GENE20001 Lecture Notes - Lecture 7: Zygosity, Centimorgan, Heterochromatin
Paracentric inversion: inversion that does not include the centromere. No addition or deletion
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Pericentric inversion: inversion that includes centromere
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Meiotic pairing in a paracentric inversion heterozygote: inverted region pairs as a loop. This is
a hallmark of heterozygote inversion
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Crossover within the inversion loop
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Inversions
7 Chromosomal Mutations (inversions, duplication)
Sunday, March 16, 2014
10:16 AM
Genetics Page 1
Document Summary
Paracentric inversion: inversion that does not include the centromere. Meiotic pairing in a paracentric inversion heterozygote: inverted region pairs as a loop. Genetics page 1 (blue arrows) dicentric: 2 centromeres (red arrows) acentric: no centromere. Meiotic pairing in a pericentric inversion heterozygote also forms an inversion loop. Deletion product tends to be non-(cid:448)ia(cid:271)le that"s (cid:449)hy (cid:449)e do(cid:374)"t o(cid:271)ser(cid:448)e re(cid:272)o(cid:373)(cid:271)i(cid:374)a(cid:374)ts. Note that the deletion products are missing one or more of gene abcde e. g. an inversion heterozygote of b to c. Pericentric inversions lead to duplication and deletion products. Homozygous for inverted chromosome does not require an inversion loop. Note there is a different gene order and thus different genetic distances apply. They reduce the observable recombination frequency between markers. This is because crossing over inside looped region leads to problematic gametes. However recombination outside the looped region is normal. Xyz and xyz recombinants measure the distance from x to the proximal (closer to centromere)breakpoint of the inversion.
