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1、分子分析课件,Ascomycetes () Ascomycetes are fungi that form their meiotic progeny in a asci (ascus,).,This allows the products of meiosis (called a tetrad，四分子) to be recovered together. Some ascomycetes have order asci.,Unordered Tetrad,Ordered Tetrad,粗糙链孢霉,酿酒酵母,分子分析课件,Our old friend, Neurospora,Neurospor
2、a is a haploid organism that makes asci with 8 spores.,Neurospora Life cycle,粗糙链孢霉,同时的,分子分析课件,教材p70,一种能产生分生孢子的特殊真菌菌丝,植物生长的,分子分析课件,Tetrad Analysis（四分子分析）,Analysis of all four products of a single meiosis.,N. crassa spores are formed by a single mitotic division after the completion of meiosis. The me
3、iotic progeny of N. crassa form in a asci (ascus), but they are present in a linear order that reflects meiotic division. Ordered tetrads in Neurospora allow mapping relative to the centromere.,分子分析课件,Producing an Ordered Tetrad,性细胞,分子分析课件,Neurospora Meiosis This shows the process of meiosis in N. c
4、rassa.,Remember that the duplicated chromosomes that are held together by the centromere segregate during the first meiotic division. Thus, a locus that is close to the centromere would often segregate during the first meiotic division.,分子分析课件,MI Segregation Pattern,No crossover between gene and cen
5、tromere,分子分析课件,MII Segregation Pattern,Crossover between gene and centromere,A second-division segregation Pattern, M2,Recombination between the gene of interest and the centromere would produce second division segregation tetrads.,分子分析课件,Producing MII Segregation Patterns,教材p180 的4种交换型,分子分析课件,Tetra
6、ds produced by second division segregation are related to the distance from the centromere by this equation:,R = (1/2 second-divison / total ) x 100% = cM,Ordered Tetrads in Neurospora Allow Mapping Relative to the Centromere, MII/total x 100% = cM,Or,分子分析课件,Genetic Analyses with Tetrads,Cross two h
7、aploid cells,Induce diploid to undergo meiosis,分子分析课件,Genetic Analyses with Tetrads,分子分析课件,Producing MII Segregation Patterns,The distance in cM between a and b can be estimated.,分子分析课件,Parental Ditype (PD),Tetratype (TT),Nonparental Ditype (NPD),这没有完全概括教材的P185，请补充完整,分子分析课件,Calculating Genetic Dista
8、nces with Tetrad Analysis,分子分析课件,Page 184 (教材上册),分子分析课件,Page 184 (教材上册),分子分析课件,Page 184 (教材上册),Distance from a to centromere = MII = (1+8+1) = 0.05 = 5 map units Total 100,Distance from b to centromere = MII = (18+8+1) = .135 = 13.5 map units Total 100,Distance from a to b = T + NPD = (18+1+1) +1 = .11 = 11 map units Total 100,分子分析课件,Page 184 (教材上册),
