Chromosome mutations can be grouped into three basic categories: chromosome rearrangements, aneuploids, and polyploids. Chromosome rearrangements alter the structure of chromosomes; for example, a piece of a chromosome might be duplicated, deleted, or inverted. In aneuploidy, the number of chromosomes is altered: one or more individual chromosomes are added or deleted. In polyploidy, one or more
I 9.4 Chromosome banding is revealed by special staining techniques.
(Part a, Leonard Lessin/Peter Arnold; parts b and c, Dr. Dorothy Warburton, HICC, Columbia University; part d, Dr. Ram Verma/Phototake).
complete sets of chromosomes are added. Some organisms (such as yeast) possess a single chromosome set (1n) for most of their life cycles and are referred to as haploid, whereas others possess two chromosome sets and are referred to as diploid (2n). A polyploid is any organism that has more than two sets of chromosomes (3n, 4n, 5n, or more).
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