Turners syndrome is a sex chromosome abnormality in which the phenotypic appearing female offspring is missing an X-chromosome and therefore has a genotype of 45 X as opposed to the normal female which is 46 XX. Females with Turners syndrome have only vestigial ovaries and low production of estrogen and progesterone. They are short in stature and other physical characteristics include presence of a webbed neck and lymphedema of the hand and feet at birth.
Chromosomal Disorders
The human body has 23 pairs of chromosomes: 22 pairs of autosomes and 1 pair of sex chromosomes. This gives humans 46 chromosomes in total. Every chromosome contains hundreds to thousands of your genes. Genes provide instructions for building proteins that help bodies grow and function properly.
Chromosomal genetic disorders occur when chromosomes are partially or completely missing, altered or duplicated. An example of a chromosomal genetic disorder is Down syndrome. Down syndrome is the result of an extra, third copy of chromosome 21 being present in a person. This extra chromosome results in extra protein production and upsets the body’s balanced systems.
During pregnancy chromosomal abnormalities can cause the death of an embryo or fetus. Chromosomal disorders can result in mental retardation or other developmental problems. Older pregnant women have a higher risk of passing on chromosomal genetic disorders.
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Klinefelter’s syndrome is a genetic disorder found in males and affects male sexual development. Males normally have a total of 46 chromosomes; one X and one Y chromosome (46-XY). However, males with Klinefelter’s syndrome have an extra X chromosome (47-XXY) and therefore a total of 47 chromosomes.
The presence of an extra X chromosome primarily affects the testes. Males with this condition typically have small testes that do not produce enough testosterone, which is the hormone that directs male sexual development before birth and during puberty. A shortage of testosterone during puberty can lead to breast enlargement (gynecomastia), reduced facial and body hair, and an inability to father children (infertility). Older children and adults with Klinefelter's syndrome tend to be taller than other males their age. Compared with other men, adult males with Klinefelter's syndrome have an increased risk of developing breast cancer and chronic inflammatory diseases such as systemic lupus erythematosus. Their chance of developing these disorders is similar to that of normal adult females. Boys with Klinefelter's syndrome may have learning disabilities and difficulty with speech and language development.
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See All 2 AnswersIn humans, chromosomes contain the genetic information that makes us who we are. In general, human beings have 23 sets of chromosomes or 46 total, one set from each parent. The chromosomes are contained in all of our cells and are constantly being copied to produce more cells. However, this process does not occur without mistakes but our body had inherent mechanisms to detect mistakes and correct them. But from time to time, mistakes do go uncorrected. When this happens, this can lead to various diseases such as Down's syndrome, chronic lymphocytic leukemia, etc. There are various mistakes that can occur with this copying of our chromosomes such as: a section of the chromosome is duplicated, deleted, a part of a chromosome can break off and attach to another. This events are called chromosomal abnormalities. This is what geneticists look for when doing genetic counseling as certain diseases have linked to specific chromosomal abnormalities that can be discovered when doing genetic testing.
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See All 2 AnswersChromosomal disorders are generally caused by mutations that affect a specific chromosome. Typically, these types of disorders are not inherited but are more likely random genetic errors that occur during the reproductive process. During cell division, a developing infant's body can mistakenly produce extra chromosomes or accidentally produce too few chromosomes. Sometimes the actual structure of a chromosome may be made incorrectly, and a chromosome may be missing a part. It's unclear what causes the mutations to occur.
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Chromosomal disorders are the result of an error in the number or structure of the chromosomes. Some examples of chromosomal disorders in humans are:
- Down’s syndrome or trisomy 21: The individual has an extra chromosome 21.
- Trisomy 18 or Edwards syndrome: The individual has an extra chromosome 18.
- Trisomy 13 or Patau syndrome: The individual has an extra chromosome 13
- Turner’s syndrome: Girls with Turner syndrome have one X chromosome and are missing all or part of the other X chromosome
- Klinefelter syndrome: Boys with Klinefelter syndrome have two, or occasionally more, X chromosomes along with their Y chromosome.
