Answer
Three mechanisms leading to extra copies forming: unequal crossing over (leaves an extra copy of some of a chromosome on one copy and less on another), errors in DNA copying (DNA polymerase erroneously moves back and makes an extra copy of a gene during chromosome duplication), errors in cell division leaving extra copies of chromosomes in one daughter cell (duplicates whole chromosomes, including each gene on them).
Work Step by Step
Review Concept 21.5 and make a list of the mechanisms which show extra copies. Pay attention to the color-coded figures and look for extra segments of the same color.
