In the diagram at the right, the chromosome pair with dominant genes (capital letters) has undergone an inversion that did not contain the centromere. Its gene arrangement
is: ABJIHGFEDCKL. During meiotic prophase, a crossover event occurs adjacent to the F gene which can cause serious complications for the future of the cell. For example, start at the designated (1) chromatid and trace the path of the chromosome through the crossover to its end. What unusual phenomenon do you encounter? Repeat the process with designated chromosome (2). Again, what happens. Scroll down the window for the answer.
The chromosme fragment designated as (1) will be joined to two cntromeres and carry the gene sequence: ABJIHGFedcba... meaning there will be duplicatios of some genes. The chromosome fragment designated as (2) will not have any centromere and carry the gene sequence: LKCDEfghijkl. Again some duplications. However since there is no centromere, this fragment will likely be lost in subsequent divisions and the daughter cells will be seriously deficient in requisite genes. Note that both affected chromosomes carry duplications as well as deletions. Neither one then has a complete set of genes. The chromosome with two centromeres will likely be torn apart at anaphase when different portions of its structure are moved to opposite ends of the cell. To trace designated chromosome 1, click on the TRACE button. For a diagram of how such a division figure might look, flip to the next card.
