Aneuploidy
Encyclopedia
Aneuploidy is an abnormal number of chromosome
s, and is a type of chromosome abnormality. An extra or missing chromosome is a common cause of genetic disorder
s (birth defects). Some cancer cells also have abnormal numbers of chromosomes. Aneuploidy occurs during cell division
when the chromosomes do not separate properly between the two cells. Chromosome abnormalities occur in 1 of 160 live births. The most common extra chromosomes among live births are 21, 18 and 13.
Different species have different numbers of normal chromosomes and thus the term "aneuploidy" refers to the chromosome number being different for that species.
in the human body, apart from enucleated red blood cell
s and the haploid gametes, has 23 pairs of chromosomes (for a total of 46). One copy of each pair is inherited from the mother and the other copy is inherited from the father. The first 22 pairs of chromosomes (referred to as autosomes) are numbered from 1 to 22, and are arranged from largest to smallest in a karyotype
(see figure). The 23rd pair of chromosomes are the sex chromosomes. Normal females have two X chromosomes, while normal males have one X chromosome
and one Y chromosome
.
During meiosis
, when germ cells divide to create sperm and egg (gametes), each half should have the same number of chromosomes. But sometimes, the whole pair of chromosomes will end up in one gamete, and the other gamete will not get that chromosome at all.
Most embryos cannot survive with a missing or extra autosome
(numbered chromosome) and are spontaneously aborted. The most frequent aneuploidy in humans is trisomy 16
, although fetuses affected with the full version of this chromosome abnormality do not survive to term (it is possible for surviving individuals to have the mosaic form, where trisomy 16 exists in some cells but not all). The most common aneuploidy that infants can survive with is trisomy 21, which is found in Down syndrome, affecting 1 in 800 births. Trisomy 18 (Edwards syndrome)
affects 1 in 6,000 births, and trisomy 13 (Patau syndrome) affects 1 in 10,000 births. 10% of infants with trisomy 18 or 13 reach 1 year of age.
Changes in chromosome number may not necessarily be present in all cells in an individual. When aneuploidy is detected in a fraction of cells in an individual, it is called chromosomal mosaicism. In general, individuals who are mosaic for a chromosomal aneuploidy tend to have a less severe form of the syndrome compared to those with full trisomy. For many of the autosomal trisomies, only mosaic cases survive to term. However, mitotic aneuploidy may be more common than previously recognized in somatic tissues, and aneuploidy is a characteristic of many types of tumorigenesis (see below).
usually occurs as the result of a weakened mitotic checkpoint, as these checkpoints tend to arrest or delay cell division until all components of the cell are ready to enter the next phase. If a checkpoint is weakened, the cell may fail to 'notice' that a chromosome pair is not lined up on the mitotic plate, for example. In such a case, most chromosomes would separate normally (with one chromatid ending up in each cell), while others could fail to separate at all. This would generate a daughter cell lacking a copy and a daughter cell with an extra copy.
Completely inactive mitotic checkpoints may cause non-disjunction at multiple chromosomes, possibly all. Such a scenario could result in each daughter cell possessing a disjoint set of genetic material.
Merotelic attachment occurs when one kinetochore
is attached to both mitotic spindle
poles. One daughter cell would have a normal complement of chromosomes; the second would lack one. A third daughter cell may end up with the 'missing' chromosome.
Multipolar spindles
: more than two spindle poles form. Such a mitotic division would result in one daughter cell for each spindle pole; each cell may possess an unpredictable complement of chromosomes.
Monopolar spindle: only a single spindle pole forms. This produces a single daughter cell with its copy number doubled.
A tetraploid intermediate may be produced as the end-result of the monopolar spindle mechanism. In such a case, the cell has double the copy number of a normal cell, and produces double the number of spindle poles as well. This results in four daughter cells with an unpredictable complement of chromosomes, but in the normal copy number.
cells, including trisomy 12 in chronic lymphocytic leukemia
(CLL) and trisomy 8 in acute myeloid leukemia
(AML). However, these forms of mosaic aneuploidy occur through mechanisms distinct from those typically associated with genetic syndromes involving complete or mosaic aneuploidy.
Loss of p53 creates genomic instability that most often results in the aneuploidy phenotype.
