Familial Down Syndrome Is a Result of Which of the Following?
What is Down Syndrome?
In every prison cell in the human body in that location is a nucleus, where genetic cloth is stored in genes. Genes carry the codes responsible for all of our inherited traits and are grouped along rod-like structures called chromosomes. Typically, the nucleus of each cell contains 23 pairs of chromosomes, half of which are inherited from each parent. Down's syndrome occurs when an private has a full or partial extra copy of chromosome 21.
This additional genetic cloth alters the class of development and causes the characteristics associated with Down syndrome. A few of the mutual physical traits of Down syndrome are low musculus tone, modest stature, an upward slant to the eyes, and a single deep pucker beyond the centre of the palm – although each person with Down syndrome is a unique individual and may possess these characteristics to different degrees, or not at all.
How Common is Down Syndrome?
According to the Centers for Affliction Control and Prevention, approximately one in every 700 babies in the U.s. is born with Down syndrome, making Down's syndrome the most common chromosomal condition. About six,000 babies with Down's syndrome are born in the The states each yr.
When Was Down Syndrome Discovered?
For centuries, people with Downwardly syndrome accept been alluded to in art, literature and science. It wasn't until the late nineteenth century, however, that John Langdon Downwards, an English physician, published an accurate clarification of a person with Down syndrome. It was this scholarly work, published in 1866, that earned Down the recognition as the "father" of the syndrome. Although other people had previously recognized the characteristics of the syndrome, it was Downwardly who described the condition as a distinct and separate entity.
In contempo history, advances in medicine and science accept enabled researchers to investigate the characteristics of people with Down's syndrome. In 1959, the French physician Jérôme Lejeune identified Down's syndrome as a chromosomal condition. Instead of the usual 46 chromosomes present in each cell, Lejeune observed 47 in the cells of individuals with Down syndrome. Information technology was later determined that an extra partial or whole re-create of chromosome 21 results in the characteristics associated with Downwards syndrome. In the year 2000, an international team of scientists successfully identified and catalogued each of the approximately 329 genes on chromosome 21. This accomplishment opened the door to great advances in Down's syndrome research.
Are There Different Types of Down syndrome?
TRISOMY 21 (NONDISJUNCTION)
Down's syndrome is usually caused by an error in cell division called "nondisjunction." Nondisjunction results in an embryo with three copies of chromosome 21 instead of the usual 2. Prior to or at conception, a pair of 21st chromosomes in either the sperm or the egg fails to carve up. Every bit the embryo develops, the actress chromosome is replicated in every prison cell of the body. This type of Downwardly syndrome, which accounts for 95% of cases, is called trisomy 21.
MOSAICISM
Mosaicism (or mosaic Down syndrome) is diagnosed when at that place is a mixture of two types of cells, some containing the usual 46 chromosomes and some containing 47. Those cells with 47 chromosomes comprise an extra chromosome 21.
Mosaicism is the least common grade of Down's syndrome and accounts for only about 1% of all cases of Down syndrome. Enquiry has indicated that individuals with mosaic Down syndrome may have fewer characteristics of Downwardly syndrome than those with other types of Downwardly syndrome. All the same, broad generalizations are non possible due to the wide range of abilities people with Down syndrome possess.
TRANSLOCATION
In translocation, which accounts for about 4% of cases of Down syndrome, the total number of chromosomes in the cells remains 46; however, an additional full or partial re-create of chromosome 21 attaches to another chromosome, usually chromosome fourteen. The presence of the actress total or fractional chromosome 21 causes the characteristics of Downwardly syndrome.
What Causes Down's syndrome?
Regardless of the type of Down's syndrome a person may take, all people with Down syndrome have an extra, disquisitional portion of chromosome 21 present in all or some of their cells. This additional genetic material alters the grade of development and causes the characteristics associated with Down's syndrome.
The cause of the extra total or partial chromosome is still unknown. Maternal age is the only cistron that has been linked to an increased take a chance of having a baby with Down's syndrome resulting from nondisjunction or mosaicism. However, due to higher birth rates in younger women, 80% of children with Downwards syndrome are born to women under 35 years of age.
There is no definitive scientific research that indicates that Down syndrome is caused by ecology factors or the parents' activities before or during pregnancy.
The additional partial or full re-create of the 21st chromosome which causes Down's syndrome tin originate from either the father or the female parent. Approximately five% of the cases have been traced to the male parent.
Does Down Syndrome Run in Families?
All 3 types of Downwardly syndrome are genetic atmospheric condition (relating to the genes), but but one% of all cases of Down syndrome have a hereditary component (passed from parent to child through the genes). Heredity is not a factor in trisomy 21 (nondisjunction) and mosaicism. Withal, in one-third of cases of Down syndrome resulting from translocation there is a hereditary component – accounting for virtually 1% of all cases of Down's syndrome.
The age of the mother does not seem to be linked to the gamble of translocation. Most cases are desultory – chance – events. However, in almost one-third of cases, one parent is a carrier of a translocated chromosome.
What Is the Likelihood of Having a Second Child with Down's syndrome?
Once a adult female has given nascence to a infant with trisomy 21 (nondisjunction) or translocation, it is estimated that her chances of having another baby with trisomy 21 is one in 100 up until age 40.
The risk of recurrence of translocation is nigh 3% if the father is the carrier and x-15% if the mother is the carrier. Genetic counseling tin can determine the origin of translocation.
How Is Down syndrome Diagnosed?
PRENATALLY
There are 2 categories of tests for Down syndrome that can be performed before a baby is born: screening tests and diagnostic tests. Prenatal screens estimate the adventure of the fetus having Down syndrome. These tests exercise not tell you for certain whether your fetus has Down syndrome; they only provide a probability. Diagnostic tests, on the other paw, tin provide a definitive diagnosis with near 100% accuracy.
