Transcript Genetics
Genetics Genetics and Behaviour For behaviour to be affected by natural selection, some variation in behaviour must be inherited If not, the characteristics could not be passed on right? Otherwise, could contribute to fitness, but could NOT evolve Remember, only heritable, genetically transmitted variation can be affected by selection Introduction ‘Trying to determine how much of a behaviour is due to genetics and how much is due to the environment is like trying to determine how much the area of a field is caused by its length and how much by its width’ Donald Hebb Nature v. Nurture is a stupid argument Key Terms Gene Genotype Phenotype Chromosome Locus Allele Diploid Haploid Gamete Zygote Recessive Dominant Homozygous Heterozygous Note that it is not the case that the chromosomes just pair off, there is also recombination So, each sex cell is a little bit different This Recombination is the source of much genetic variation, and it occurs in all but the simplest organisms Mutation is the ONLY source of new genetic material Most mutations are bad, usually lethal Some are neutral Some (very few) confer an advantage How DNA works Base pairs Adenine Thymine Cytosine Guanine C -> G A -> T QuickTime™ and a TIFF (U ncompressed) decompressor are needed to see this picture. DNA and genes Genes encode proteins DNA -> RNA RNA -> Proteins Proteins -> phenotype Environment -> genes Though some genes are less responsive than others QuickTime™ and a TIFF (U ncompressed) decompressor are needed to see this picture. An Example Human Ocular cutaneous albinism I wonder where that example came from….. Single gene for the production of melanin A – normal a - bad Dominance / Recessive relationship AA, aA, Aa all lead to normal, aa leads to me Leslie and Rick Aa and Aa Or some variation aA and Aa Aa and aA aA and aA Phenotypically normal 1 in 4 chance of having a kid with aa They did, on June 23, 1965 My genotype MUST be aa because there is no dominance They got the looks, but I got the brains…….. Danny and Stephanie may be carriers, or they may not be, they are phenotypically normal Their kids could carry the allele, assuming they do My kids MUST carry the allele, as they had an a from me, and, an A from Isabelle We know they got an A from Isabelle by looking at their phenotype Behavioural Effects I don’t spend much time in the sun I have very poor vision (20/200, melanin guides the growth of the visual system) No binocular vision Can’t drive a car Not very good at baseball Huge IQ……. Partial Dominance Telleogryllus oceanicus and T. commodus Males call to attract mates (function) Song is species specific Male hybrids produce hybrid song Female hybrids prefer hybrid song. Another cool example Mutant hamsters Martin Ralph Tau gene TT normal 24 hr cycle tt 20 hr cycle Tt or tT gives 22 hr cycle Teenage Mutant Ninja Hamsters Single Gene effect Affects brain development SCN specifically May be cognitive effects Learning Mutants in Drosophila The white rat of genetics Dunce Amnesia Stuck Coitus interruptus Bang sensitive Per This one is cool… So why are there different alleles? On the surface, if some allele is better than some other, why does it not replace all other alleles? Neutral alleles? Environmental fluctuation Heterozygote superiority Frequency dependent selection And, of course, mutation So, What Does it All Mean? What does ‘a gene for behaviour’ mean? Behavioural difference caused by genetic difference Does not mean that a complex behavioural sequence is caused by a single gene Many other genes contribute to behaviour Some difference must be caused by genetic differences Just because something has a genetic basis does not make in unchangeable!!!! Remember, Genotype is NOT Phenotype