In addition, genetic syndromes in which an individual is predisposed to breakage of chromosomes (chromosome instability syndrome
s) are frequently associated with increased risk for various types of cancer, thus highlighting the role of somatic aneuploidy in carcinogenesis
. Studies indicate that aneuploidy directly contributes to carcinogenesis by disrupting the asymmetric division of adult stem cells.
, where an individual carries a derivative chromosome formed through the breakage and fusion of two different chromosomes. In this situation, the individual would have three copies of part of one chromosome (two normal copies and the portion that exists on the derivative chromosome) and only one copy of part of the other chromosome involved in the derivative chromosome.
Germline aneuploidy is typically detected through karyotyping, a process in which a sample of cells is fixed and stained to create the typical light and dark chromosomal banding pattern and a picture of the chromosomes is analyzed. Other techniques include Fluorescence In Situ Hybridization (FISH), Quantitative Polymerase Chain Reaction (PCR) of Short Tandem Repeat
s, Quantitative Fluorescence PCR (QF-PCR), Quantitative Real-time PCR (RT-PCR) dosage analysis, Quantitative Mass Spectrometry of Single Nucleotide Polymorphisms, and Comparative Genomic Hybridization
(CGH).
These tests can also be performed prenatally to detect aneuploidy in a pregnancy, through either amniocentesis
or chorionic villus sampling
. Pregnant women of 35 years or older are offered prenatal diagnosis
because the chance of chromosomal aneuploidy increases as the mother's age increases. For more information, see prenatal diagnosis
.
Recent advances have allowed for less invasive
testing methods based on the presence of fetal genetic material in maternal blood.
Chromosome
A chromosome is an organized structure of DNA and protein found in cells. It is a single piece of coiled DNA containing many genes, regulatory elements and other nucleotide sequences. Chromosomes also contain DNA-bound proteins, which serve to package the DNA and control its functions.Chromosomes...
s, and is a type of chromosome abnormality. An extra or missing chromosome is a common cause of genetic disorder
Genetic disorder
A genetic disorder is an illness caused by abnormalities in genes or chromosomes, especially a condition that is present from before birth. Most genetic disorders are quite rare and affect one person in every several thousands or millions....
s (birth defects). Some cancer cells also have abnormal numbers of chromosomes. Aneuploidy occurs during cell division
Cell division
Cell division is the process by which a parent cell divides into two or more daughter cells . Cell division is usually a small segment of a larger cell cycle. This type of cell division in eukaryotes is known as mitosis, and leaves the daughter cell capable of dividing again. The corresponding sort...
when the chromosomes do not separate properly between the two cells. Chromosome abnormalities occur in 1 of 160 live births. The most common extra chromosomes among live births are 21, 18 and 13.
Different species have different numbers of normal chromosomes and thus the term "aneuploidy" refers to the chromosome number being different for that species.
Chromosomes
Every cellCell (biology)
The cell is the basic structural and functional unit of all known living organisms. It is the smallest unit of life that is classified as a living thing, and is often called the building block of life. The Alberts text discusses how the "cellular building blocks" move to shape developing embryos....
in the human body, apart from enucleated red blood cell
Red blood cell
Red blood cells are the most common type of blood cell and the vertebrate organism's principal means of delivering oxygen to the body tissues via the blood flow through the circulatory system...
s and the haploid gametes, has 23 pairs of chromosomes (for a total of 46). One copy of each pair is inherited from the mother and the other copy is inherited from the father. The first 22 pairs of chromosomes (referred to as autosomes) are numbered from 1 to 22, and are arranged from largest to smallest in a karyotype
Karyotype
A karyotype is the number and appearance of chromosomes in the nucleus of an eukaryotic cell. The term is also used for the complete set of chromosomes in a species, or an individual organism.p28...
(see figure). The 23rd pair of chromosomes are the sex chromosomes. Normal females have two X chromosomes, while normal males have one X chromosome
X chromosome
The X chromosome is one of the two sex-determining chromosomes in many animal species, including mammals and is common in both males and females. It is a part of the XY sex-determination system and X0 sex-determination system...
and one Y chromosome
Y chromosome
The Y chromosome is one of the two sex-determining chromosomes in most mammals, including humans. In mammals, it contains the gene SRY, which triggers testis development if present. The human Y chromosome is composed of about 60 million base pairs...
.
