Can you locate the inverted

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Can you locate the inverted segment?
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The cross-over products of inversions are
seldom viable---only non-recombinant (parental)
gametes typically survive meiosis. Therefore,
inversions seem to suppress crossing
over. What effect might this have on apparent
map distances in mapping crosses?
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Variegated position effect
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Effects of inversions

• 1. Suppression of crossing over.
• 2. Reduction of fertility.
• 3. Position effects (variegated)

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This is a classical Robertson- ian translocation
or centric fusion. It occurred in a herd of
Danish dairy cattle. What would you predict
about the fertility of the translocation
heterozygotes like this one?
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Heterozygotes for Robertsonian translocations
have problems at meiosis because of the
formation of multivalents. Consider a
heterozygote with original chromsomes A and
B (not homologus) and the fused metacentric
chromosome A---B. A trivalent forms at
prophase of meiosis
A B
A---B There
are three possible types of M1 segregation A,
A---B / B A / A---B, B A, B /
A---B Only the last segregation pattern leads to
balanced gametes or zygotes---the others result
in aneuploidy---zygotes with an extra copy of A
or B.
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Familial Down Syndrome A Robertsonian
translocation involving chromosomes 14 and
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Robertsonian translocations are frequently
implicated in the evolutionary divergence of
related species. For example Horse (Equus
caballus) 2N 64 Donkey
(Equus asinus) 2N 62 Grevys
zebra (Equus grevyi) 2N 34 How many
Robertsonian translocations might separate each
pair of species? What would be the diploid
chromosome number of a mule?

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The Philadelphia chromosome
A somatic translocation associated with a
particular form of cancer