeding of “Maze-Bright” and “Maze-Dull” Rats :Selective Breeding of “Maze-Bright” and “Maze-Dull” Rats 0 % Maze-dull rats did not make significantly more errors than maze-bright rats when both were raised in enriched environments


Slide 10:Phenylketonura: A Single-Gene Metabolic Disorder Due to single mutant recessive gene Special diet during critical period of development lessens mental retardation An example of interaction of genetics and environment


Slide 11:Development of Birdsong Young males must hear their species’ songs during critical period, or they develop abnormal songs Young male canaries have left-side neurological dominance for song, like human left dominance for speech Adult male canaries grow new neurons each spring: an early discovery of adult neurogenesis


Slide 12:The Genetics of Human Psychological Differences Minnesota study of twins reared apart showed that identical twins are more similar to each other than fraternal twins on all psychological dimensions Example: Correlations of the IQ s of identical twins whether raised together or apart is larger than that of fraternal twins raised together


IndividualDifferences :IndividualDifferences Correlations of IQ for identical and fraternal twins, reared together or apart


Slide 14:Individual Differences (continued) Heritability estimates refer to populations, not to individuals cannot be generalized to populations from dissimilar environments Multiplier effect – genetically similar individuals seek out similar environments Turkheimer (2003) – heritability of IQ was near 0 in impoverished twins and near 1 (maximum) in affluent twins


Daily Quiz 2 :Daily Quiz 2 Describe how structural genes are expressed, that is, transcribed and then translated into proteins. Use a diagram in your answer.


Daily Quiz 2 :Daily Quiz 2 25% for describing the transcription of mRNA 50% for describing the translation of mRNA to protein 25% for a diagram of the process