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Unformatted text preview: pick one allele from your fish’s mate. This is allele 2 of the first offspring’s blue locus. You now have selected two alleles that represent the blue locus genotype of the first offspring. Write down the blue locus genotype in table 3, under “1st offspring”. Repeat steps 2‐4 for the green locus. The mating type of this offspring will be determined later Congratulations, your first offspring (#1) is developing. It won’t take long before it is born. Repeat the procedure above for the second offspring. Don’t forget to use the parental genotype to carry on the allele exchange, not that of offspring #1 (see table 3 for parental genotype). Write down offspring #2 genotype in table 3. Allow your parental fish to die. Bring back parental alleles in one of the allele containers near the spawning grounds. Now allow the offspring to be born: flip a coin to determine who between you and the other students (your fish’s mate) will become offspring #1 and offspring #2. Your new fish may have a different genotype. Use the extra allele cards located in the containers if needed. In order to keep the male/female ratio constant throughout the lab, you will keep the same mating type during the whole experiment. Write down the genotype of your new fish in the second “Parent 1 Genotype line” of table 3. A new generation of fish now lives in the lake. When the whole class has reached the next generation, return to one of the spawning ground and find a new mate. You cannot select a fish with which you have exchanged genes in the previous generation to prevent inbreeding. Repeat the allele exchange procedure two more times. When you’re done, write down your final offspring genotype on the blackboard to perform class calculation. Answer Questions 11‐16 77 Lab4 ‐ Microevolution 4‐ Mutation and Selection In this exercise, we will study the transmission of new allele types in the population. These alleles appeared in the population by mutation of one of the previous alleles. In addition to increasing genetic diversity in the population, these new alleles will introduce a new factor: selection. So far, all alleles at the blue or green loci had the same relative fitness, which means that they did not influence the reproductive success of the fish that carry them. Now, the new allele of the blue locus (called B1) confers an advantage to the fish that carry it. We mentioned before that locus B controls the shape of fins, and mutant fish with the B1 allele (B1 mutants) have more efficient fins that allow them to escape from predators. Thus, these individuals have an increased chance of surviving until reproduction time compared to the non‐mutants (wild type). Answer Question 17. A new allele also appeared at the green locus (which controls the mouth size). Fish that carry this allele (G1 mutants) possess a larger mouth that allows them to catch larger pieces of food. However, the lake is very rich in nutrients of various sizes so that all the fish can feed thems...
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- Fall '08