Guest
FRUIT FLY GENETICS Patterns of Inheritance and Studying Crosses Genes control what an organism looks like and there are many different variants of each gene. Fruit fly eyes can be red, white, scarlet, sepia, prune, maroon,or vermilion. Each of these many variants of a gene is called an allele. When you see fruit flies in a lab, though, you will notice that most of them have red eyes. They also have tan bodies, large flat wings, and other specific traits. This is because current fly research is largely based on the research done by T. H. Morgan in the 1920's. Morgan happened to work in New York, and studied the kind of flies you might find living on overripe fruit in that area of the world. Because Morgan did so much work on these flies, they have become a sort of historical reference point that we use to this day. Any trait that corresponds to this reference point we call wild type. Any characteristic that differs from wild type is a variant or a mutant. Red eyes are wild type, and all those other colors are variants. Saying a trait is wild type doesn't mean it is a better trait, and calling something a mutation doesn't mean it is bad. Mutations lead to more diversity of traits. The terminology simply makes it easier for geneticists to understand each other - we are all using the same traits as a reference point. This also allows us to use shorthand to refer to the different traits. A wild type trait is usually shown with a sign. The mutant phenotypes are indicated by a letter or abbreviation. For example: white eye color is represented as w. Alleles and how they work Drosophila carry two copies of every chromosome, which means two copies of each gene. If the organism has two copies of the same allele, it is said to be homozygous. If it has one copy each of two different alleles, it is heterozygous. We write the genotype showing both alleles: a wild type is / . White eyed would be w/w. If a mutant allele is dominant, a fly needs only one copy of the allele to show the phenotype. This mutant is represented by a capital letter. Curly wings, Cy, is a dominant allele. If the mutation is recessive, a fly needs to have two copies of the allele, one on each chromosome, to develop the phenotype. Eyeless, ey, is a recessive allele that results in very small eyes. Knowing whether a trait is recessive or dominant can be very important. If a pregnant woman has a rare disease, she will want to know whether she will pass it on to her child or not. You can't know just from looking whether a certain trait is recessive or dominant. In humans it is sometimes very difficult to determine; it is necessary to look at elaborate family trees for several generations of one family to find the patterns of inheritance. In fruit flies it is much easier because we can set up controlled crosses in which we mate flies of known genotypes. The numbers of their offspring with certain phenotype informs us of how the trait is inherited. #geneticInformation #meiosis #viruses #ChromosomeArm #Promoter #punnettSquare #AminoAcids #CellCulture #centromere #DaughterCells #FrancisCrick #SisterChromatid #fruitFlyGenetics #mutation #PCR #lawOfProbability #Morphogenesis #Inbreeding #population #cytosine #chromatin #DrosophilaMelanogasterOrganismClassification #Haploid #Nucleotide #Primers #bloodType #breedingExperiment #NaturalSelection #autosomal #TurnerSyndrome #TumorCells #hardyWeinbergPrinciple #genotypes