During meiosis
Meiosis
Meiosis is a special type of cell division necessary for sexual reproduction. The cells produced by meiosis are gametes or spores. The animals' gametes are called sperm and egg cells....
, when germ cells divide to create sperm and egg (gametes), each half should have the same number of chromosomes. But sometimes, the whole pair of chromosomes will end up in one gamete, and the other gamete will not get that chromosome at all.
Most embryos cannot survive with a missing or extra autosome
Autosome
An autosome is a chromosome that is not a sex chromosome, or allosome; that is to say, there is an equal number of copies of the chromosome in males and females. For example, in humans, there are 22 pairs of autosomes. In addition to autosomes, there are sex chromosomes, to be specific: X and Y...
(numbered chromosome) and are spontaneously aborted. The most frequent aneuploidy in humans is trisomy 16
Trisomy 16
Trisomy 16 is a chromosomal abnormality in which there are three copies of chromosome 16 rather than two. It is the most common chromosomal cause of miscarriage during the first trimester of pregnancy....
, although fetuses affected with the full version of this chromosome abnormality do not survive to term (it is possible for surviving individuals to have the mosaic form, where trisomy 16 exists in some cells but not all). The most common aneuploidy that infants can survive with is trisomy 21, which is found in Down syndrome, affecting 1 in 800 births. Trisomy 18 (Edwards syndrome)
Edwards syndrome
Trisomy 18 is a genetic disorder caused by the presence of all or part of an extra 18th chromosome. It is named after John H. Edwards, who first described the syndrome in 1960...
affects 1 in 6,000 births, and trisomy 13 (Patau syndrome) affects 1 in 10,000 births. 10% of infants with trisomy 18 or 13 reach 1 year of age.
Changes in chromosome number may not necessarily be present in all cells in an individual. When aneuploidy is detected in a fraction of cells in an individual, it is called chromosomal mosaicism. In general, individuals who are mosaic for a chromosomal aneuploidy tend to have a less severe form of the syndrome compared to those with full trisomy. For many of the autosomal trisomies, only mosaic cases survive to term. However, mitotic aneuploidy may be more common than previously recognized in somatic tissues, and aneuploidy is a characteristic of many types of tumorigenesis (see below).
Terminology
In the strict sense, a chromosome complement having a number of chromosomes other than 46 (in humans) is considered heteroploid while an exact multiple of the haploid chromosome complement is considered euploid.| Number of chromosomes | Name | Description >- | 1 |
Monosomy | Monosomy Monosomy Monosomy is a form of aneuploidy with the presence of only one chromosome from a pair. Partial monosomy occurs when only a portion of the chromosome has one copy, while the rest has two copies.-Human monosomy:... refers to lack of one chromosome of the normal complement. Partial monosomy can occur in unbalanced translocations or deletions, in which only a portion of the chromosome is present in a single copy (see deletion (genetics)). Monosomy of the sex chromosomes (45,X) causes Turner syndrome Turner syndrome Turner syndrome or Ullrich-Turner syndrome encompasses several conditions in human females, of which monosomy X is most common. It is a chromosomal abnormality in which all or part of one of the sex chromosomes is absent... . >- | 2 |
Disomy | Disomy is the presence of two copies of a chromosome. For organisms such as humans that have two copies of each chromosome (those that are diploid), it is the normal condition. For organisms that normally have three or more copies of each chromosome (those that are triploid Ploidy Ploidy is the number of sets of chromosomes in a biological cell.Human sex cells have one complete set of chromosomes from the male or female parent. Sex cells, also called gametes, combine to produce somatic cells. Somatic cells, therefore, have twice as many chromosomes. The haploid number is... or above), disomy is an aneuploid chromosome complement. In uniparental disomy Uniparental disomy Uniparental disomy occurs when a person receives two copies of a chromosome, or part of a chromosome, from one parent and no copies from the other parent.. UPD could involve isodisomy or heterodisomy .... , both copies of a chromosome come from the same parent (with no contribution from the other parent). >- | 3 |
