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Unformatted text preview: ssovers % expected double crossovers Interference reveals that the probability of one crossover event can reduce or increase the probability of the second crossover event. It is believed that interference is due to a regulatory process that limits the number of exchanges that can occur in a cell or along a pair of homologous chromosomes. March 19, 2012 BIS101001, Spring 2012--Genes and Gene Expression, R.L. Rodriguez 2012 41 Different Types of Interference Absolute Partial None Negative If dc=0 dc < expected dc expected=dc observed dc > expected 1 <1 0 - number Interference = 1- Coefficient of Coincidence, where Coefficient of Coincidence = % observed double crossovers % expected double crossovers March 19, 2012 BIS101001, Spring 2012--Genes and Gene Expression, R.L. Rodriguez 2012 42 Mapping Function Recombination Frequency (RF) increases as the distance between two loci increases, up to a point. 1% RF is equivalent to 1 map unit (m.u.) or 1 centiMorgan (cM) Double and higher multiple crossovers cause underestimates of map distances based on RF. Therefore, the best estim...
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