The chromosomal crossover article says ( first paragraph ) that if chromosomes break and rejoin on opposite sides of the centromere, the result can be one chromosome being lost during cell division.
12.
Synapsis begins before the synaptonemal complex develops and is not completed until near the end of prophase I . Crossover usually occurs when matching regions on matching chromosomes break and then reconnect to the other chromosome.
13.
But the team suggested that it might still cause chromosome breaks, by acting as a target for other enzymes that can cut DNA . Those enzymes, Reiter said, could be produced by other, active mariner transposons in the human genome.
14.
Some birth defects are known to be associated with missing a chromosome, having an extra chromosome, such as in Down syndrome, as well as by having a part of one chromosome break off and relocate to a portion of another chromosome ( called a translocation ).
15.
These diseases are associated with high incidence of chromosomal abnormalities, including chromosome breaks, complex rearrangements, deletions and translocations, site specific mutations, and in particular sister chromatid exchanges ( more common in BS ) that are believed to be caused by a high level of somatic recombination.
