BIOL 3333 1st Edition Lecture 12Outline of Last Lecture Interaction of 4 phenotypesComplementary gene actionRecessive suppressionRecessive epistasisDominant epistasisContinuous VariationMultifactorial inheritance r+ geneA.H SturtevantCurrent LectureT.H Morgans Laboratory Found: - that linkage experiments in Drosophila support the chromosomal theory of inheritance - genes are linked thru all generations - no random mixing - genes are arrayed in a linear order along the length of a chromosome - homologs carry the same array of gene loci, but not necessarily the same alleles Least common class of recombination:- double recombinant chromatids- 2 crossovers flanking the middle geneHow to determine gene order:- compare non recombinant and double recombinant classesHow to know if genes are linked?- will not be produced in a 1:1:1:1 etc ratioMost common class of recombination:parental allelic combinations- they represent non-recombinant chromatids Mapping thru recombination:- allows us to determine gene positions relative to each otherMapping thru recombination DOES NOT allow us to determine gene positions relative to one anotherInterference evidence of: crossing over in one area can decrease likelihood of exchange in an adjacent areaAssortment for genes on different chromosomes: independent with 1:1 ratioThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.What is RF for genes located far apart on same chromosome:RF is 50%Max. map distance b/w 2 genes is 50 map units- can never exceed 50 MU in any given cross*Multiple crossovers lead to an underestimate of true genetic distanceTo find most accurate map distance: sum distances calculated for short intervals *In ascomycetes: fungi are haploid for majority of life cycle Transient diploid cell formed: when strains of 2 different mating types combine- cell will then undergo meiosis, trapping all meiotic products within a single structure *the ability to recover all products of a single meiotic division:- permits mapping of a gene relative to centromere of the chromosome- it will give info at the molecular level on the process of recombinationIf no crossover occurs b/w a gene and the centromere a 4:4 pattern should be expected *If no crossover occurs a 2:2:2:2 pattern should be expected*A 4:4 pattern indicates that no recombination has occurred*A 2:2:2:2 or 2:4:2 pattrn indicates