Mosaic Down Syndrome

Mosaic Down Syndrome: What Is It?

The term mosaic refers to a collection of different genetic variations. A person with mosaic Down syndrome (MS) may have one or several copies of certain genes while having no other symptoms. Some people with MS are carriers of two copies of the same gene, but they do not show any signs or symptoms. Others with mosaic Down syndrome have only one copy of the gene, but they still carry some risk factors for developing MS. People with mosaic Down syndrome are at increased risk for many diseases including heart disease, stroke, cancer and autoimmune disorders such as multiple sclerosis.

How Common Is Mosaic Down Syndrome?

There is no exact number on how common mosaic Down syndrome is in the general population. However, it is estimated that there are between 1 in 1000 and 1 in 5000 people worldwide with mosaic Down syndrome. The prevalence of mosaic Down syndrome varies from country to country. There are also differences among ethnic groups within countries. For example, the rate of MS is higher in African Americans than Caucasians. Therefore, it is possible that the rates of MS may be lower in African American populations compared to Caucasian populations due to their genetic makeup being more similar to each other than Caucasians’.

Causes of Down Syndrome

Chromosomes are the structures that contain the genes you inherit from your parents. Normally, people have 46 chromosomes, which include 22 pairs of autosomes (the same for males and females) and two separate gender-determining chromosomes, the XX pair in females and the XY pair in males. A baby’s genetic material is contained within reproductive cells called gametes, which are either eggs or live. When an egg from the mother unites with a live from the father, the child has a total of 46 chromosomes, which are split equally between the mother and father, resulting in 23 pairs.

A pair of chromosomes contains genes, which are units that determine physical traits, behavior and other characteristics of an individual. The human mind has over 20,000 genes, which are made up of nucleobases and amino acids. It is possible for genes to be different from person to person. The 23rd pair of chromosomes, the pair that contains the genes that determine if a fetus will develop or not, is very unique and specific to each individual.

This pair is called the “sexual determination chromosome.” Normally it takes a combination of an X and a Y chromosome (XY) for a male fetus to develop. A combination of two X’s (XX) will result in the development of a female fetus. An error in cell division, which separates the 23rd pair of chromosomes when it should not, can result in a female having an extra X (XXY), or a male having two X’s (XXXY). This combination of an extra or double X or Y chromosome is called Klinefelter syndrome. A female with Klinefelter syndrome will appear typically female and have some masculine traits. A male with Klinefelter syndrome will have a small stature and have some female physical traits. It is believed that this type of chromosomal abnormality occurs in up to half of all miscarriages.

It is also possible for a female to have three copies of the X chromosome (triple X, or Trisomy X), or a male to have two copies of the Y chromosome (double Y, or Duane syndrome). The effects of having three copies of the X or two copies of the Y are similar. Males will have severe mental retardation and die within a year after birth. Females rarely live past infancy, but those who do survive tend to have severe physical deformities and die before reaching puberty.

Down syndrome occurs when there is an extra copy of the 21st chromosome in a child (hence the abbreviation Trisomy 21), which is a complete accident. The extra copy results in a child having three copies of the genes on the 21st chromosome, which is why they have an extra marker. This syndrome occurs in approximately 1 out of every 700 to 1200 births in the United States, and usually results in miscarriage. However, when this occurs in the fetus, it can survive birth.

A child born with Down Syndrome will have a distinct facial appearance and form, which can be used to identify them as having the syndrome.

Down Syndrome is caused by an error in cell division called nondisjunction. When a parent passes on genes to their offspring, they must split a set of chromosomes in half to create reproductive cells, which in turn are used to create the baby. Normally, each reproductive cell will have 23 pairs of chromosomes (22 pairs of regular chromosomes and one pair of sexual determination chromosomes). Each pair will have one chromosome inherited from the mother and another inherited from the father.

When nondisjunction occurs, a reproductive cell is created with either three chromosomes inherited from the mother or three chromosomes inherited from the father (this could be a total of three maternal chromosomes or a total of three paternal chromosomes).

A fetus with Trisomy 21 has an extra copy of all the genes on the 21st chromosome, which results in abnormality. The extra copy results in abnormality. The exact nature of the abnormality is unknown, but it is obvious to the human eye. In addition, individuals with Down Syndrome tend to have certain similarities in their personalities and in other traits.

These similarities are what lead to the “Mongoloid slant” of the eyes, or epicanthic folds that most people with Down Syndrome have.

The cause of Down Syndrome is not known. It is believed to be due to an error in cell division during early development. While most babies that have this syndrome die during miscarriage, there is currently no way to detect if a mother will have a child with this syndrome before birth. At least some of the time, it appears that women who miscarry a pregnancy with this syndrome will not be able to have another child, although other women have been known to carry children with the syndrome to term.

