a genetic disorder

A genetic defect

A genetic defect is a disease caused by a flaw in one’s genetic material. This deformity may be caused by the insertion or subtraction of a whole chromosome, or by a single base mutation. It may be inherited from parents’ genes, but in certain diseases, the mutation may be caused by mutations in DNA; in this case, the disease may be inherited only if it occurs in the germline. Furthermore, certain genetic diseases can be inherited by mutations or variations in a preexisting gene or, in some cases, a set of genes. In this case, the difference could be due to changes in air exposure, or it could be random. Additionally, this disorder may be inherited from some different types of disorder which include, monogenic, multifactorial disease, chromosomal disorder.

Types of genetic Disorder

Single gene inheritance (monogenic inheritance)

It is a disease caused by variations in the DNA sequence of mono-cell. Monogenetic inheritance is more than six thousands unique genes, which occur in about one out of two hundred births. This disorder is easily traced through families, and the risk of it happening in a future generation can be anticipated because it is only a single gene that is involved. Further, the gene is divided into various categories: recessive, X-linked, and dominant diseases. In this case, recessive disorders only occur in the homozygous state where an individual carries alleles of the relevant gene and is affected when both parents transmit a single mutated allele and each pass on a transformed copy to the kid where the baby has received two altered copy. On the other hand, it is hard to trace recessive diseases because carriers of mutant allele show no symptoms (Veltman, Joris, and Han 565). However, the risk of having a recessive disorder increases when closely related individuals have a child together because the chances of having same mutant allele in both parents are higher.

Relatively, dominant diseases

are a single gene that occurs in the heterozygous state where mutant gene dominates the effect of the healthy gene, and as a result, mutant allele causes disease symptoms even though in the health allele is present. In every generation of an affected, the disorders tend to crop up because every creature that carries dominant mutant shows the symptoms of the illness. In cases where a person has two copies of the distorted gene, the disease symptoms are commonly severe. Moreover, X-linked conditions are a distinct inheritable syndrome that results from the existence of a metamorphosed DNA in the X chromosome (Veltman, Joris, and Han 565).

Women have two copies of X (XX) while men have a copy of X and Y (XY)

meaning that they only have a single copy of X chromosome which when mutated, there will be no real copy to restore healthy function. Interestingly, X linked disorder can either be recessive or dominant. Dominant X linked syndrome include Rett syndrome a disorder that is mostly found in girls. Surprisingly, a father cannot transmit this disease to their son, but it can be transferred to their daughter. Comparatively, X-linked recessive disorder comprises Duchenne, hemophilia, muscular dystrophy and red-green color blindness which is much more common in males than in females.

Relatively, X-linked recessive situations comprise red-green color blindness

meaning that an individual cannot distinguish between red and green color, but his ability to see is healthy. In this case, females are less affected than males since the gene is placed on X chromosome. Additionally, to determine the inheritance of red-green colorblindness, the genotype of parents must be considered. For instance, if a mother is a carrier of color blindness XaXb and a father has XaY normal vision, then their son has a fifty percent of color blindness because he inherits X chromosome from mother and Y chromosome from the father.

Multifactorial Disorder

Multifactorial Disorder is a disease caused by a combination of genes and environmental and nutritional factors. Multifactorial inheritance is multiple genes that determine a phenotype being at different loci and its effects are cumulative where each gene contributes a small amount to a final phenotype that is aided by certain environmental factors. Moreover, the genes are neither dominant, nor recessive to another. An example of such diseases is congenital heart defects, diabetes, and cancer. However, the genetic disorder is rarely treatable, and in some cases, gene therapy, bone marrow transplants, enzyme replacement is tasted to treat them. In some diseases such as cancer, the cell grows abnormally making it difficult for the cell to divide to carry out their functions as well as replacing the damaged tissues.

Multifactorial disorders are complex in their origin

because of coming together of some influences and at times including external variables and multiple gene runs in families. Therefore, individual’s family health history may indicate that set of genesis in a family where there is a greater risk of evolving the disorder among 1st, 2nd and 3rd-degree family member of the affected individual.

Chromosomal Disorder

This disease results from a change in number or chromosome structure. It happens when the whole chromosome is duplicated, altered or missing. Some chromosome abnormalities are associated with clinical disorder while others are harmless (Battaglia 592). On the contrary, the most severe chromosome disorders are caused by the gain or loss of the whole chromosome which in some cases it can affect thousands of genes. In case of structural abnormalities, chromosome disorder occurs when large sections of DNA are missing. Additionally, structural defects can proceed in several forms, which include: deletion, duplication, and translocation.

