What happens whenthere is a chromosomal disorder? Accordingto Oxford dictionaries, “a Trisomy is a condition in which anextra copy of a chromosome is present in the cell nuclei, causing developmentalabnormalities.” Trisomy usually manifest itself duringmeiosis, which is upon the process of the eggs and sperm forming. In meiosis,the duplicate chromosomes are arranged into daughter cells in two steps, calledmeiosis I and meiosis II. Trisomy means that there are three copies of acertain chromosome instead of the usual pair of chromosomes. Most people know of a prominent Trisomy, called Down syndrome,however several types encircle human society today. In this paper the fivemost common types of autosomal trisomies in humans that survive to birth, otherwiseknown as Trisomy 8, Trisomy 9, Trisomy 13, Trisomy 18, and Trisomy 21, will bediscussed in this following review.First, there is Trisomy 8mosaicism syndrome Trisomy 8 that according to Health line is a condition thataffects human chromosomes.
People who have Trisomy 8 have three completecopies, (instead of the typical two) of chromosome eight in their cells. Theextra chromosome eight appears in some of the cells, but not all. The symptomsof this syndrome vary considerably, alternating from undetectable to, in somecases, severe. The condition is also called Warkany syndrome 2.Trisomy 8 is a rare disorder,affecting males more often than females at a ratio of 4-to-1, according to Health line.
Trisomy 8 isthought to occur in one out of every 25,000-50,000 pregnancies. The chances ofhaving more than one Trisomy 8 pregnancy are extremely low.Trisomy 8 is caused by a problembetween the sperm and egg in which some cells do not divide accurately.
Cellsdo not divide simultaneously, so chromosomes are not distributed properly as aresult. This process is called “non-disjunction.” Depending on when thenon-disjunction occurs during the baby’s development, the organs and tissuesaffected by extra chromosomes can differ. The condition is most commonly a accidentalincidence, but it is occasionally hereditary.Symptoms of Trisomy 8 differ significantly.Some children born with Trisomy 8 have severe, highly visible physical symptomswhile others show no visible symptoms.
Potential symptoms include: longer-than-averagehead, wide, deep eyes ,thick lips, large forehead, narrow shoulders ,long torso,narrow pelvis ,deep creases on the hands and feet, problems with the palate ormouth, joint problems and stiffness, spinal issues, such as scoliosis, kidneyproblems, heart issue, bone and structure abnormalities, underdevelopedgenitals, lack of intellectual development, extreme stature (either very shortor very tall).Sometimes Trisomy 8 does notaffect cerebral development. Intellectual development will be reliant, in manyways, on the health of the child during crucial development stages. Othersymptoms of Trisomy 8 may cause an infant to have speech or learning delays.But those delays are a result of the child’s physical limitations, not theirmental capabilities. Health line reports that often, children with Trisomy 8may “catch up” to their peers in speech and learning. There are cases whereindividuals with Trisomy 8 do not seem to have an intellectual impairment atall.
This illness frequently goesundiagnosed, because there may be no detectable symptoms. In cases where Trisomy8 is suspected in an infant the doctormay take a blood or skin sample and perform a cell analysis. This test does notdefine the severity of symptoms. Instead, it just describes whether Trisomy8 /”””””””””””””’ispresent.In most cases, a doctor diagnoses Trisomyduring pregnancy or early childhood.
There are now blood tests that woman cantake during pregnancy to determine whether the baby they are carrying is likelyto have Trisomy 8. If the doctor notices that the baby is measuring small, hasonly one artery in the umbilical cord, they will prescribe more testing for thebaby.Although there is no cure for Trisomy8, some symptoms of the condition may be treated. Treatment will contrastdepending on symptoms and severity. Symptoms with no associated healthproblems, such as facial deformities, may be difficult to treat and may requiresurgery. In some cases, heart surgery is also recommended. A surgeon can oftencorrect palate problems.
