An acentric fragment is one result of crossing-over between a normal chromosome and a chromosome that has undergone what kind of rearrangements?

Question

(a) paracentric inversion

(b) duplication

(c) reciprocal translocation

(d) pericentric inversion

Answer 1

A duplication expands the chromosome by adding new copies of the gene(s) involved. A reciprocal translocation swaps one piece of a chromosome for the same piece on the homolggous chromosome. Neither of these events the centromere and would not result in an acentric fragment.

The difference between a pericentric inversion and an paracentric inversion is where the inversion takes place relative to the centromere. In a pericentric inversion, the inverted fragment extends to each side of the centromere. This region forms a loop with a non-inverted chromosome during meiosis.When crossing over occurs, each of the resolved chromosomes will have a single cetromere. In a paracentric inversion the inverted region does not involve the centromere. It will also form a loop with a non-inverted chromosome during meiosis. However, in this case one of the resolved cross-over chromosomes will have no centromere, or it is acentric. Another resolved chromosome will have two centromeres separated by DNA derived from each of the homologous chromosomes. This region is called a dicentric bridge and will break randomly when the two centromeres separate as meiosis continues.

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