Fragile X Syndrome Inherited

12. Explain why more males tend to suffer from X-linked disorders than females. (5 points) Males tend to suffer from X-linked disorder more often than females because females have more X chromosomes than males.

The mother, who is a carrier, inherits an X-Linked or sex-linked faulty gene. The result is producing an affected son and or a daughter being a carrier. The second way is an affected male producing children, particularly daughters. All daughters born to fathers with x-linked muscular dystrophy will be carriers; on the contrary their sons will be unaffected. Scientists link this to a genetic mutation in the gene, appearing most often for the first time in a family.

Turner syndrome results in a monosomie of chromosome X and is the only viable monosomie known. One in every 5,000 newborns can inherit this disease. The mental abilities are not affected, although they are usually sterile owing to underdeveloped sex

Females are carriers in their X-Chromosome and they have the chance of passing the disease on to their children, 50-50 to a girl and 50-50 to a boy. If the girl does receive the gene she becomes a carrier. If the boy gets the gene then he has the disease. Males do not pass on the gene to their children because they pass on the Y-chromosome and the disease is X specific. Some female carriers have indicators of being a carrier by having symptoms of cardiomyopathy, shortness of breath during exercise, and muscle weakness in the back, arms, and legs. There have been very rare instances where a girl has not received a

This syndrome is from a mutation of a gene on chromosome 15 and this causes problems in the production of fibrillin-1 which is a protein that is an important part of connective tissue. The name for the gene is FBN1. Basically, it is the “glue” that helps to support the tissues in the human body. A child born to a parent with this syndrome has a 50% of having it. However, in the remaining 25%, neither parent has the disease which gives them a 1 in 10,000 chance of having a child with this disorder. When a child of two unaffected parents is born with it then the genetic mutation occurs in either the egg or sperm cell at the time of conception.

Approximately one-third of the females with Fragile X Syndrome have a substantial learning disability, the other two-thirds have mild to moderate intellectual disabilities. This two-thirds may also experience issues related to their mental/emotional health as well as social and/or general anxiety disorders. Although rare, there are some females whose FMR1 Gene, which is the gene responsible for causing FXS, fully mutates; thus, eliminating any apparent signs of Fragile X Syndrome. These females usually remain undiagnosed until another family member is diagnosed with the syndrome.

Fragile X Syndrome is a genetic condition causing intellectual disability, behavioural and learning challenges and various physical characteristics, it occurs in both genders but effects males more. Also is the most common gene for Autism worldwide, every week in Australia one child is born who is fully affected and 20 children are born who are carriers. It is estimated that 5 per cent of people with a diagnosis of an Autism Spectrum disorder also have Fragile X.

Normally males have 46 chromosomes which include one X and one Y chromosomes, but males with XYY Syndrome have 47 chromosomes, two of which are Y chromosomes. Most cases of XYY Syndrome occur before conception due to a cell division error in the sperm. Rarely does the cell division error happen after conception.

Five other gene disorder that contributes to autism are (1) "EN2 (Engrailed 2) involved in cerebellum development. (2) GABR (Gamma Amino Butyric Acid Receptor) regulates brain cell migration. (3) OXTR (Oxytocin Receptor) participating in the response to stress and social skills. (4) RELN (Reelin) involved in neuronal migration in the developing brain. (5) SLC6A4, a serotonin transporter gene” (Johnson, Giarelli, Lewis, & Rice, 2013). As a result of all the researches done several chromosomal loci have been shown to be linked to Autistic Spectrum disorder including those at 2q24-2q31, 7q22-7q31, 7q34-7q36, and 17q11-17q21. Structural chromosomal changes involving deletions and duplication at 7q11, 15q11-15q13, 17p11.2, 22q11.2, and 22q13 have also been associated with forms of autism. However, the most common chromosomal abnormalities currently associated with autism include the fragile X mutation, other sex chromosome abnormalities, and abnormalities of 15q11-q13. “Evidence has shown that duplications of 15q11–q13 have led to higher risks of Autism Spectrum Disorder and developmental and cognitive deficits” (Flashner, Russo, Boileau, Leong, & Gallicano, 2013). Chromosome 15q11-q13.1 region is subject to genomic imprinting, which is an epigenetic process that results in monoallelic gene expression. Duplications lead to autism and are usually maternal in origin. Deletion of the maternal allele of chromosome 15q11-q13 cause Angelman syndrome (AS) a neurodevelopmental disorder

