Hereditary Chromosome Disorders
Hereditary Chromosome Disorders
The discovery of 44 chromosomes in the human body; was discovered in 1956. This information established clinical cytogenetic era which has rapidly developed due to scientific, technological innovations. Over the next few decades, significant discoveries were also reported about altered chromosomes that led to numerous primary chromosomal disorders such as Turner syndrome (45, x), down syndrome (trisomy21) and Klinefelter syndrome (47, XXY). Significantly, the genetic disease has since been caused by hereditary chromosome disorders. The affected individuals suffer from various abnormalities such as stillbirths, malignancy pathogenesis, infertility, retardation as well as reproductive loss. According to multiple studies, these hereditary chromosomal disorders contribute to over half of the spontaneous abortions, 0.5% of babies born with the disease, over 5% of miscarriages as well as 7% of all stillbirths. Over 2% of all pregnant women above the age of 35 also experience chromosomal abnormalities and disorders (Mutesa et al., 2010). Studies reveal that there are numerous different types of chromosome disorders which are grouped into two: structural and numerical. Anatomic disorders refer to abnormalities of the chromosome with extra, missing and switched up parts. Mathematical complications occur when the typical pair of the chromosome has missing or extra chromosomes. In the early development stages of the fetus, these hereditary chromosome disorders arise. At times, genetic errors are triggered by particular environmental factors as well as the mother’s age. Chromosome disorders can be detected using specific approaches such as the use of prenatal tests and screens. The different effects caused by these disorders result from the difference brought about by the chromosome structure and numbers.
Occasionally chromosome segments re-join incorrectly or may break leading to structural abnormalities that cause the chromosome disorder. Therefore, chromosome disorder results from a variety of structural chromosome abnormalities. Structural rearrangements of chromosomes can either be balanced or unbalanced. Unbalanced rearrangements occur when chromosome segments get deleted, inserted or duplicated. Another form of structural chromosome abnormality is when a chromosome breaks into two with the broken ends forming a circular chromosome known as the ring chromosome. Therefore, this study discusses hereditary chromosome disorders as well as their resulting consequences.
Chromosome disorder simply refers to a condition where the chromosome structure or number is altered. Chromosomal changes result in interference with the cell genetic information. As a result, an individual may experience problems related to body system functioning, development, and growth. Chromosomal abnormalities take place when the egg or the sperm is produced or during the early development stage of the fetus. These chromosomal abnormalities are hereditary and can be passed from parent to child. Therefore, these chromosome abnormalities that can be moved from one generation to another are referred to as inherited chromosome disorders (Crandall, 1977). Thus, this paper analyzes these hereditary chromosome disorders to enhance the reader’s understanding while making contributions to previous studies.
Survival of the foetus with chromosome disorders is rare. According to various studies, cytogenetic mistakes from parents result in over half of abortions in the first 12 weeks of pregnancy. These studies also reveal that in every 200 new born’s at least one newborn is observed to suffer from hereditary chromosome disorder. These disorders can be tested through various test mechanisms such as karyotyping, fluorescence in situ hybridization and microarray. For instance, in karyotype tests, amniotic fluids or blood samples are taken by cytogeneticists whose role involves staining these chromosomes before correctly arranging them with emphasis placed on length. As such, investigators can identify any pattern changes. Numerical abnormalities are commonly tested using the Giemsa stain method also known as the S-banding. On the other hand, numeral abnormalities are easily identified. Hereditary chromosome disorders can also be classified into two categories: sex and autosomes chromosomes.
Chromosome disorder ethology
The chromosome disorder ethology varies from one person to another. During cell division, abnormalities primarily result from mistakes. This occurs when the ovum or sperms develop poorly. Cell division takes place in two different ways: meiosis and mitosis. Such errors during cell division may be caused by other factors such as environmental influence and maternal age. Chromosome disorders are considered to be fatal. Hereditary chromosome disorders have severe side effects on children that survive as they are subjected to severe problems associated with their physical and mental well-being. It is essential to screen for these hereditary disorders to ensure that measures are effectively taken to ensure that chances of inheritance are reduced. This is possible through the use of karyotype testing.
