Tutorial 10 Q5-9 - 5. Two isolated strains of a diploid...

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1 5. Two isolated strains of a diploid organism were found to differ with respect to chromosome #6. Mapping experiments showed the following gene orders in two different strains. Strain A A * B C D E F G H I Strain B a * b c d h g f e i Strain A is homozygous for the standard sequence and strain B is homozygous for the inverted sequence. a) What chromosomal change would account for this difference? (two words) b) A cross between strain A and Strain B would result in a paracentric inversion heterozygote . If the centromere had been between F&G instead of A&B, then it would have been called a _______________ inversion heterozygote . c) Both paracentric and pericentric inversion heterozygotes can be phenotypically normal. Suggest a reason why this is so. d) It is difficult for the chromosomes to pair properly, but they try their best. The chromosomes pair with as much homology as possible so one chromosome has to form a loop. Fig 9-11, p244 shows how this is accomplished. Draw this pairing arrangement (the standard chromosome on top and the inversion chromosome on the bottom) as it would appear at diplotene of meiosis I and include a crossover between E & F of the inside non-sister chromatids. In fig 9-12b shows how the bivalent would look at diplotene of meiosis I. e)
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Tutorial 10 Q5-9 - 5. Two isolated strains of a diploid...

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