There is an all-encompassing carte du jour of prenatal screening tests now bachelor for significant women. Near screening tests involve a blood examination and an ultrasound (sonogram). The claret tests (or serum screening tests) measure quantities of various substances in the blood of the female parent. Together with a woman's historic period, these are used to estimate her chance of having a kid with Down syndrome. These claret tests are often performed in conjunction with a detailed sonogram to bank check for "markers" (characteristics that some researchers experience may accept a significant association with Downwards syndrome). New advanced prenatal screens are at present able to find chromosomal fabric from the fetus that is circulating in the maternal claret. These tests are not invasive (like the diagnostic tests below), merely they provide a high accuracy charge per unit. Nevertheless, all of these screens will non definitively diagnose Down syndrome. Prenatal screening and diagnostic tests are now routinely offered to women of all ages.
The diagnostic procedures available for prenatal diagnosis of Down's syndrome are chorionic villus sampling (CVS) and amniocentesis. These procedures, which carry upwards to a 1% risk of causing a spontaneous termination (miscarriage), are about 100% accurate in diagnosing Down syndrome. Amniocentesis is usually performed in the second trimester between xv and 20 weeks of gestation, CVS in the first trimester betwixt 9 and 14 weeks.
AT Nascency
Down syndrome is commonly identified at birth by the presence of certain physical traits: low musculus tone, a unmarried deep crease across the palm of the hand, a slightly flattened facial profile and an upward slant to the eyes. Because these features may be present in babies without Down syndrome, a chromosomal analysis chosen a karyotype is done to confirm the diagnosis. To obtain a karyotype, doctors depict a blood sample to examine the babe's cells. They photograph the chromosomes and so grouping them by size, number, and shape. By examining the karyotype, doctors can diagnose Down syndrome. Another genetic test chosen FISH can use like principles and ostend a diagnosis in a shorter amount of time.
Preferred Language Guide
Use this language when referring to Down's syndrome and people who have Down's syndrome:
- People with Down's syndrome should always be referred to as people commencement.
- Instead of "a Down syndrome child," it should be "a child with Downward syndrome." Also avoid "Down's kid" and describing the condition as "Down's," as in, "He has Down'south."
- Down syndrome is a condition or a syndrome, not a illness.
- People "have" Down syndrome, they do not "suffer from" it and are non "afflicted by" it.
- "Typically developing" or "typical" is preferred over "normal."
- "Intellectual disability" or "cognitive disability" has replaced "mental retardation" as the appropriate term.
- NDSS strongly condemns the use of the discussion "retarded" in any derogatory context. Using this word is hurtful and suggests that people with disabilities are not competent.
Downwards vs. Down'south
- NDSS uses the preferred spelling, Down syndrome, rather than Down syndrome.
- Down's syndrome is named for the English medico John Langdon Down, who characterized the condition, only did not accept it. An "apostrophe s" connotes ownership or possession.
- While Down syndrome is listed in many dictionaries with both popular spellings (with or without an apostrophe s), the preferred usage in the United States is Down syndrome. The AP Stylebook recommends using "Downwards syndrome," as well.
These downloadable versions of the Preferred Language Guide are available to print and distribute:
- NDSS Preferred Linguistic communication Guide
- NDSS Fact Canvass and Language Guide
Resources
EXTERNAL RESOURCES
- Brighter Tomorrows
www.brightertomorrows.org
Brighter Tomorrows is a web-based resource for parents who have received a diagnosis of Down syndrome either prenatally or at birth. The site provides answers to common questions, educates virtually Down Syndrome and shares the stories of other parents with similar situations. - Down syndrome Pregnancy
www.downsyndromepregnancy.org
This site provides information and support to expectant parents preparing for the birth of a baby with Down's syndrome.
- International Mosaic Down Syndrome Association
www.imdsa.org
Offers support and resources to families of and individuals with mosaic Down syndrome through the lifespan
- Medline Plus: Health Topics – Down's syndrome
www.nlm.nih.gov/medlineplus/downsyndrome.html
An overview and list of resources on Down syndrome and prenatal testing from Medline Plus, a service of the United states of america National Library of Medicine and the National Institutes of Health
- National Social club of Genetic Counselors
www.nsgc.org
Find members of NSGC through the Find A Genetic Advisor search function
- Understanding a Down's syndrome Diagnosis
www.lettercase.org
Understanding a Down syndrome Diagnosis is an authentic, balanced and up-to-date booklet for employ when delivering a diagnosis of Down Syndrome. It is bachelor as a free e-book from Lettercase.
DVDS
- Down's syndrome: The Offset 18 Months. Blueberry Shoes Productions.
BOOKS
- A Parent's Guide to Down Syndrome: Toward A Brighter Futurity. Pueschel, S. (2000). Baltimore, Doctor: Brookes Publishing.
- Babies with Down syndrome: A New Parents' Guide (3rd Edition). Skallerup, S. (Ed.) Bethesda, MD: Woodbine Business firm. (2008)
- Downs: The History of a Disability. Wright, D. New York, NY: Oxford University Press. (2011)
- Tales of Normansfield: The Langdon Down Legacy. Merriman, A. Beccles, UK: The Downwards's Syndrome Association. (2007)
- The Guide to Skilful Health for Teens and Adults with Down Syndrome. McGuire, D. and Chicoine, B. Bethesda, Doc: Woodbine House. (2010)
Source: https://www.ndss.org/about-down-syndrome/down-syndrome/
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