(a)Cell division problems
Cell division takes place through two different processes: meiosis and mitosis. Meiosis involves a process through which reproductive cells undergo division. As a result, 23 chromosomes are born in a cell which is known as a haploid. The mother and father both contribute 23 chromosomes each to the fetus. As such, the cells are considered to be in a state of diploid (2n) in the fetus. As such, during meiosis mistakes inherited from the parents alters the chromosome numbers either in the sperm or egg. Hence, the child inherits a more or less number of chromosomes. Genetic information is duplicated during the process before materials are halved. One parent cell is made up of 92 chromosomes (4n). The typical cell is split into two subsidiary cells each consisting of 46 chromosomes (2n). After fertilization, mitosis begins and continues through a person’s life. Several chromosomes in the cells are altered when a mistake takes place. A mosaicism problem occurs due to mitosis.
(b)Age of parents
Maternal age plays a crucial role in chromosome disorder inheritance. Even though, the effect of paternal age is minimal, it must still be considered by physicians during their analysis. The process of female cell division stops at birth. During the meiosis process, the cells undergo several divisions. Inheritance of chromosome disorders is enhanced especially with parents that give birth in their later years. Sperm cell development takes about 72 hours. During this period, there is a less likelihood that a mistake occurs which triggers chromosomal disorder inheritance (Blachford, 2001). It is advisable for older women to visit centres of genetic counselling. These include all women above the age of 35 years. The prenatal diagnosis determines parents who possess chromosomal disorders.
The environment is a critical factor that determines whether children from their parents inherit chromosome disorders. However, recent studies find it difficult to differentiate significantly between parents with healthy children and their counterparts having children with chromosome disorders. This is mainly because both these parents live in the same environment space with similar habits and lifestyles (Blachford, 2001). However, other factors in the surrounding such as medication, x-rays, and food have proven to be very impactful on chromosome disorder inheritance. Studies show that these factors have a cumulative effect.
Pinpointing the primary cause of chromosome disorder inheritance is difficult. As such, medical practitioners are increasingly facing challenges associated with making appropriate prevention recommendations. Other studies have previously stated that effective prevention of chromosome disorder inheritance is achievable through the incorporation of the folic acid. Risks for pregnant women can also be reduced by ensuring that they obtain enough vitamins.
Structural abnormality types
The translocation process involves the transfer of one chromosome part to another chromosome. Emphasis must be placed on the balance or unbalanced nature of the translocation process. A balanced translocation is characterized by the equal exchange of parts between two chromosomes; hence no genetic material is lost as the number of chromosomes remains the same: 46 chromosomes.
Typically, the breaking point of the chromosome is close to the centromere. A loss of acrocentric chromosomes characterizes the process. During fertilization, problems may occur even when the translocation is balanced due to complications of gamete carrier inherited from the parent cells. As such, unbalanced zygotes are produced due to the interruption of the pairing process of the homologous chromosomes (Crandall, 1977). As a result, the offspring abnormalities are caused by the state of unbalanced gametes. This is due to a shortage of essential genes prompted by chromosome alteration as the offspring receive it. Hence, reproductive failure is detected as the clinical symptom that corrupts the balance of the translocations.
Klinefelter syndrome (XXY)
This disorder occurs in males due to an extra X chromosome. In every 500 living males, one male is affected by the disease. In most cases, the extra chromosome in males is inherited from the mother. Patients diagnosed with the disorder have average to below the average level of intelligence. Patients also face difficulties in planning as well as reading disabilities. A common denominator among such individuals is poor language skills (Crandall, 1977). Such children face recurring issues due to their inability to learn from past mistakes, poor judgment as well as lack of insight. Affected people have varying physical appearances even though most of them are characterized with long legs and arms. In most occasions, such people are observed to have regular appearances also though they have slightly wider hips than ordinary people.
Such individuals are characterized by small testes even though they seem to have normal puberty timing. During puberty, such males experience increased breast size than usual scares facial hair growth. Usually, these males are characterized with infertility even though in some instances sperms can be produced for individuals with developed testes. Males diagnosed with Klinefelter syndrome are often predisposed to certain illnesses such as breast cancer, diabetes mellitus, hypothyroidism, and chronic lung disease when compared to other men (Puiu, Emandi & Arghirescu, 2013). Other affected males are known to possess even up to 5 X chromosomes. Physical abnormalities and intellectual disability are severely affected as the number of chromosomes increases.