This will help address any speech delay or impairment.If most or all cells have theextra chromosome, the condition is known as full or complete Trisomy 8. Full Trisomy8 is fatal, often leading to miscarriage in the first trimester of pregnancy.People with only some of the cells affected canlive normal lifespans, as long as other complications from the disorder do notdevelop.Second,there is Trisomy 9, Mosaicism syndrome, is a chromosomaldisorder where some of the body’s cells have three copies of chromosome9 (Trisomy), while other cells have the typical twocopies of this chromosome. Most casesare not inherited; it often occurs as a random event during the creation of thereproductive cells (egg and sperm) or as the egg that was fertilized divides. An error in celldivision (called nondisjunction) may cause some eggs or sperm to have anirregular numberof chromosomes. If an egg or sperm with an additional chromosome 9 adds to thegenetic character of an embryo, the embryo willhave an extra copy of chromosome 9 in each cell.
Ininfrequent cases, mosaic Trisomy 9 may be inherited from a parent with a chromosomalrearrangement that occurs when a segment of chromosome 9 has broken off in twoplaces, rotated around 180 degrees and reinserted itself into the chromosome.In these cases, the parent has a stable rearrangement, since the chromosome isin a different order but no genetic material is gained or lost. Carriers of abalanced rearrangement typically to not have any symptoms or health problems. Thesigns and symptoms of mosaic Trisomy 9 differ but may include: abnormal growthincluding low birth weight, short stature, unusually small head, a slopingforehead with narrow temples; a broad nose, a small jaw; cleftlip and/or palate; low-set ears; unusually small eyes,upwardly slanting eyelid folds. Brainmalformations, mild to severe intellectual disability and developmental delay, congenitalheart defects, and vision problems, irregularities of the muscles and bones ,undescended testes, and kidney problems.SometimesTrisomy 9 can be diagnosed before birth, by an ultrasound. Other tests, such as chorionic villus sampling (CVS)or an amniocentesis, fluid or tissue sample is used in order to get a pictureof the baby’s chromosomes. In other cases, the child is not diagnosed untilafter birth through physical exam or a blood sample.
Asthe embryo grows and divides, an attempt may be made to correct the mistake byeliminating one extra chromosome 9. However, this attempt may be sometimes unsuccessful,leaving some cells with an extra chromosome 9 and some cells with the extrachromosome erased. Children with bone ormuscle abnormalities or delayed motor milestones might be referred for physicalor occupational therapy.
Specialeducation classes can be given for intellectual disability. Heart defectsand cleft lip and/or palateare usually surgically repaired. Theprognosis for people with mosaic Trisomy 9 largely depends on the degree towhich the condition has affected any major organs, such as the heart and/orbrain. Some people affected by mosaic Trisomy 9, some of the body’s cells havethe usual two copies of chromosome 9, while other cells have three copies of Trisomy9.
The percentage of cells with Trisomy 9 and which parts of the body areaffected vary from person to person. Third,Trisomy 13, which is also called Patau syndrome, is a type of chromosomedisorder classified by having three copies of chromosome 13 in cells of thebody, instead of the usual two copies. In some affected people, only a portionof cells contains the extra chromosome 13, which is called mosaicTrisomy 13, while other cells contain the normal chromosome pair. Mosaic Patau syndrome is not inherited.In rare cases, the extra material can be attached to another chromosome, whichis called translocation. People with this disease usually have severe cerebralincapacity and physical deformities in several parts of the body.Peoplewho have Trisomy 13 often have weak muscletone, heart defects, very small or poorly developed eyes, an opening in thelip, with or without an opening in the roof of the mouth, brain or spinal cordabnormalities, extra toes or fingers, and babies have trouble feeding ordigesting food.
Babies often have low birth weight due to Trisomy 13.Doctorsusually diagnose babies by fetal ultrasounds during the first trimester of apregnancy. There are many screening tests, such as cell-free DNA screening orthe pregnancy-associated plasma protein A. Other tests that are more certainare a chorionic villus sampling or amniocentesis.Thereis no cure for Trisomy 13; however, doctors focus treatment on the patient’ssymptoms. Patients are given therapy and even surgery to correct abnormalities.
