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Cat-eye syndrome (CES) or Schmid–Fraccaro syndrome is a rare condition caused by an abnormal extra chromosome, i.e. a small supernumerary marker chromosome. [2] This chromosome consists of the entire short arm and a small section of the long arm of chromosome 22.
Wolf–Hirschhorn syndrome (WHS) is a chromosomal deletion syndrome resulting from a partial deletion on the short arm of chromosome 4 [del(4)(p16.3)]. [3] Features include a distinct craniofacial phenotype and intellectual disability.
This results in an extra chromosome, making the haploid number 24 rather than 23. Fertilization of eggs or insemination by sperm that contain an extra chromosome results in trisomy, or three copies of a chromosome rather than two. [14] Trisomy 18 (47,XX,+18) is caused by a meiotic nondisjunction event.
Smith–Magenis syndrome (SMS), also known as 17p- syndrome, is a microdeletion syndrome characterized by an abnormality in the short (p) arm of chromosome 17. [1] It has features including intellectual disability, facial abnormalities, difficulty sleeping, and numerous behavioral problems such as self-harm.
Trisomy X occurs via a process called nondisjunction, in which normal cell division is interrupted and produces gametes with too many or too few chromosomes. Nondisjunction is a random occurrence, and most girls and women with trisomy X have no family histories of chromosome aneuploidy.
Human genetic disorders can be caused by ring chromosome formation. Although ring chromosomes are very rare, they have been found in all human chromosomes. Symptoms seen in patients carrying ring chromosomes are more likely to be caused by the deletion of genes in the telomeric regions of affected chromosomes, rather than by the formation of a ring structure itself. [5]
The terms "partial monosomy" and "partial trisomy" are used to describe an imbalance of genetic material caused by loss or gain of part of a chromosome. In particular, these terms would be used in the situation of an unbalanced translocation , where an individual carries a derivative chromosome formed through the breakage and fusion of two ...
Individuals with PKS present prenatally or at birth with multiple birth defects.These defects include: brain atrophy, agenesis of the corpus callosum, polymicrogyria of the brain, and/or spot calcifications in the brain's lateral sulcus; deafness and/or blindness; autonomic nervous system dysfunctions such as anhidrosis, hypohidrosis, and/or episodic spells of hyperventilation interspersed ...