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For example, Trisomy 16 is the most common trisomy in human pregnancies, occurring in more than 1% of pregnancies; only those pregnancies in which some normal cells occur in addition to the trisomic cells, or mosaic trisomy 16, survive. This condition, however, usually results in spontaneous miscarriage in the first trimester.
Polyploidy occurs in some tissues of animals that are otherwise diploid, such as human muscle tissues. This is known as endopolyploidy . Species whose cells do not have nuclei, that is, prokaryotes , may be polyploid, as seen in the large bacterium Epulopiscium fishelsoni . [45]
Specialty. Medical genetics. Aneuploidy is the presence of an abnormal number of chromosomes in a cell, for example a human cell having 45 or 47 chromosomes instead of the usual 46. [1] [2] It does not include a difference of one or more complete sets of chromosomes. A cell with any number of complete chromosome sets is called a euploid cell.
A chromosomal abnormality, chromosomal anomaly, chromosomal aberration, chromosomal mutation, or chromosomal disorder is a missing, extra, or irregular portion of chromosomal DNA. [1] [2] These can occur in the form of numerical abnormalities, where there is an atypical number of chromosomes, or as structural abnormalities, where one or more ...
Karyotype. A karyotype is the general appearance of the complete set of chromosomes in the cells of a species or in an individual organism, mainly including their sizes, numbers, and shapes. [1] [2] Karyotyping is the process by which a karyotype is discerned by determining the chromosome complement of an individual, including the number of ...
Patau syndrome. Patau syndrome is a syndrome caused by a chromosomal abnormality, in which some or all of the cells of the body contain extra genetic material from chromosome 13. The extra genetic material disrupts normal development, causing multiple and complex organ defects. This can occur either because each cell contains a full extra copy ...
Robertsonian translocation ( ROB) is a chromosomal abnormality where the entire long arms of two different chromosomes become fused to each other. It is the most common form of chromosomal translocation in humans, affecting 1 out of every 1,000 babies born. [1] It does not usually cause medical problems, though some people may produce gametes ...
Euploidy ( Greek eu, "true" or "even") is the state of a cell or organism having one or more than one set of the same set of chromosomes, possibly excluding the sex-determining chromosomes. For example, most human cells have 2 of each of the 23 homologous monoploid chromosomes, for a total of 46 chromosomes.