Trisomy | Trisomy Trisomy A trisomy is a type of polysomy in which there are three copies, instead of the normal two, of a particular chromosome. A trisomy is a type of aneuploidy .-Description and causes:... refers to the presence of three copies, instead of the normal two, of a particular chromosome Chromosome A chromosome is an organized structure of DNA and protein found in cells. It is a single piece of coiled DNA containing many genes, regulatory elements and other nucleotide sequences. Chromosomes also contain DNA-bound proteins, which serve to package the DNA and control its functions.Chromosomes... . The presence of an extra chromosome 21, which is found in Down syndrome Down syndrome Down syndrome, or Down's syndrome, trisomy 21, is a chromosomal condition caused by the presence of all or part of an extra 21st chromosome. It is named after John Langdon Down, the British physician who described the syndrome in 1866. The condition was clinically described earlier in the 19th... , is called trisomy 21. Trisomy 18 and Trisomy 13, known as Edwards and Patau Syndrome, respectively, are the two other autosomal trisomies recognized in live-born humans. Trisomy of the sex chromosomes is possible, such as in (47,XXX) Triple X syndrome Triple X syndrome is a form of chromosomal variation characterized by the presence of an extra X chromosome in each cell of a human female. The condition always produces females, with an XX pair of chromosomes, as well as an additional chromosome, resulting in the formation of XXX. A mosaic form... , (47,XXY) Klinefelter's syndrome Klinefelter syndrome, 46/47, XXY, or XXY syndrome is a condition in which human males have an extra X chromosome. While females have an XX chromosomal makeup, and males an XY, affected individuals have at least two X chromosomes and at least one Y chromosome... , and (47,XYY) XYY syndrome XYY syndrome is an aneuploidy of the sex chromosomes in which a human male receives an extra Y-chromosome, giving a total of 47 chromosomes instead of the more usual 46. This produces a 47,XYY karyotype... . >- | 4/5 |
tetrasomy/pentasomy | Tetrasomy Tetrasomy A tetrasomy is a form of aneuploidy with the presence of four copies, instead of the normal two, of a particular chromosome.-Full:Full tetrasomy of an individual occurs due to non-disjunction when the cells are dividing to form egg and sperm cells . This can result in extra chromosomes in a sperm... and pentasomy are the presence of four or five copies of a chromosome, respectively. Although rarely seen with autosomes, sex chromosome tetrasomy and pentasomy have been reported in humans, including XXXX XXXX syndrome XXXX syndrome is a rare chromosomal disorder caused by the presence of four X chromosomes instead of two X chromosomes. This condition occurs only in females, as there are no Y chromosomes present. Tetrasomy X was first described in 1961, and since then approximately 100 cases have been reported... , XXXXX, XXXXY 49 XXXXY syndrome 49, XXXXY Syndrome is an extremely rare, aneuploidic sex chromosomal abnormality; its frequency is approximately 1 out of 85,000 to 100,000 males.-Pathophysiology:... and XYYYY. |
Mechanisms
NondisjunctionNondisjunction
Nondisjunction is the failure of chromosome pairs to separate properly during meiosis stage 1 or stage 2. This could arise from a failure of homologous chromosomes to separate in meiosis I, or the failure of sister chromatids to separate during meiosis II or mitosis. The result of this error is a...
usually occurs as the result of a weakened mitotic checkpoint, as these checkpoints tend to arrest or delay cell division until all components of the cell are ready to enter the next phase. If a checkpoint is weakened, the cell may fail to 'notice' that a chromosome pair is not lined up on the mitotic plate, for example. In such a case, most chromosomes would separate normally (with one chromatid ending up in each cell), while others could fail to separate at all. This would generate a daughter cell lacking a copy and a daughter cell with an extra copy.
Completely inactive mitotic checkpoints may cause non-disjunction at multiple chromosomes, possibly all. Such a scenario could result in each daughter cell possessing a disjoint set of genetic material.
Merotelic attachment occurs when one kinetochore
Kinetochore
The kinetochore is the protein structure on chromatids where the spindle fibers attach during cell division to pull sister chromatids apart....
is attached to both mitotic spindle
Mitotic spindle
In cell biology, the spindle fibers are the structure that separates the chromosomes into the daughter cells during cell division. It is part of the cytoskeleton in eukaryotic cells...
poles. One daughter cell would have a normal complement of chromosomes; the second would lack one. A third daughter cell may end up with the 'missing' chromosome.
Multipolar spindles
Multipolar spindles
Multipolar spindles are spindle formations characteristic of cancer cells. Spindle formation is mostly conducted by the aster of the centrosome which it forms around itself...
