BI226 Chapter 7: CHAPTER 7.docx
Document Summary
Introduction: genetic recombination results from physical exchanges between homologous chromosomes in meiosis. A chiasma is the site of crossing-over where this reciprocal exchange takes place: map distance between genes is measure in map units (mu). 1 mu is the interval in which 1 percent of crossing-over takes place: as the distance between genes increases, the incidence of multiple crossovers causes the recombination frequency to be an underestimate of the true map distance. Early studies of genetic linkage: morgan"s experiments with drosophila. By 1911 morgan had identified several x-linked genes including white eye (w) and miniature wing (m). Crossed a white miniature female (wm/wm) with a wild-type male (w+m+/y) May also be written: (w m/ w m)( w+ m+ /x y chromosome. Parentals: in the f2 the most common class of phenotypes was the parental type (or grandparental type in this case). White eyed, miniature winged and wild type eyes, wild type wings for a total of 1,541 flies.