Fundamentally, mutations of the FMR1 gene occur in which a DNA segment, specifically the CGG triple repeat, which contains instructions for producing a protein called FMRP, is excessively expanded within the gene. Normally the segment is repeated five to forty times in the gene, but in Fragile X Syndrome the strand is repeated over 200 times. The abnormally expanded segment mutes the FMR1 gene, preventing it from producing the protein, FMRP. Deficiency of the protein disrupts functions of the nervous system resulting in the symptoms of Fragile X Syndrome. The condition is inherited through an X-linked dominant pattern.

Fragile X Syndrome was identified in the year 1991. This disability affects more males than females. Approximately 1 in 4,000 males are affected, however only 1 in 8,000 females are affected (Lombroso, 2003). Fragile X generates in the FMR1 gene. Fragile X is caused by an excessively repeating tri-nucleotide,

Genes are often named after their condition. The gene is called FMR1 gene; this acronym stands for Fragile X Mental Retardation gene. It is typical of the FMR1 gene to repeat seven to sixty times the CGG pattern. This is normally repeated approximately 30 times; however, in this instance it repeats well above the average. An individual with the syndrome may have well over 200 repeats of the gene. With such high numbers of the gene created the methyl group bind together with the C bases (or cytosine) affecting the gene and causing it to be deactivated. This gene is present in everyone and is responsible for the development of the brain and testes by producing a protein that allows other genes to work normally (Saunders, S., 1999). Due to the gene not functioning, it does not create the protein needed for brain development. This is how Fragile X Syndrome

Fragile X Syndrome, also known as FRAXA syndrome, fra(X) syndrome, FXS, marker X syndrome, or Martin Bell syndrome, is a disorder onset by a genetic mutation in the FMR1 gene. This gene produces a protein called FMRP which regulates the production of other proteins and plays a role in the development of synapses, which are specialized connections between nerve cells (National Library of Medicine, 2014). The FMR1 gene has a DNA segment called CGG triple repeat, which is repeated about 5 to 40 times in a typically developing individual. There are two type of mutations associated with Fragile X: A full gene mutation and a gene premutation. In cases of individuals with a full gene mutation, the CGG segment is repeated more than 200 times (National Library of Medicine, 2014).

Genetic disorder has many diagnostic and common names for example, DMD is also known as Duchenne muscular dystrophy or Becker and pseudohypertrophic muscular dystrophy. DMD is a genetic disease that occurs mostly in boys. According to the “Muscular Dystrophy Association DMD is inherited in an X-linked pattern, because the gene that can carry a DMD-causing mutation is on the X chromosome. The male host inherits an X chromosome from his mother and a Y chromosome from his father, which is what makes him male. The female host inherits two X chromosomes, one from each parent.” (MDM). “The human X chromosome carries regions prone to genomic instability: deletions in the Xp22.31 region, involving the steroid sulfatase gene cause X-linked ichthyosis; rearrangements in the Xp21.2 region are associated with Duchenne or Becker muscular dystrophies (DMD or BMD); and the Xq27.3 unstable region, containing the (CGG) in repeat expansion in the FMR1 gene is associated with fragile X syndrome stated in the article, “A Family with Fragile X Syndrome, Duchenne Muscular Dystrophy and Ichthyosis Transmitted By An Asymptomatic Carrier”(Todorova, A)

The XXY syndrome, most commonly known as Klinefelter syndrome (KS), only affects males of all ages. This syndrome occurs when there is a random genetic error after conception and is not curable, however treatment can help.All females have XX chromosome and all males have XY chromosomes. Unlike the normal XY type that all males have, males affected have an additional X chromosome which results into many symptoms such as impaired spermatogenesis, low testosterone, and male hypogonadism. Since Klinefelter syndrome is related to the sex chromosomes of males, it is a sex link trait.