: more than two spindle poles form. Such a mitotic division would result in one daughter cell for each spindle pole; each cell may possess an unpredictable complement of chromosomes.
Monopolar spindle: only a single spindle pole forms. This produces a single daughter cell with its copy number doubled.
A tetraploid intermediate may be produced as the end-result of the monopolar spindle mechanism. In such a case, the cell has double the copy number of a normal cell, and produces double the number of spindle poles as well. This results in four daughter cells with an unpredictable complement of chromosomes, but in the normal copy number.
Somatic mosaicism in the nervous system
Mosaicism for aneuploid chromosome content may be part of the constitutional make-up of the mammalian brain. In the normal human brain, brain samples from six individuals ranging from 2–86 years of age had mosaicism for chromosome 21 aneuploidy (average of 4% of neurons analyzed). This low-level aneuploidy appears to arise from chromosomal segregation defects during cell division in neuronal precursor cells, and neurons containing such aneuploid chromosome content reportedly integrate into normal circuits. These results suggest the possibility that somatic mosaicism in the brain (and perhaps, by extension, other tissues) may contribute to the diversity between individuals.Somatic mosaicism in cancer
Somatic mosaicism also occurs in many cancerCancer
Cancer , known medically as a malignant neoplasm, is a large group of different diseases, all involving unregulated cell growth. In cancer, cells divide and grow uncontrollably, forming malignant tumors, and invade nearby parts of the body. The cancer may also spread to more distant parts of the...
cells, including trisomy 12 in chronic lymphocytic leukemia
Chronic lymphocytic leukemia
B-cell chronic lymphocytic leukemia , also known as chronic lymphoid leukemia , is the most common type of leukemia. Leukemias are cancers of the white blood cells . CLL affects B cell lymphocytes. B cells originate in the bone marrow, develop in the lymph nodes, and normally fight infection by...
(CLL) and trisomy 8 in acute myeloid leukemia
Acute myeloid leukemia
Acute myeloid leukemia , also known as acute myelogenous leukemia, is a cancer of the myeloid line of blood cells, characterized by the rapid growth of abnormal white blood cells that accumulate in the bone marrow and interfere with the production of normal blood cells. AML is the most common acute...
(AML). However, these forms of mosaic aneuploidy occur through mechanisms distinct from those typically associated with genetic syndromes involving complete or mosaic aneuploidy.
Loss of p53 creates genomic instability that most often results in the aneuploidy phenotype.
In addition, genetic syndromes in which an individual is predisposed to breakage of chromosomes (chromosome instability syndrome
Chromosome instability syndrome
Chromosome instability syndromes are a group of inherited conditions associated with chromosomal instability and breakage. They often lead to an increased tendency to develop certain types of malignancies....
s) are frequently associated with increased risk for various types of cancer, thus highlighting the role of somatic aneuploidy in carcinogenesis
Carcinogenesis
Carcinogenesis or oncogenesis is literally the creation of cancer. It is a process by which normal cells are transformed into cancer cells...
. Studies indicate that aneuploidy directly contributes to carcinogenesis by disrupting the asymmetric division of adult stem cells.
Partial aneuploidy
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 translocationChromosomal translocation
In genetics, a chromosome translocation is a chromosome abnormality caused by rearrangement of parts between nonhomologous chromosomes. A gene fusion may be created when the translocation joins two otherwise separated genes, the occurrence of which is common in cancer. It is detected on...
, where an individual carries a derivative chromosome formed through the breakage and fusion of two different chromosomes. In this situation, the individual would have three copies of part of one chromosome (two normal copies and the portion that exists on the derivative chromosome) and only one copy of part of the other chromosome involved in the derivative chromosome.
Diagnosis
Short tandem repeat
A short tandem repeat in DNA occurs when a pattern of two or more nucleotides are repeated and the repeated sequences are directly adjacent to each other. The pattern can range in length from 2 to 5 base pairs and is typically in the non-coding intron region...
s, Quantitative Fluorescence PCR (QF-PCR), Quantitative Real-time PCR (RT-PCR) dosage analysis, Quantitative Mass Spectrometry of Single Nucleotide Polymorphisms, and Comparative Genomic Hybridization
Comparative genomic hybridization
Comparative genomic hybridization or Chromosomal Microarray Analysis is a molecular-cytogenetic method for the analysis of copy number changes in the DNA content of a given subject's DNA and often in tumor cells....
