The importance of Genetics in medicine

Introduction to medical genetics

In medicine, there is a branch that deals with diagnosing and treating disorders caused by hereditary factors. It is not the same as human genetics. The latter is a branch of scientific enquiry that deals with research in human genetics in general. It may be applied to medicine or not, but when it is applied, it is medical genetics. A study under human genetics may deal with the analysis of genetic disorders. But medical genetics on the same topic would include diagnosing, treating, and counselling people with these disorders. The information we get from studies on human genetics may not have any relevance in medicine. Medical genetics is also referred to by the term 'genetic medicine. This term includes ways of managing symptoms of genetic disorders such as personalised medicine, gene therapy, and predictive medicine. 

Application of genetics in medicine

The field of medical genetics covers a variety of areas. It includes physicians, nutritionists, and genetic counsellors who own clinics. It also includes the laboratories that these clinics use for diagnosis and research that look into the factors that cause genetic disorders. Some conditions that fall under the field of medical genetics are

• Dysmorphology
• Birth defects
• Intellectual disabilities
• Mitochondrial disorders
• Autism
• Disorders with connective tissues
• Skeletal dysplasia
• Prenatal diagnostics
• Cancer genetics

The above list is an example of the application of genetics in medicine. The field of medical genetics has many applications in the management and treatment of common diseases. In addition, it overlaps with other fields of medicine, and these overlaps are becoming more recognised. Likewise, with the advances in the study of genetics and technology, we have started to see the possible genetic factors that may affect medical conditions. Moreover, these conditions concern endocrine, morphologic, pulmonary, cardiovascular, renal, ophthalmology, dermatology, and psychiatry. Genomic and elective genetic testing has become more common in recent years, and the medical genetics community is interested in involving themselves. 

Genetics in medicine and its specialists

There are several subspecialties within the field of medical genetics. They are often combinations between research and clinical care. This is partly due to technological advances that enable us to understand hereditary and genetic disorders in depth, which was not possible before. 

Clinical genetics

Clinical genetics is an application of genetics in medicine. This form of clinical medicine focuses on hereditary disorders. Patients referred to this field may have various reasons like birth defects, autism, developmental delay, short stature, etc. Patients who come to such clinics and undergo treatments could suffer from Down syndrome, chromosomal rearrangements, DiGeorge syndrome, Marfan syndrome, Fragile X syndrome, Turner syndrome, Neurofibromatosis, and Williams syndrome. 

Biochemical/ Metabolic genetics

Biochemical genetics is another application of genetics in medicine. This includes the diagnosis of errors in metabolism that are inborn, as well as managing symptoms caused by these errors. Patients often suffer from deficiencies of enzymes that disturb the biochemical processes responsible for the metabolism of amino acids, carbohydrates, and lipids. Some of the various metabolic disorders are: 

• storage disorders of glycogen or lysosomes 
• galactosemia
• metabolic acidosis
• urea cycle disorders
• peroxisomal disorders
• Phenylketonuria.  

Cytogenetics: 

Another application of genetics in medicine is an analysis of chromosomes and their abnormalities. Analysis of chromosomes was based on microscopy before. But with the invention of new technologies based on molecular structures, there are more accurate ways of analysing cytogenetics now. Some chromosomal abnormalities are rearrangements, duplicate disorders or genomic deletions, and aneuploidy.

Molecular genetics

Molecular genetics is an example of the application of genetics in medicine. This is the discovery and analysis of DNA mutations through laboratory testing where the disorder involves a single gene. Some such disorders include cystic fibrosis, achondroplasia, hereditary mammary cancer, Duchenne muscular dystrophy, Marfan syndrome, Huntington's disease, Rett syndrome, and Noonan syndrome. One may also apply it in diagnosing epigenetic disorders like Prader-Willi syndrome, Beckwith-Wiedemann syndrome, Angelman syndrome, and disomy from one parent. 

Mitochondrial genetics

Mitochondrial genetics is another example of genetics in medicine. This includes the management and diagnosis of disorders concerning the mitochondria of the cells. The basis for these disorders may be molecular but can result in biochemical disorders because of inadequate energy synthesis. 

Genetic disorders have severe effects that are present not just in one person but may be present in many family members since it has connections to genes. Genetic counselling provides:

• Patients and their family members with information about the concerning condition.
• Tests are mandatory for diagnosis.
• The risks that other family members may be in.

The counsellors themselves are the members of the team who are not the physician but are experts in assessing family risks and providing counselling for the patients. The condition, as well as the age of the patient, are the parameters involved in determining their exact role. 

History of genetic medicine 

Genetic studies started way back in the 19th century, but human genetics evolved as a special field in the 20th century. The field of medical genetics emerged as a result of the fall of eugenics. The latter, having been misused in the second World War, was rapidly losing popularity. The need for a scientific approach to studying genetics to diagnose and treat genetic disorders led to the field we now know as medical genetics. 

