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Complete trisomy (having three copies of the entire chromosome) is lethal within days after conception. [13] Some partial deletions and partial duplications produce birth defects. The following diseases are some of those related to genes on chromosome 1 (which contains the most known genetic diseases of any human chromosome):
Since 1991, out of the 47 possible disomies, 29 have been identified among individuals ascertained for medical reasons. This includes chromosomes 2, 5–11, 13–16, 21 and 22. [citation needed] [needs update]
Angelman syndrome; Other names: Angelman's syndrome [1] [2]: A five-year-old girl with Angelman syndrome. Features shown include telecanthus, bilateral epicanthic folds, small head, wide mouth, and an apparently happy demeanor; hands with tapered fingers, abnormal creases and broad thumbs.
Full tetrasomy of an individual occurs due to non-disjunction when the cells are dividing (meiosis I or II) to form egg and sperm cells (gametogenesis).This can result in extra chromosomes in a sperm or egg cell.
These microduplications likely represent the predicted reciprocal rearrangements to the microdeletions characterized in the 22q11.2 region. [2] Smaller microduplications may occur within this highly dynamic with frequent rearrangements using alternative low-copy repeats as recombination substrates within and distal to the DiGeorge syndrome region.
Distal 18q-A 9-year-old girl with phenotypic features of De Grouchy syndrome TYPE I (Monosomy 18p or deletion 18p or 18p-). This image does not show the phenotypic features of distal 18q (de Grouchy Type 2), which are quite distinct from those of Monosomy 18p
If a trisomic conception undergoes trisomic rescue in certain cells, including those that are destined to become the baby, then the remaining trisomy cells may be confined to the placenta. Several factors influence the pattern of normal and abnormal cells in the developing embryo .
In rare cases this translocation results in Down syndrome and Patau syndrome. [2] Robertsonian translocations result in a reduction in the number of chromosomes. A Robertsonian evolutionary fusion, which may have occurred in the common ancestor of humans and other great apes, is the reason humans have 46 chromosomes while all other primates ...