Genetics and Flying Things: LAB

Genes are our unit of inheritance, well, physically so to speak. Offspring receive genes from the parent(s) which insures the parents' mark be carried on in posterity. But how does it all work? What are in genes? Which genes do offspring exhibit?
The genes of a particular trait in an organism are the genotype. Genotypes are the combination of traits appearing from the parents. One characteristic of each parent will appear in the genotype. The individual characteristics are called alleles. For example, the genotype for horns on our beloved dragon were to have double horns.A double horn trait is represented by H while a single horn trait is represented by h. But, just because the phenotype (or observable trait of the genotype) is double horns does not mean that the genotype of the dragon is HH. In actuality the genotype was Hh with double horns being the dominant trait (that which will appear when present) and single horn being the recessive trait (that which will only appear when two recessive traits are present). We call the genotype of our dragon heterozygous. A homozygous genotype will have the phenotype of whichever alleles are represented. If our dragon's phenotype had been a single horn that the genotype would have been hh. We call this homozygous recessive.
Our fruit flies are a perfect example of this. Both of the parent flies had the phenotype for long wings. However, both of them had a long-wing genotype that was heterozygous. The punnet square shows the possible outcomes of any offspring. Of course, there was only the possibility of two phenotypes: long wings and short wings. However, there were three possible genotypes. Since both parents parents were heterozygous there was 1/4 possibility the offspring would be either homozygous dominant(long-winged) or homozygous recessive(short-winged). The other half possibility, 1/2 chance was that the posterity would be heterozygous, and therefore long-winged.
Chromosomes are certainly vital to evolution and mutations are passed at the genetic level. It is interesting that we would study a punnett activity on fruit flies, since they have been the subject of practical evolutionary studies for 100 years now. Since fruit flies have a generational period of 11-12 days it would be easy to see how mutations could transform a species in a limited amount of time. For example, humans have been around for a little over one million years, according to general scientific thought. The experiments on fruit flies have well exceeded that one million years, translated. The results? The thousands of mutations imposed, if put into one single fly, would not resemble anything of a new species. Most of these mutated flies die out or, more often, revert back to the wild type, as if there was some type of genetic fail safe!!! Then again, I am sure they just evolved the fail safe, so they would never have to change species again.
This was, certainly, a very fun lab. Why I didn't do this in junior high and high school, I am not sure. Now I know who to blame for my small hands. DAD!!!





Sources:

"Elusive Icons of Evolution What do Darwin's finches and the four-winged fruit fly really tell us?"
Jonathan Wellshttp://www.actionbioscience.org/evolution/nhmag.html