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Most chromosome abnormalities occur as an accident in the egg cell or sperm, and therefore the anomaly is present in every cell of the body. Some anomalies, however, can happen after conception, resulting in Mosaicism (where some cells have the anomaly and some do not). Chromosome anomalies can be inherited from a parent or be "de novo". This ...
The following is a list of genetic disorders and if known, type of mutation and for the chromosome involved. Although the parlance "disease-causing gene" is common, it is the occurrence of an abnormality in the parents that causes the impairment to develop within the child. There are over 6,000 known genetic disorders in humans.
Complete trisomy 8 causes severe abnormalities in the developing fetus and can be a cause of miscarriage. [2] [3] Complete trisomy 8 is usually a gestational lethal condition, whereas trisomy 8 mosaicism is less severe and individuals with a low proportion of affected cells may exhibit a comparatively mild range of physical abnormalities and developmental delay. [4]
The extra chromosome 21 material may also occur due to a Robertsonian translocation in 2–4% of cases. [91] [101] In this translocation Down syndrome, the long arm of chromosome 21 is attached to another chromosome, often chromosome 14. [102] In a male affected with Down syndrome, it results in a karyotype of 46XY,t(14q21q).
Trisomy 18 is a chromosomal abnormality characterized by the presence of an extra copy of genetic material on the 18th chromosome, either in whole (trisomy 18) or in part (such as due to translocations). The additional chromosome usually occurs before conception. The effects of the extra copy vary greatly, depending on the extent of the extra ...
Triploidy can result from either two sperm fertilizing one egg (60%) or from one sperm fertilizing an egg with two copies of every chromosome (40%). [2] These are otherwise known as diandric fertilization and digynic fertilization. Pregnancies caused by digynic fertilization are more likely to end right before a baby is due for full term.
Intellectual disabilities range from very mild to very severe, and can co-occur with behavioral disorders and/or autism spectrum disorders. [3] At birth, the main symptoms include low weight (due to intrauterine growth restriction), hypotonia, and feeding difficulties. Infants may also have cleft palate. [3]
We will explore chromosome specific cases in the chromosome specific section. Type of chromosome abnormality: The factor that had the highest predictive value as to whether the fetus was affected or not was the type of chromosome abnormality. Marker chromosomes were more often confirmed in the fetus than trisomies.