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Chromosomal aberration definition
Chromosomal aberration is a condition in which deletion or duplication of a particular chromosome in a set, lead to monosomy, nullisomy, trisomy, tetrasomy. Some disorders in human being due to chromosomal aberrations are as follows:
Klinefelter syndrome (XXY)
It is due to a trisomic condition in sex chromosomes, a person has XXY chromosomes. It’s chromosomal variation in males with an extra X chromosome, these extra chromosomes can affect physical, developmental, behavioral, and cognitive functioning. The affected person may develop hypogonadism (small testes), delay in pubertal development and lack of secondary male sexual characters, and may also develop gynecomastia (breast growth). It is not inherited but develops randomly due to non-disjunction error during meiosis in mother or father (egg with XX chromosomes or sperm with XY chromosomes). This condition occurs in about 1 in 500-1000 males. An affected child can’t diagnose at birth due to lack of any abnormal or dysmorphic feature, identification takes place with pre-natal detection or when they don’t develop puberty.
Turner syndrome (XO)
It is due to monosomy in sex chromosomes, a person has XO condition. The affected person is female with single X chromosomes (absence of one X chromosomes), there is absence of Barr body. This condition is very rare 1 in 5000-10000. At birth some time baby look like normal, prenatal detection diagnose this condition, symptom appear with increasing age
Triple X syndrome (XXX)
Female with one extra X chromosomes has triple X syndrome. This is a trisomic condition in sex chromosomes in 95% cases it is due to non-disjunction during oogenesis. About 0.1% of all females have XXX syndrome. There is the presence of one extra Barr body. Women usually have a normal physical appearance, but can have a mild reduction in intellectual skill between 10-20 points. They are fertile and have children with normal karyotypes.
This is due to the presence of one extra Y chromosomes (trisomic condition), with karyotype 47XYY. Affected persons are taller than normal, sometimes they are more aggressive in nature due to an extra Y chromosome.
Fragile X Syndrome
This should be classified as a single gene disorder rather than a chromosomal aberration, in this X chromosome is fragile at the telomere of a long arm, mainly male are affected, females are generally carrier. Affected males have a problem in learning.
This is due to trisomy in 21 pairs of chromosomes. Affected persons have a moon-like face, small ear, protruding tongue, about 40-50% of babies with down syndrome have congenital heart. Frequency is approximately 1 in 1000 in the UK
Baby with Edward syndrome has trisomy in chromosomes 18. It occurs in a 1:5000 ratio. They have some level of learning disability, may have heart disease, respiratory, kidney, or gastrointestinal condition. The extra chromosome is maternal in origin in most of the cases of Edwards syndrome.
It is due to trisomy in chromosomes 13. Frequency is about 1 in 5000. Facial appearance shows severe bilateral cleft in lip and palate. In most of the cases of additional chromosomes is maternal in origin
It is due to the deletion of the short arm of 5 chromosomes. In this syndrome child cry like the cat that’s why it is called a cri-du-chat syndrome. The cat-like voice is due to problems in with larynx and nervous system. Frequency is about 1 in 20,000-50,000.
References and Sources
- Element of medical genetics by Peter Turnpenny and Sian Ellard
- 2% – https://rarediseases.org/rare-diseases/xyy-syndrome/
- 1% – https://www2.palomar.edu/anthro/abnormal/abnormal_5.htm
- 1% – https://www.spectrumnews.org/news/deletion-duplication-chromosome-16-segment-may-confer-autism-risk/
- 1% – https://www.sciencedirect.com/topics/neuroscience/down-syndrome
- 1% – https://www.nhs.uk/conditions/downs-syndrome/how-to-help-children-and-young-people/
- 1% – https://raisingchildren.net.au/guides/a-z-health-reference/cri-du-chat-syndrome
- 1% – https://quizlet.com/24801989/5-cytogenetics-flash-cards/
- 1% – https://quizlet.com/144844751/heredity-and-genetics-flash-cards/
- 1% – https://en.wikipedia.org/wiki/XYY_syndrome