Deletion

is a mutation that causes part of the chromosome o be missing. Duplication is a mutation that causes some part of the chromosome to be copied and therefore resulting in the additional genetic material. Translocation is a mutation that causes one portion of a chromosome to be relocated to a different part of a chromosome or a different gene altogether. In this case, it can reciprocate where segment from two different chromosomes are exchanged. On the other hand, the whole chromosome can attach itself to another chromosome in a process known as Robertsonian.

Chromosomal Changes leading to Down Syndrome

Genetic material is stored in nucleus found in every cell of a human being (Muchová, Zitnanova, and Z. Durackova 535). The genetic material in genes carries the code accountable for all genetic features that are assembled along rod-like structures called chromosomes. Naturally, each cell nucleus comprises twenty-three pairs of chromosome half of which are originated from parents. Therefore, Down syndrome takes place when an individual has a full or incomplete extra copy of chromosome 21. The added genetic material varies the course of growth and leads to the distinctive related to Down syndrome. Some of these individualities include small stature and a low musical tone. In the majority of cases, DS is not inherited, and it occurs because of a chance that happens during conception.

Types of Down syndrome

Trisomy 21

An error in cell division called nondisjunction cause Down syndrome, and it results from an embryo that has three copies of chromosome 21 instead of the usual two (Roizen 875). In the course of the formation of egg or sperm, an error may occur in meiosis process causing the egg or sperm to receive an extra copy of chromosome 21.as an embryo grows, the additional chromosome is replicated in every body cell. As a result, trisomy 21 is a Down syndrome, which is ninety-five percent cases.

Mosaicism

In mosaic Down syndrome, not all cells are likely to have an extra chromosome because not all human cell is the same. Persons with Mosaic syndrome may have less physical appearance compared to those with another syndrome. However, vast generalizations are not likely because of a broad range of capabilities with Down syndrome possess (Roizen 875). On the other hand, Mosaicism accounts for only one percent of all form of Down syndrome cases and is the least common form.

Translocation

It accounts for about four percent of Down syndrome, and the total number of chromosome remains 46. Moreover, during the division of cells, some parts of chromosomes can break off and attach itself on another chromosome and can be transferred to other cells an error that accounts for four percent of Down syndrome (Roizen 875).

Causes of Down Syndrome

All individuals with Down syndrome have an additional part of chromosome 21 irrespective of the nature of Down syndrome that changes the course of expansion and causes the characteristic related to Down syndrome. It is caused by the existence of an extra chromosome in babies’ cell. However, according to scientific research, there is no proof, which, shows that Down syndrome is caused by environmentally friendly factors or maternities events before or through gestation. On the other hand, an entire extra copy of a 21st chromosome that leads to Down syndrome may come from father or mother (Englund 648).

Risk Factors

Maternal age

The age of a mother at the conception of a fetus with Down syndrome is a significant risk factor of meiotic nondisjunction of chromosome 21. Women passed the age of twenty-five has a greater danger of conceiving a kid with Down syndrome since old ovaries lack the ability of proper chromosomal division. On the other hand, women below the age of 35 can also give birth to a child with DS, and this can be featured by giving birth to many children.

A child conceived with Down syndrome

A baby born with Down syndrome has the same sequences of hormonal and physical changes related to puberty just like other kids (Coppedè 2920). Nevertheless, there is a delay in growth of strong self-control, simple communication, social maturity and mental thinking.

Symptoms of Down syndrome

At birth, a baby with Down syndrome includes the short neck, bulging tongue, eyes that slant upward, flat facial features, small ears and poor muscle tone. The Down syndrome is accompanied by medical complication such as obesity, Alzheimer’s in later life, sleep apnea and poor vision. Additionally, individuals with DS are further likely to conduct infections such as respiratory disease, urinary tract infection and, skin infection (Coppedè 2920).

Works Cited

Battaglia, Agatino, et al. “Confirmation of chromosomal microarray as a first-tier clinical diagnostic test for individuals with developmental delay, intellectual disability, autism spectrum disorders and dysmorphic features.” European journal of pediatric neurology 17.6 (2013): 589-599.

Coppedè, Fabio. ”Risk factors for Down syndrome.” Archives of Toxicology 90.12 (2016): 2917-2929.

Englund, Annika, et al. ”Changes in mortality and causes of death in the Swedish Down syndrome population.” American Journal of Medical Genetics Part A 161.4 (2013): 642-649.

Muchová, J., I. Zitnanova, and Z. Durackova. ”Oxidative stress and Down syndrome. Do antioxidants play a role in therapy?.” Physiological research 63.5 (2014): 535.

Roizen, Nancy J., et al. ”A community cross-sectional survey of medical problems in 440 children with Down syndrome in New York State.” The Journal of Pediatrics 164.4 (2014): 871-875.

Veltman, Joris A., and Han G. Brunner. ”De novo mutations in human genetic disease.” Nature reviews. Genetics 13.8 (2012): 565.