page_title: Polysomy
section_title: Chromosome 8
hierarchical_section_title: Polysomy / In mammals / In humans / Chromosome 8
caption_attribution_description: BONE MARROW: ACUTE MYELOBLASTIC LEUKEMIA WITH MATURATION (AML-M2) ASSOCIATED WITH A t(8;21) CHROMOSOME ABNORMALITY Bone marrow smear from a 23-year-old female with acute myeloblastic leukemia with maturation associated with a t(8;21) chromosome abnormality. The numerous myelocytes have abundant cytoplasm with prominent specific granulation. One of the myeloblasts to the left of center contains a prominent Auer rod. (Wright-Giemsa stain)
context_page_description: Polysomy is a condition found in many species, including fungi, plants, insects, and mammals, in which an organism has at least one more chromosome than normal, i.e., there may be three or more copies of the chromosome rather than the expected two copies. Most eukaryotic species are diploid, meaning they have two sets of chromosomes, whereas prokaryotes are haploid, containing a single chromosome in each cell. Aneuploids possess chromosome numbers that are not exact multiples of the haploid number and polysomy is a type of aneuploidy. A karyotype is the set of chromosomes in an organism and the suffix -somy is used to name aneuploid karyotypes. This is not to be confused with the suffix -ploidy, referring to the number of complete sets of chromosomes.
  Polysomy is usually caused by non-disjunction during meiosis, but may also be due to a translocation mutation. Polysomy is found in many diseases, including Down syndrome in humans where affected individuals possess three copies of chromosome 21.
  Polysomic inheritance occurs during meiosis when chiasmata form between more than two homologous partners, producing multivalent chromosomes.
context_section_description: Tetrasomy and hexasomy 8 are rare compared to trisomy 8, which is the most common karyotypic finding in acute myeloid leukemia (AML) and myelodysplastic syndromes (MDS). AML, MDS, or myeloproliferative disorder (MPD) with a high incidence of secondary diseases and a six-month survival rate are associated with a polysomy 8 syndrome.
caption: AML-M2 associated with chromosome 8 abnormality
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