(CGH).
These tests can also be performed prenatally to detect aneuploidy in a pregnancy, through either amniocentesis
Amniocentesis
Amniocentesis is a medical procedure used in prenatal diagnosis of chromosomal abnormalities and fetal infections, in which a small amount of amniotic fluid, which contains fetal tissues, is sampled from the amnion or amniotic sac surrounding a developing fetus, and the fetal DNA is examined for...
or chorionic villus sampling
Chorionic villus sampling
Chorionic villus sampling , sometimes misspelled "chorionic villous sampling", is a form of prenatal diagnosis to determine chromosomal or genetic disorders in the fetus. It entails sampling of the chorionic villus and testing it...
. Pregnant women of 35 years or older are offered prenatal diagnosis
Prenatal diagnosis
Prenatal diagnosis or prenatal screening is testing for diseases or conditions in a fetus or embryo before it is born. The aim is to detect birth defects such as neural tube defects, Down syndrome, chromosome abnormalities, genetic diseases and other conditions, such as spina bifida, cleft palate,...
because the chance of chromosomal aneuploidy increases as the mother's age increases. For more information, see prenatal diagnosis
Prenatal diagnosis
Prenatal diagnosis or prenatal screening is testing for diseases or conditions in a fetus or embryo before it is born. The aim is to detect birth defects such as neural tube defects, Down syndrome, chromosome abnormalities, genetic diseases and other conditions, such as spina bifida, cleft palate,...
.
Recent advances have allowed for less invasive
Diagnosis of fetal aneuploidy
Fetal aneuploidy is not as common as other birth defects, affecting 9 in 1000 births and increasing with maternal age. Amniocentesis and chorionic villus sampling have historically been two of the most popular methods used to detect fetal aneuploidy. Since these procedures are invasive, they may...
testing methods based on the presence of fetal genetic material in maternal blood.
Types
| color | significance |
|---|---|
| lethal | |
| normal female phenotype | |
| normal male phenotype | |
| Turner's syndrome (abnormal female) | |
| Klinefelter's syndrome (abnormal male) | |
| 0 | X | XX | XXX | XXXX | XXXXX | |
|---|---|---|---|---|---|---|
| 0 | 00 | X0 | XX | XXX | XXXX | XXXXX |
| Y | Y0 | XY | XXY Klinefelter's syndrome Klinefelter syndrome, 46/47, XXY, or XXY syndrome is a condition in which human males have an extra X chromosome. While females have an XX chromosomal makeup, and males an XY, affected individuals have at least two X chromosomes and at least one Y chromosome... |
XXXY | XXXXY | XXXXXY |
| YY | YY | XYY XYY syndrome XYY syndrome is an aneuploidy of the sex chromosomes in which a human male receives an extra Y-chromosome, giving a total of 47 chromosomes instead of the more usual 46. This produces a 47,XYY karyotype... |
XXYY | XXXYY | XXXXYY | XXXXXYY |
| YYY | YYY | XYYY | XXYYY | XXXYYY | XXXXYYY | XXXXXYYY |
| YYYY | YYYY | XYYYY | XXYYYY | XXXYYYY | XXXXYYYY | XXXXXYYYY |
| YYYYY | YYYYY | XYYYYY | XXYYYYY | XXXYYYYY | XXXXYYYYY | XXXXXYYYYY |
| color | significance |
|---|---|
| case where complete non-mosaic trisomy can never survive to term | |
| case where complete non-mosaic trisomy can occasionally (barring other complications) survive to term | |
| case where complete non-mosaic trisomy can always (barring other complications) survive to term |
| # | monosomy | trisomy |
|---|---|---|
| 1 | Trisomy 1 | |
| 2 | Trisomy 2 | |
| 3 | Trisomy 3 | |
| 4 | Wolf-Hirschhorn syndrome Wolf-Hirschhorn syndrome Wolf–Hirschhorn syndrome , also known as chromosome deletion 4p syndrome, Pitt-Rogers-Danks syndrome or Pitt syndrome, was first described in 1961 by Americans Herbert L... |
Trisomy 4 |
| 5 | Cri du chat Cri du chat Cri du chat syndrome, also known as chromosome 5p deletion syndrome, 5p minus syndrome or Lejeune’s syndrome, is a rare genetic disorder due to a missing part of chromosome 5. Its name is a French term referring to the characteristic cat-like cry of affected children. It was first described by... 5q deletion syndrome |
