IB31Lecture+outline+8+Mendelian+Genetic+III+Feb+15+Sp08 -...

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IB 31, Spring, 2008 2/15/2008 IV. Single-gene effects on complex behaviors often involve controlling thresholds for expression A. Dilger's study of nest-building behavior in Love Birds. All species tear strips of nesting material and carry them back to nesting area for use in construction. However: 1. Agapornis personata , Fischer's Love Bird, carries nesting material in bill. 2. Agapornis roseicollis , Peach-faced Love Bird, tucks material in flank feathers. 3. F 1 picks up material in bill, tucks, but doesn't let go. Months after first attempts at nesting, birds were successful carrying material only 41% of the time. Even two years later, they were still having some difficulty. Although they had learned to carry, they still turn their head toward the flank before flying. Both behaviors are present and are in conflict. Thresholds for two behaviors probably set by different homozygous recessive genes, in heterozygous hybrids, behaviors expressed. B. Teal and Pin-tail drake courtship studied by Lorenz. By imprinting male ducklings on foster mothers of the other species, he was able to breed teal to pin-tails. While both species lack the down-up courtship display common in other ducks, the hybrids displayed it. AAbb x aaBB model. Can’t test this because hybrids are sterile. C. These examples suggest that while complex behaviors are governed by many genes, their expression may be controlled by just a few loci that affect thresholds. V. Recently, there have been some interesting studies showing the basis for single gene effects on behavior in Hymenoptera (bees, ants, wasps) A. Fire ants are a major pest invading U.S. They bite with jaws to hold on
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and inject from the tip of the abdomen a venom that causes extreme pain. (work by Krieger and Ross) Fire ant invasive behavior is in part determined by whether a colony has a single queen (monogynous) or multiple queens (polygynous). 1 Single queens establish colonies on their own after a mating flight. The queen feeds her young. The colony does not permit additional queens and any new queen that shows up is killed. 2. Multiple queen colonies spread by budding – one or more queens and many workers quickly forming a new colony. This forms one giant interconnected super colony. Colonies can have 2-200 queens and will accept queens from neighboring nests. 3. Selection on invasive fronts favors the faster spreading and competitively superior polygyne colonies. 4. This difference in behavior is due to a single gene, Gp-9. It encodes a pheromone binding protein that governs recognition of other ants. The polygyne colonies have a mutant allele that causes workers not to distinguish among queens and they accept many of them. B. Honey bees. We already discussed how the behavior of workers changes with adult age. At first they stay in the hive and perform duties related to care of the young, construction, etc. Gradually, they move to the entrances and perform undertaking, air-conditioning, etc. After about two weeks, they start to leave the hive and become scouts and foragers.
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