Introduction
Hemophilia is a type of inherited genetic disorder disease. It usually occurs in male births than female births. Patients who have hemophilia are lack of platelets to form a temporary plug if they are injured, their bodies cannot stop bleeding. There are three types of hemophilia which include hemophilia A, hemophilia B and hemophilia C. The previous two types of hemophilia are commonly seen than the last one.
Due to hemophilia is an inherited disease, there is a number of methods are available to diagnose hemophilia in the early pregnancy, if the mother is a carrier of hemophilia. Generally, using traditional diagnostic methods to detect hemophilia need taking a couple days to obtain the result. After many research and applications of the PCR technique in diagnosis of genetic disease, due to its accuracy and efficiency, it has become one of most commonly used technique in diagnosis of inherited genetic disease.
This essay will examine briefly what hemophilia is, then describe what is the main cause of hemophilia. Furthermore, giving more details about disease information.
In addition, it will explain how the PCR technique can be applied in hemophilia diagnosis and why it is superior to other diagnostic methods.
Background
Hemophilia is defined as a genetic disorder disease, which means in these patients’ bodies are lack of platelets that is used to form a temporary plug to prevent further bleeding. If individuals have hemophilia, when they got injuries or surgeries that may cause excess bleeding. Hemophilia even has three types; hemophilia A, hemophilia B and hemophilia C, but hemophilia A and B are the most common seen in hemophilia patients (Peyvandi et al., 2006). The former is due to the mutation of the blood coagulation factor VIII gene and around one of five thousand male individuals (Yarovoi et al., 2003). The latter affects the blood coagulation factor IX gene around one of twenty-five thousand to thirty thousand male births (Lin et al., 1997). All human beings have twenty-three pairs of chromosomes, Factor VIII and factor IX genes are located to Xq28 and Xq27 of the long arm of the X chromosome. Moreover, due to the flawed trait is carried on the X chromosome, it is called x-linked disorder. It means if the mother is a carrier who has hemophilia disease, she will transmit the defective x-linked gene her offspring, they have a half chance inherited hemophilia (Peyvandi et al., 2006). Hemophilia occurs in male births than female ones, due to male has only one X chromosome, so that the flawed gene is expressed in any male who carries it. In order to understand the potential risk of hemophilia, and deduce the prevalence of the hemophilia disease, to identify the mutation in the FVIII or FIX gene is important (Peyvandi et al., 2006).
Diagnosis
The PCR was invented by Kary Mullis in 1984, it was one of the remarkable inventions in the scientific field. It has influenced in many fields such as diagnostics and forensics in applied science. Moreover, the PCR technique can be used to detect the DNA or RNA of pathogenic organisms, also to be tested a wide range of diagnosis of infectious agents such as viruses and bacteria (Schaad and Frederick, 2002) .
The PCR tests have a number of advantages which are superior to traditional antibody-based diagnostic methods such as measuring the immune response to a pathogen. Moreover, they enable to detect the mutated gene in the inherited disease diagnosis, for instance, hemophilia.
Generally, there a number of different methods can be used to diagnose the genetic hemophilia disease. Firstly, family history analysis is also called linkage analysis. Linkage analysis relies on the family history to judge the incidence of inherited disease.Because of it has nearly 100 % accuracy, only a little chance around 1% risk of miscarriage needs for recombination (Tsui et al., 2011). But there is a limitation of using linkage analysis which is that only can be used to exclude the female carries status when a family with no previous hemophilia history (Peyvandi et al., 2006).
This information may not only help to examine the type of hemophilia but may also benefit to individuals who have a family history of hemophilia before they decide giving a birth.
Secondly, chorionic villi sampling (CVC) is the one of the most widely used methods to acquire fetal material for diagnostic purposes. It is used to check the fetal sex and then to examine limb abnormalities in gestational weeks 10-12. Generally, the sex result is being available within a day. Furthermore, In some case, in order to diagnose the fetal is affected with hemophilia or not, a further mutation diagnosis may take five to seven days (Ljung, 1999). Unfortunately, if the fetal is diagnosed to be with hemophilia, the advantage of CVS is helpful to determine terminating the pregnancy during the first trimester or not.
Even though the detection methods of inherited disease diagnosis have been developed rapidly, but there is still remains the difficulty to detect the mutation alleles which are inherited from a carrier mother (Tsui et al., 2011).
Since that, after numerous clinical tests, the PCR is proved that can be successfully applied in the detection of inherited diseases, such as hemophilia (Tsui et al., 2011).
The PCR allows to analyze DNA by using a single cell. It also can be used for genetic diagnosis by using single cells from embryos or genetic recombination analysis by using a single sperm or oocyte (Schaad and Frederick, 2002).
For the further the single gene flaw detection, it needs highly accurate and sensitive amplification plan, often using PCR or RT- PCR methods, because they are efficient enough and able to detecting as little as one or two target double-stranded DNA molecules in a single cell (Handyside et al., 2004).
The PCR takes an advantage of natural DNA replication mechanisms to produce a DNA sequence from a complicated mixture of heterogeneous sequences (Knowles et al., 2008).
The PCR can be used to amplify a specific region, the region can be very small bases or even a couple of thousand bases long which then being amplified to multiple times of duplications.
Using the PCR is to rely the different phases at different temperatures to incubate and amplify DNA sequences. The first phase is denaturation. That changes the target DNA from two stranded template to become a single stranded one. In the annealing phase, it is using lower temperature (lower than melting temperature three to five degrees ) to anneal specific primers and then they are bound to the single stranded template. The extension is the third phase, whereby the DNA polymerase (Tqp polymerase) to speed DNA synthesis at an intermediate temperature. Once the target DNA has been synthesized by the Taq polymerase to be a new stranded DNA template, the PCR cycles will be repeated twenty to forty times, until the target DNA sequence has been amplified (Knowles et al., 2008).
This technique has almost 100% accuracy in the diagnosis of families with hemophilia A or B . Hemophilia A and B are caused by the coagulation factor VIII (F8) and factor IX (F9) genes which are located on the X chromosome have become abnormal (Tsui et al., 2011).
Hemophilia A is caused by the coagulation FVIII gene mutation. It is interesting to note that there are near fifty percents of hemophilia A patients are caused by one or more inversions of the F8 gene. According to (Berg et al., 1990), they claimed that mutations which caused by hemophilia A are unique and discrete over the whole length of the F8 gene. The PCR can be used to detect the inversions by amplification of genomic DNA across the respective breakage sites. The specificity of PCR which includes classical or real-time PCR, it depends upon specific and designing PCR primers that are used to target the inversion of F8 gene (Schaad and Frederick, 2002).In various cases, the break points are found in the intron 22 of the F8 gene by PCR analysis (Habart, 2005). After that, using the Southern blot technique can examine these inversions, furthermore, that is possible to give more details of carriers and prenatal diagnosis to almost fifty percents of the families are with severe hemophilia A.
Recently, the PCR has been used widely because its cost and applicability (Peyvandi et al., 2006). However, it is too sensitive to miscarry so that samples should be strictly controlled to avoid the contamination with exotic DNA.
To sum up,
Available today for diagnosing a handful of disorders, including Cystic Fibrosis, in the future PCR technology may be used in predictive tests-methods for finding out who is predisposed to common disorders, such as heart disease and many cancers.
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