- Cri-du-chat (cat cry) syndrome: The individual is missing the short arm on chromosome 5
- Prader-Willi syndrome: The individual has a deletion on chromosome 15.
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See All 2 AnswersChromosomal disorders can be diagnosed before birth using prenatal tests such as chorionic villus sampling (CVS) or amniocentesis or after birth using a blood test. Cells obtained from these tests are grown in the laboratory, and then the chromosomes are examined under a microscope. A picture of all the person’s chromosomes, arranged in order from largest to smallest is made. This picture is known as a karyotype. The karyotype shows the number, size and shape of the chromosomes and helps genetic experts identify any abnormalities.
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Chromosomal disorders are a result of an alteration in genetic material. These alterations can be grouped into three categories: error in number, deletions and point mutations.
Error in the number of chromosomes (too many or too few) includes the following disorders:
- Down’s syndrome or trisomy 21: The individual has an extra chromosome 21.
- Trisomy 18 or Edwards’s syndrome: The individual has an extra chromosome 18.
- Trisomy 13 or Patau syndrome: The individual has an extra chromosome 13
- Turner’s syndrome: Girls with Turner syndrome have one X chromosome and are missing all or part of the other X chromosome
- Klinefelter syndrome: Boys with Klinefelter syndrome have two, or occasionally more, X chromosomes along with their Y chromosome.
Deletion of a genetic material on a specific chromosome such as:
- Cri-du-chat (cat cry) syndrome: the individual is missing the short arm on chromosome 5
- Prader-Willi syndrome: The individual has a deletion on chromosome 15
Point mutation or any insertion/deletion entirely inside one gene examples include:
- Color blindness: Carried on the X chromosome and males with the gene have the disorder.
- Cystic fibrosis: Carried on chromosome 7 as a recessive trait.
- Tay–Sachs disease: Carried on chromosome 15.
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Klinefelter syndrome is typically caused by what is called nondisjunction, more specifically nondisjunction of the sex chromosomes. The X and Y chromosome are known as sex chromosomes, and their presence or absence determines the gender of the embryo. Normally, males inherit one X chromosome from their mother and one Y chromosome from their father. But those who have Klinefelter syndrome inherit an extra X chromosome.
The presence of an extra X chromosome is the result of a pair of sex chromosomes that fail to separate during the formation of the gamete (ova or sperm) in the parent. This failure to separate is referred to as nondisjunction. When the gamete with the extra chromosome unites with a normal gamate to form an embryo, that embryo may end up with three copies of the sex chromosomes (XXY) instead of the normal two (XY). The extra chromosome is then copied in every cell of the baby's body.
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See All 2 AnswersChromosomal abnormalities are caused by errors in the number or structure of chromosomes. Some examples of chromosomal abnormalities cause by an error in the number of chromosomes are:
- Down’s syndrome or trisomy 21: The individual has an extra chromosome 21.
- Trisomy 18 or Edwards’s syndrome: The individual has an extra chromosome 18.
- Trisomy 13 or Patau syndrome: The individual has an extra chromosome 13
- Turner’s syndrome: Girls with Turner syndrome have one X chromosome and are missing all or part of the other X chromosome
- Klinefelter syndrome: Boys with Klinefelter syndrome have two, or occasionally more, X chromosomes along with their Y chromosome.
Some examples of chromosomal abnormaliities cause by an error in the structure of the chromosomes are:
- Cri-du-chat (cat cry) syndrome: the individual is missing the short arm on chromosome 5
- Prader-Willi syndrome: The individual has a deletion on chromosome 15
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Riverside Center for Neurosciences answeredMost individuals with Angelman syndrome will have severe developmental delays, speech limitations, and motor difficulties. However, individuals with this syndrome can have normal life spans and not show developmental regression as they age. Early diagnosis and tailored interventions and therapies can help improve quality of life.
This answer is based on source information from the National Institute of Neurological Disorders and Stroke.