Each patient’s situation may vary.Sinceinfants with this disease may have several life-threatening medical problems,many infants with Trisomy 13 die within theirfirst days or weeks of life. Newborns that have this disease have to combatpneumonia, seizures, congenital heart defects, and breathing difficulties.According to WebMD, more than 80% of babies do not survive from this disease.As a result, only five percent to 10 percent of children with this conditionlive past their first year.Anothertype of Trisomy is Trisomy 18.
Accordingto WebMD, Trisomy 18 is also called Edwards syndrome, per the doctor who firstdescribed this disease. Trisomy 18, like the other trisomies, has three copiesof extra chromosome. Instead of having a total of 46 chromosomes, numbereighteen is tripled. The extra chromosomes can come from either the father orthe mother of the fetus. Three types of Trisomy 18 are full Trisomy 18, partialTrisomy 18, and mosaic Trisomy 18(either the extra chromosome is in all of thecells, part of the cells or is in only some of the baby’s cells).Symptomsinclude: deformed feet, low-set ears, cleft palate, clenched fists withoverlapping fingers, and defects of the heart, lungs, kidneys and intestines.
There is also severe developmental delays, slowed growth. Newborns can have asmall head, small jaw, weak cry, and have problems with feedings.Inorder to diagnose, the doctor may check during pregnancy ultrasound.Ultrasounds are not as accurate as other tests. Thus, the doctor may recommendchecking the cells by an amniocentesis or placenta (chorionic villus sampling).
Some parents may elect to have a chromosome blood test after giving birth whichwould report the likelihood of having another baby with the same disorder. The doctor may also recommend mothers to see agenetic counselor. Treatment is aimed at correcting the symptoms with therapyor surgery.Accordingto Stanford Children’s Health, there are few reports stating that babiessurvive to their teens with this disease, but it is rare. The majority ofbabies born with Trisomy 18 die by their first birthday.
A handful of patientslive well into their 20s and 30s. Moreover, Trisomy 21, also known asDown syndrome, is the most common type of genetic disorders. Down syndrome wasdiscovered in 1866 and named after Dr.
John Langdon, who first discovered it.Just like the other trisomies, Trisomy 21 has three copies instead of the usualpair. According to the National Down Syndrome Society, there are more than350,000 people living with Down syndrome in the United States. Thereare three types of Down syndrome and each have a different cause. First, there isTrisomy 21, which causes most cases. When the egg and the sperm unite to formthe fertilized egg, three instead of two chromosomes 21 are present. As thecells divide the extra chromosome is repeated in every cell.
Next, there ismosaic Trisomy 21, a rare form of Down syndrome, in which the extra chromosome21 is present in some, but not all cells of the patient. Abnormal cell divisionhappens after fertilization. The third type is Translocation Trisomy 21, wherepart of chromosome 21 becomes attached (translocated) to another chromosome(usually the 13th, 14th or 15th chromosome). Translocation can happen before orat conception. Symptomsinclude slanting eyes, small mouth, short neck, flat face, low muscle tone.
People will also have small ears and below average intelligence. These symptomsare for most people living with Down syndrome. Todiagnose Down syndrome, doctors use screening tests, diagnostic tests, andblood test and physical exams.
Sometimes they test both the mother and thebaby’s blood. The results for these diagnostic tests could take could take upto 2 to 3 weeks. Treatmentfor Down syndrome is aimed at the symptoms. Some children with Down syndromeare provided physical and speech therapy. Adults that have Down syndrome areoffered occupational therapy in order to acquire skills to live on their own.Counseling may be offered to help with emotional issues and blending intosociety. Inthe past people with Down syndrome mainly lived up to nine years old. Accordingto Medicine net, people with Down syndrome can now live up to 50 years andmore.
Things have changed drastically for people living with Down syndrome. Eventhough most people know of one Trisomy such as Down syndrome, we now know thatthere are several. Each Trisomy has similarities and differences. Knowledge ispower.
When we have more information on a disease then we can understand iteven more. References