Lecture VII - Lecture VI I 1. L ife cycle of an ascomycete...

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Lecture VII 1. Life cycle of an ascomycete fungus with ordered tetrads a. Possible to tell products of meiosis 1 and meiosis 2 b. Map gene to centromere distance 2. How to do that…? a. Both red chromatids go to one pole and blue goes to its own pole b. First division segregation i. Orginial cell (o |c) ii. oo|cc iii. cc|oo iv. o = A v. c= a vi. this is what happens with no crossover between a gene and its centromere 1. you gets first division segregation – fancy way of saying separation c. now imagine if there is a crossover i. orginal cell (o |c) – oc |oc ii. oocc (Aa |Aa) iii. Second division segregation 1. Happens due to a crossover between the genes and its centromere iv. Used to map distance between the gene and the centromere 3. Example of ordered tetrad analysis a. Only one map distance a to b b. But because its ordered tetrads – a to centromere and b to centromere c. First we do a to b distance i. If PD = NPD is unlinked ii. If PD > NPD it is linked iii. Parental ditype = 161 + 21 iv. Non parental ditype = v. Tetratype = 103 + 15
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vi. a-b distance = (1/2 TT + 3NPD )/ total *100 = (118/2)/300 = 19.7 cM [map distance between a and b] d. now we will do a to centromere i. divide tetrads in half ii. see if its first division segregation 1. if we have 2 a’s in the first half we give it a 1 if we have 1 a we give it a 2 iii. so for a 1 st div segregation = 161+15 iv. so for 2 nd div segregation = 103+21 v. map distance form a to centromere = 62/300 x100 = 20.7 1. 62 = .5*124 = second div segergation e. now we do b to centromere i. 1 . 2 .2 . 1 (ignore a this time) ii. 15+21 = 36
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This note was uploaded on 09/29/2011 for the course GENETICS 380 taught by Professor Glodowski during the Spring '08 term at Rutgers.

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Lecture VII - Lecture VI I 1. L ife cycle of an ascomycete...

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