It isn’t known if having a child with the syndrome increases or decreases the odds of having another child with the syndrome. It does appear that women under the age of 20 are at a higher risk for having a child with the syndrome, as well as women over the age of 35.

Recent studies have shown that children with Down Syndrome do not have an increased possibility of bearing children with the syndrome. It appears that this is a random and rare occurrence.

Children born with Down Syndrome have a normal life span, although special care and education will be necessary. With proper training and care, children with Down Syndrome can learn to communicate, to the point where they can effectively express wants and needs. The extent of their learning and abilities is limited by the capacity of their minds.

Children with Down Syndrome can learn enough to lead relatively independent lives, although they will always require an amount of supervision and care that many parents are unable or unwilling to provide.

Hereditary diseases are a fact of life, and eugenics programs have eliminated many deadly and debilitating conditions from most societies in this world. Still, many people are born with defects that make life difficult if not impossible. Some of these conditions have no treatment or cures, and some of them can’t even be detected before birth. This page will examine some of the more common hereditary diseases.

Achondroplasia is a relatively common form of dwarfism that generally leads to a shorter than average life span, but does not appear to cause any major medical problems. Most infants that have this condition are born to normal sized parents, and the condition tends to lower the general health of the parents, making them more susceptible to disease.

Alinejad Syndrome is a relatively rare condition that causes extreme abnormalities in physical and mental development. Most infants born with this condition do not live for more than a few hours after birth, although some have lived for a few days before dying. There are no known cases of children living past the age of two.

Andersen’s Syndrome is a relatively common form of dwarfism. Most infants with this condition are born to normal sized parents, and the condition tends to lower the general health of the parents, making them more susceptible to disease.

Asperger’s Syndrome causes developmental problems with children that generally become noticeable when they hit school age. While mildly retarded children can be distinguished from others by their behavior or learning abilities, children with Asperger’s Syndrome will often have advanced knowledge in some subjects and difficulty in others. In extreme cases, some children with this condition never learn to speak.

Autism is a common problem that many children have. For most, the condition is relatively mild and can be overcome with early treatment. Other children suffer from more severe forms of the disease, making communication and socialization extremely difficult if not impossible.

Down Syndrome occurs as a result of an extra chromosome in a child’s genetic composition. While this condition does not always lead to severe mental retardation, it is almost always a guarantee. Children born with this condition are also prone to a variety of different diseases and health issues throughout their lives. It is for this reason that most parents who know their child has Down Syndrome prior to birth choose to have an abortion.

Prader-Willi Syndrome causes severe lack of muscle development and other abnormalities in the deveolpment of a child’s body. Most infants with this condition tend to be slightly shorter than average, and suffer from poor muscle tone throughout their lives. Children with this condition usually have smaller frames and weak bone structures, making them prone to breaking bones easier than others and lacking the strength to perform common, everyday tasks.

Williams Syndrome causes developmental problems in a child’s mental growth. While most children learn to talk at certain points in their lives, children with Williams Syndrome typically do not begin speaking until much later, if at all.

Sources & references used in this article:

Survival of children with mosaic Down syndrome by M Shin, C Siffel, A Correa – Am J Med Genet A. A, 2010 – academia.edu

The origin of mosaic Down syndrome: four cases with chromosome markers. by N Niikawa, T Kajii – American journal of human genetics, 1984 – ncbi.nlm.nih.gov

Accuracy of the clinical diagnosis of Down syndrome. by L Devlin, PJ Morrison – The Ulster medical journal, 2004 – ncbi.nlm.nih.gov

Mosaic Down syndrome in a patient with low‐level mosaicism detected by microarray by E Leon, YS Zou, JM Milunsky – American Journal of Medical …, 2010 – Wiley Online Library

… after intracytoplasmic sperm injection using round-headed spermatozoa and assisted oocyte activation in a globozoospermic patient with mosaic Down syndrome by ST Kim, YB Cha, JM Park, MC Gye – Fertility and sterility, 2001 – Elsevier

Mental development in Down syndrome mosaicism. by K Fishler, R Koch – American Journal on Mental Retardation, 1991 – psycnet.apa.org

Ophthalmic manifestations of mosaic Down syndrome by WW Motley III, DP Saltarelli – Journal of American Association for Pediatric …, 2011 – Elsevier

Transient leukemia followed by megakaryoblastic leukemia in a child with mosaic Down syndrome by JJ Doyle, P Thorner, A Poon, K Tanswell… – Leukemia & …, 1995 – Taylor & Francis