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Genetics of Down syndrome. Down syndrome is a chromosomal abnormality characterized by the presence of an extra copy of genetic material on chromosome 21, either in whole (trisomy 21) or part (such as due to translocations). The effects of the extra copy varies greatly from individual to individual, depending on the extent of the extra copy ...
Trisomy 21. Down syndrome (also known by the karyotype 47,XX,+21 for females and 47,XY,+21 for males) [98] is mostly caused by a failure of the 21st chromosome to separate during egg or sperm development, known as nondisjunction. [91] As a result, a sperm or egg cell is produced with an extra copy of chromosome 21; this cell thus has 24 ...
Medical genetics. Aneuploidy is the presence of an abnormal number of chromosomes in a cell, for example a human somatic 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.
Caused by abnormal cell division that results in extra genetic material on chromosome 21, this extra full or partial chromosome results in the developmental and physical differences seen in those ...
Leukemia (also spelled leukaemia; pronounced / luːˈkiːmiːə / [1] loo-KEE-mee-ə) is a group of blood cancers that usually begin in the bone marrow and produce high numbers of abnormal blood cells. [9] These blood cells are not fully developed and are called blasts or leukemia cells. [2]
Anaphase lag is a consequence of an event during cell division where sister chromatids do not properly separate from each other because of improper spindle formation. [1] The chromosome or chromatid does not properly migrate during anaphase and the daughter cells will lose some genetic information. It is one of many causes of aneuploidy.
Oncology. The Philadelphia chromosome or Philadelphia translocation (Ph) is a specific genetic abnormality in chromosome 22 of leukemia cancer cells (particularly chronic myeloid leukemia (CML) cells). This chromosome is defective and unusually short because of reciprocal translocation, t (9;22) (q34;q11), of genetic material between chromosome ...
In about 1 to 2% of persons of Down syndrome, mosaicism is seen — that is when some of the cells have 46 chromosomes (two No. 21 chromosomes) and some cells have 47 chromosomes (three No. 21 ...