There may be various kinds of clinics which deal with different genetic disorders. With the right equipment and setting, a clinic may also have the capacity to diagnose and treat patients with an array of genetic conditions. There are genetics clinics for outpatients that evaluate diagnoses. These may be present in hospitals as well. Some genetics clinics specialise in specific kinds of disorders. There are also special clinics that counsel pregnant women and can conduct various tests on them for diagnoses that would concern the unborn baby. There are also multidisciplinary clinics that offer treatment and counselling for all sorts of genetic disorders. 

Finding genetic disorders

Every patient ready for a test will undergo a diagnostic evaluation to suit their specific symptoms. The geneticist may present various possible diagnoses, and the patient will undergo different tests to determine the actual condition. Some ways of determining genetic disorders are:

Chromosome studies 

This is mostly concerned with determining the factors that lead to delay in the development of mental faculty, dysmorphic features, birth defects, or autism. One may do it prenatally to determine if a foetus has any chromosomal disorders. These abnormalities may be found in cancer patients as well. A few methods used in chromosome analysis are:

Karyotype uses special stains to generate dark and light bands that we can use for identifying every chromosome using a microscope.

FISH (Fluorescence In-Situ Hybridization) is the use of fluorescent labelling by which they analyse the binding of DNA sequences which can locate changes in the positioning of chromosomes. 

Fluorescent probes are important in chromosome painting, where each chromosome is labelled differently.

There is a new molecular technology known as Array Comparative Genomic Hybridization. In this process, we hybridise a single DNA sample into a microarray chip or glass slide that contains molecular probes. Each represents a unique region of the genome. 

Basic Metabolic Studies

 Metabolic imbalances found in bodily fluids are visible through biochemical analysis. In addition, a specific test is also there for a particular enzyme function. So, if a patient has a probability of having a metabolic disorder, one may put him or her through one of the following tests:

One can analyse amino acids quantitatively using the ninhydrin reaction. After this, they will perform liquid chromatography, which will tell how much amino acid is present in the sample taken from the patient. 

Both qualitative and quantitative analysis is effective in urine organic acid analysis, which detects abnormal organic acids by examining the patient's excreta. 

Compounds like fatty and organic acids can be detected using acylcarnitine combination profiling. 

Detection of excess lactate and pyruvate in patients may mean a metabolic disorder. 

If the amount of amino acid level is high, it may mean that the patient has some disorder regarding the urea cycle or liver. 

Molecular Studies

 DNA sequencing directly analyses a genome's DNA sequence. This kind of analysis is very specific but covers only a particular gene at a time and may not reveal all possible genetic mutations. Another type of molecular study is DNA methylation analysis. A previously popular technique is Southern blotting, where we detect abnormalities in DNA fragments using gel analysis and radiolabelled probes.

The DNA present in each of our cells has a coating of chromosomes. Genetic disorders are usually the outcome of genes or chromosomes that have gone through alterations. There are no cures that can correct these mutations. But many genetic disorders can be treated by managing the symptoms. Likewise, extensive research has resulted in detailed information about the manifestation of the disorder. So, one can use this information to make dietary or medical management plans that are useful in reducing any possible severe complications. The most recent studies are focused on gene therapy. 

There are a few ways to manage metabolic disorders: 

Diet

 Restricting diet and taking supplements are often advised to patients to treat several metabolic disorders. So, restrictive diets may be hard to maintain for the patient and their family. So, one must consult a nutritionist regularly as the specifics of the diet can change according to the patient's needs. 

Medication

 By using medications, one may enhance the activity of a residual enzyme, there may be an inhibition of the enzymes that block biochemical pathways, or some toxic compound can result. 

Enzyme replacement therapy

 Some diseases concerning lysosomal storage are treatable by infusing laboratory-produced recombinant enzymes. This reduces the build-up of compounds. However, this treatment has several limitations and may cause allergic reactions. 

If you are considering starting a career in medical genetics, there are wide varieties to choose from. All these options will involve getting the proper training to qualify for the position. In addition, you can become a part of a medical genetics team as: 

• Clinical geneticist, 
• Genetic counsellor, 
• Metabolic nurse, 
• Nutritionist, 
• Biochemical diagnostician, 
• Cytogenetic diagnostician, 
• Molecular geneticist, 
• Research geneticist, 
• Laboratory technician.

Research in medical genetics is wide-ranging. So, it includes basic research concerning the human genome and genetic inheritance, mechanisms of metabolic and genetic disorders, and newly invented treatments and the impact of these treatments. 

The connection between a medical condition and a rare gene may be subtle and hard to detect. So, the genetic structure of more common disorders plays a vital role in determining the influence of genetic variation patterns. In addition, the common variants present in a more ancient population give us tons of information regarding hereditary conditions found today. Common variant studies, however, cannot provide specific information as of now. So, it is also possible that a disorder may arise out of not one common variant but a combination of many variants. Further, this could affect the condition, its manifestation, and its distribution. Therefore, the population substructure is a field under genetics studies in which we study human genetics about the environment and health outcomes in this environment.