Presentation on theme: "*Lab manual protocol will not be used"— Presentation transcript:
1*Lab manual protocol will not be used Drosophila Genetics IInheritance, Autosomal genes vs. Sex Linked genes, Monohybrid and Dihybrid Crosses*Lab manual protocol will not be used
2Lab ObjectivesTo have a first hand look at how genes are inherited in the model organism Drosophila melanogaster (Fruit Fly)To develop a better understanding of genetics by conducting monohybrid and dihybrid crosses.To have a basic knowledge of working with Drosophila as a model organism
3Overview Review Mitosis and Meiosis Review Concepts of Genetics Drosophila melanogasterBackground InformationApplied Genetics
6Allele-alternate forms of a given gene (brown or blue eyes) Independent assortment- random distribution of unlinked genes into gametes.Linked Genes- genes located on the same chromosome tend to be inherited together. The alleles do not assort independently.Sex linked genes- genes located on a sex chromosome (e.g. white eyes in Drosophila)Crossing over- reciprocal exchange of genetic material between non-sister chromatids during meiosis I (performed in pipe cleaner exercise during meiosis).
18Genotype Phenotype vg / vg +_ Nomenclature Autosomal Genes (use + for wt allele)Convention dictates that we denote genotypein the following fashion:GenotypePhenotype+ / +wt (homozygous)vg / +wt (heterozygous)vg / vg+_mutantwt (homo. or het.)
19Autosomal Gene Nomenclature Wild-type genes located on autosomal chromosomes are donated “+” by convention(note that a separate system is used for sex-linked genes--module 10)(Each allele is represented and is seperated by a “/”)GenotypePhenotype+ / +wt (homozygous)vg / +wt (heterozygous)vg / vgmutant
20TerminologyWild type- the normal or most common phenotype in a population.Mutant Phenotype- traits that are alternates to the wild type. Changes due to mutations in the wild type.wtebonyWhite body
21Monohybrid CrossCross breeding organisms while tracking one trait.
22Example Monohybrid Cross x vgvg(Wildtype) (Vestigial)
26Assignment I Worksheet Refer toAssignment I Worksheet
27Dihybrid CrossCross breeding organisms while tracking two traits
28Example Dihybrid Cross x bb vgvg(Wild type) (Black vestigial)This is not the cross that you will design on your worksheets.See worksheet for Assignment I for fly lab and complete the dihybrid cross.
29Test CrossA testcross is a valuable way to use a genetic cross to determine the genotype of an organism that shows a dominant phenotype but unknown gentoype.
30Example Test Cross +_ x vgvg (Unknown) (Vestigial) If the F1 progeny are all WT the genotype of the unknown fly is +/+.If the F1 progeny are a mix of wild-type and vestigial flies, the genotype of the unknown fly is +vg.
31Goals Observe Male/Female flies Observe various phenotypes of flies Comprehend:Test CrossMonohybrid CrossDihybrid CrossChi Square TestView these all in virtual flylab.