Trisomy 5 |
| 6 | Trisomy 6 | |
| 7 | Williams syndrome Williams syndrome Williams syndrome is a rare neurodevelopmental disorder characterized by a distinctive, "elfin" facial appearance, along with a low nasal bridge; an unusually cheerful demeanor and ease with strangers; developmental delay coupled with strong language skills; and cardiovascular problems, such as... |
Trisomy 7 |
| 8 | Warkany syndrome 2 | |
| 9 | Trisomy 9 Trisomy 9 Trisomy 9 is a chromosomal disorder caused by having three copies of chromosome number 9. It can appear with or without mosaicism.-Characteristics:... |
|
| 10 | Trisomy 10 | |
| 11 | Jacobsen syndrome Jacobsen syndrome Jacobsen Syndrome, also known as 11q deletion disorder, is a rare congenital disorder resulting from deletion of a terminal region of chromosome 11 that includes band 11q24.1. It can cause intellectual disabilities, a distinctive facial appearance, and a variety of physical problems including heart... |
Trisomy 11 |
| 12 | Trisomy 12 | |
| 13 | Patau syndrome Patau syndrome Patau syndrome, also known as trisomy 13 and trisomy D, is a chromosomal abnormality, a syndrome in which a patient has an additional chromosome 13 due to a nondisjunction of chromosomes during meiosis. Some are caused by Robertsonian translocations... |
|
| 14 | Trisomy 14 | |
| 15 | Angelman syndrome Angelman syndrome Angelman syndrome is a neuro-genetic disorder characterized by intellectual and developmental delay, sleep disturbance, seizures, jerky movements , frequent laughter or smiling, and usually a happy demeanor.... Prader–Willi syndrome |
Trisomy 15 |
| 16 | Trisomy 16 Trisomy 16 Trisomy 16 is a chromosomal abnormality in which there are three copies of chromosome 16 rather than two. It is the most common chromosomal cause of miscarriage during the first trimester of pregnancy.... |
|
| 17 | Miller-Dieker syndrome Miller-Dieker syndrome Miller–Dieker syndrome , also called Miller–Dieker lissencephaly syndrome and chromosome 17p13.3 deletion syndrome, is an autosomal dominant congenital disorder characterized by a developmental defect of the brain, caused by incomplete neuronal migration.This syndrome should not be confused with... Smith-Magenis syndrome Smith-Magenis syndrome Smith–Magenis Syndrome is a developmental disorder that affects many parts of the body. The major features of this condition include mild to moderate mental retardation, distinctive facial features, sleep disturbances, and behavioral problems... |
Trisomy 17 |
| 18 | 18q deletion syndrome | Edwards syndrome Edwards syndrome Trisomy 18 is a genetic disorder caused by the presence of all or part of an extra 18th chromosome. It is named after John H. Edwards, who first described the syndrome in 1960... |
| 19 | Trisomy 19 | |
| 20 | Trisomy 20 | |
| 21 | Down syndrome Down syndrome Down syndrome, or Down's syndrome, trisomy 21, is a chromosomal condition caused by the presence of all or part of an extra 21st chromosome. It is named after John Langdon Down, the British physician who described the syndrome in 1866. The condition was clinically described earlier in the 19th... |
|
| 22 | DiGeorge syndrome DiGeorge syndrome 22q11.2 deletion syndrome, which has several presentations including DiGeorge syndrome , DiGeorge anomaly, velo-cardio-facial syndrome, Shprintzen syndrome, conotruncal anomaly face syndrome, Strong syndrome, congenital thymic aplasia, and thymic hypoplasia is a syndrome caused by the deletion of a... |
Cat eye syndrome Cat eye syndrome Cat Eye Syndrome is a rare condition caused by the short arm and a small section of the long arm of human Chromosome 22 being present three or four times instead of the usual two times. The term "Cat Eye" syndrome was coined because of the particular appearance of the vertical colobomas in the... Trisomy 22 Trisomy 22 Trisomy 22 is a chromosomal disorder in which there are three copies of chromosome 22 rather than two. It is a frequent cause of spontaneous abortion during the first trimester of pregnancy. Progression to the second trimester and livebirth are rare.This disorder is found in individuals with an... |