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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

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Genetics

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  1. Genetics

  2. 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

  3. 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

  4. Gene Genotype Phenotype Chromosome Locus Allele Diploid Haploid Gamete Zygote Recessive Dominant Homozygous Heterozygous Key Terms

  5. 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

  6. 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

  7. How DNA works • Base pairs • Adenine • Thymine • Cytosine • Guanine • C -> G • A -> T

  8. DNA and genes • Genes encode proteins • DNA -> RNA • RNA -> Proteins • Proteins -> phenotype • Environment -> genes • Though some genes are less responsive than others

  9. 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

  10. Leslie and Rick • Aa and Aa • Or some variation • aA and Aa • Aa and aA • aA and aA • Phenotypically normal

  11. 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

  12. 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

  13. 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

  14. 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…….

  15. 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.

  16. 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

  17. Teenage Mutant Ninja Hamsters • Single Gene effect • Affects brain development • SCN specifically • May be cognitive effects

  18. Learning Mutants in Drosophila • The white rat of genetics • Dunce • Amnesia • Stuck • Coitus interruptus • Bang sensitive • Per • This one is cool…

  19. 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

  20. 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!!!!

  21. Remember, Genotype is NOT Phenotype

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