Cytogenetic testing is conducted during a prenatal diagnosis. However, it is detected during a clinical appearance during which tests are done using a chromosomal microarray analysis or using the karyotype test. During a physical examination, an adolescent may be suspected to be diagnosed with Klinefelter syndrome in case such individuals exude small gynecomastia and testes. As such most of these men are diagnosed with a state of infertility.
An endocrinologist is mandated with the duty of evaluating males diagnosed with Klinefelter syndrome. The endocrinologist establishes the testosterone supplementation indication before recommending a testosterone therapy. Male sexual characteristics such as the structure of the bone, muscle bulk and improved function of the body physique are developed by starting the testosterone therapy during puberty (Blachford, 2001). Males with Klinefelter syndrome have a higher chance of developing behavioral problems when hormone therapy is conducted at an early stage according to several studies. Development cognitive abilities as well as reading and language comprehension skills neuropsychological tests and speech therapy could also prove to be beneficial to these males diagnosed with Klinefelter syndrome. It is also important to counsel these boys once puberty commences creating awareness on the likely changes as well as what is expected of them during these transitional periods.
Fragile X chromosome
The fragile X chromosome is a type of chromosome disorder that is inherited by males. The disease primarily causes intellectual disability. The primary cause of the disorder is an abnormality occurring on the X chromosome of a particular gene. In every 4000 males, one male is affected by the fragile X syndrome whereas, for every 8000 females, one female is affected. Such individuals commonly inherit the disorder due to permutation. Typically, the disorder impairs males more than females. The disease does not necessarily cause clinical symptoms because it is acquired as an X-linked pattern.
According to previous karyotype examinations, the chromosomal abnormality of the syndrome was primarily because of its genetic material structure with a thin strand as the X chromosome had constricted long arm ends (Mutesa et al., 2010). According to modern cytogenetic mechanisms that are being deployed the Fragile X chromosome currently is no longer considered a chromosomal anomaly and is now referred to as a single-gene disorder due to a lack of structural defect from its appearance.
Individuals diagnosed with Fragile X syndrome depict abnormalities related to cognitive, physical as well as behavioral abilities. Such individuals are characterized by symptoms such as large foreheads and chins, prominent protuberant ears, macroorchidism as well as increased arched palate.The disorder is associated with mild to average intellectual disability as such individuals exude features such as poor eye contact, instances of autism and social anxiety.
People can determine the disorder diagnosis by undergoing DNA tests. However, diagnosing the disorder has become increasingly difficult because its symptoms become clear when one reaches middle school. Intellectual disability and autism are indicators of Fragile X syndrome; hence individuals with such qualities must be tested for the disorder. It is also essential to carry out tests on people whose maternal relatives are affected.
Individuals diagnosed with Fragile X syndrome require support measures to be taken during the procedure due to their state of feeling isolated and abandoned. Maximizing the abilities of children diagnosed with Fragile X syndrome, such initiatives such as occupational therapy and language therapy can be initiated at an early stage. Children could also benefit from other medications such as antidepressants and stimulants.
This paper focuses on evaluating hereditary chromosome disorders. There are numerous chromosome disorders such as Down’s syndrome, Turner syndrome, Klinefelter syndrome, trisomy 13, trisomy 18, Fragile X syndrome, XYY syndrome, and XXX syndrome. However, there are a few chromosome disorders that are inherited from parents by children. Hereditary chromosome disorders include Klinefelter syndrome and Fragile X syndrome. Therefore, this study attempts to elaborate some of the causal factors that impact chromosomal abnormalities and disorders such are the age of parents and environmental factors. While studying the hereditary chromosome disorders, the study elaborates on their symptoms, diagnosis and treatment processes. The study seeks to make contributions to previous research papers to increase people’s knowledge of genetic disorders.
Blachford, S. (2001). The Gale encyclopedia of genetic disorders.
Crandall, B. F. (1977). Genetic disorders and mental retardation. Journal of the American Academy of Child Psychiatry, 16(1), 88-108.
Mutesa, L., Uwineza, A., Hellin, A. C., Mambo Muvunyi, C., Vanbellinghen, J. F., Umurerwa, L., … & Nyundo, M. (2010). A survey of genetic diseases in Rwanda. Rwanda Medical Journal, 68(3), 5-17.
Puiu, M., Emandi, A. C., & Arghirescu, S. (2013). Genetics and obesity. In Genetic Disorders. IntechOpen.
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