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The Consequence of Inversion

Can differences between members of a homologous pair interfere with the normal process of meiosis? Crossing over requires that members of a homologous pair line and attach so that alleles from the same locus are spatially associated in a very exact fashion. Otherwise the genetic material that gets switched in crossing over may not be equivalent with potentially catastrophic events. Genetic accidents such as inversions can either interfere with meiosis or they can require the chromosomes to contort during meiosis to allow proper attachment. An inversion reverses a sequence of DNA on a chromosome. Unless the inversion breaks up a gene this does not affect the function of the chromosome during interphase. However it will either complicate or prevent crossing over during prophase I.

View the animation below, then complete the quiz to test your knowledge of the concept.






1Consider a normal chromosome with the following gene sequence along its length: F G H I J K L. Which of the following sequences represents an inversion?
A)F G H K L
B)H I J K L
C)F G H I J K J K L
D)J K L F G H I
E)none of the above



2An inversion is best be described as a
A)change in the DNA from an A-T base pair to a G-C basepair.
B)change from the homozygous to the heterozygous state.
C)change from the dominant to the recessive form of a gene.
D)reversal in the orientation of a segment of a chromosome.
E)reversal of the sex of an individual.



3In meiosis, a chromosome carrying an inversion
A)cannot pair with a normal homologous chromosome.
B)can only pair with a chromosome carrying the same inversion.
C)can only pair with a chromosome carrying a different inversion.
D)can pair with a normal homologous chromosome by forming an internal loop.
E)can pair with any non-homologous chromosome.



4Inversions never alter gene expression.
A)True
B)False



5An inversion results in an increase in the amount of DNA on a chromosome.
A)True
B)False







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