Every living organism is made up of cells. At fertilisation, human baby has only one cell at first known as a zygote. It gets divided forming multiple cell clusters. Every gene is copied, giving each new cell a complete package of the genetic material—the genome.
Considering the fact that, there are roughly 10 trillion cells in the human body, the technique of genome copying is extremely amazing.
The genome is organised into chromosomes, which contain genes, and is composed of a chemical called DNA, (deoxyribonucleic acid.)
Chromosome
Nearly every cell in our body contains tightly wound bundles of DNA called chromosomes. In humans there are 23 pairs of chromosomes - 22 autosomes and one pair of sex chromosomes (XX in a female and XY in a male). One chromosome in each pair is inherited from our mother and the other from our father.
Each chromosome has hundreds of genes working singularly or collectively to carry out our body functions.
DNA
Our individual genetic information (instruction manual) is found in the lengthy molecule known as DNA. It contains the directions for generating every protein in our bodies, much like a recipe book.
DNA is made up of two strands that intertwine to produce a double helix shape that resembles a spiral staircase. Backbone of each strand is made up of sugar and phosphate groups and four fundamental building units, or "bases," make up each strand of DNA: Adenine, Cytosine, Guanine, and Thymine (ATGC). A connects with T and G with C forming the rungs of the ladder.
The 3 billion bases of DNA molecule in the body store information about our health including the potential risk of a genetic condition to individual and even the progeny.
Gene
The sections of DNA are known as genes. They contain the sets of instructions to produce one specific molecule in our body, usually a protein.
The genetic language has just 4 letters - ATGC called as bases or nucleotides and their sequential arrangement is known as ‘DNA sequence’. These bases form words with three alphabets (triplet code) called a codon. A string of codons may look like this: ATC TGA GGA AAT GAC CAG.
Each trio of letters identify a different amino acid, which makes up the building blocks of proteins.The majority of cellular activity is performed by these proteins which are also essential for the regulation, structure, and operation of the body's tissues and organs.
In response to the needs of our bodies, various codons are read at various times in various cells. With a variety of permutations and combinations they make up functional genes carrying meaningful instructions. About 20,687 functional genes are found in the human genome.
Thus, everything is governed by our genes. Every cell is aware of what it should "be" since a gene tells it what to "become, where, and when."
Today, with continued genetic advances, and technological innovations the entire human genome is sequenced (Human Genome Project 2003) giving special attention to genes that cause or may predispose to disease. Now we can identify the precise role of genes responsible for most of our body structure, functions and diseases. With the emergence of the biotechnology industry these findings have rapidly being translated into widely available tests and diagnostic products.
Mutation
Over the course of a lifetime, DNA may experience alterations or variations (mutations) that lead to changes in the DNA sequence. The codon flow gets disrupted, and any missing or repeated base alter our body functions impacting the production of proteins and results can be disastrous.
This can be because of a natural consequence of errors in DNA replication and/or experiencing environmental elements like smoking, drugs, radiation etc.
When mutations exist in the sperm, or eggs, they can also be inherited. Generally, our cells recognise and rectify mutations. However, if they are not repaired, the gene may send improper instructions to the body, which can result in a genetic disorder.
Congenital changes in the number or structure of chromosomes can cause chromosomal disorders. When there are more or fewer copies of a specific chromosome than expected, the number of chromosomes changes. When the components of a single chromosome are disturbed, deleted, duplicated, or translocated changes in chromosome structure result.
Mutation in a single gene is known as single gene disorder. This can affect many body systems or variations in multiple genes can disrupt one body system. The majority of single gene diseases start early in childhood, but certain inherited conditions and numerous other disorders with genetic aspects start considerably later in life (diabetes mellitus or mental illness). Then there are numerous conditions where both hereditary and environmental variables have a significant impact (coronary heart disease, hypertension). These multifactorial or complex disorders are more prevalent than single-gene diseases, and as a result they pose a bigger burden on public health.
Genetic Testing
The genetic tests are based on the analysis of the chromosomes and or examination of the DNA by various chromosomal and molecular testing. They help in diagnosis, prognosis of a medical condition or determine the carrier status of an individual or can predict potential risk of developing a condition later in life. If we get an idea about the likely onset of the disorder (eg: adult muscular dystrophies) we can choose appropriate treatment options or gauge the risk of its transmission to the progeny. Given that genetic disorders frequently run-in families, other family members may find it valuable to know the patient’s genetic make-up. They could find this information useful for their own health care.
Early cancer detection has undergone a revolution with the use of DNA testing to look for early mutational events that predispose to a variety of prevalent malignancies in different bodily tissues.
However, the tests should be accurate, sensitive, specific and performed with appropriate informed written consent for which each test needs pre-test or post-test genetic counselling.
The tests are classified as Screening & Diagnostic and can be offered at preconception, prenatal or postnatal stages on various body tissues.These High-quality tests (of high specificity and sensitivity) are performed with the highest level of proficiency and interpreted correctly.
A few major differences between pathological testing and genetic testing
It is imperative to have a confirmatory test to each screening test.
Pre-conceptional/Prenatal / Preimplantation stage
In high-risk cases prenatal diagnosis is offered with Chorionic Villus Sampling & Amniocentesis. In IVF through testing of embryos (PGT-A, PGT-M, PGTstr ) before implanting can be availed.
If you are planning a pregnancy, please contact your doctor without further delay. If you have any of the following indications:
Conclusion
When compared to common diseases in the general population, genetic conditions though appear individually rare are collectively more. Most are heritable, chronic with life limiting from fetal stage. They can be the cause of infertility or even cancers.
The absence of a diagnosis initiates a family's herculean trek from pillar to post. However, many disorders are of variable and often unpredictable severity. Certain environmental factors may interact with only one set of genes and not with another. But the genetic testing can provide accurate diagnosis, prognosis, management, and prevention.
In general, very few disorders are treatable but almost all are preventable, and an early diagnosis can prevent the financial, social and psychological repercussions affecting the entire family.
Thus, understanding our genetic makeup is the need of the day as genetics has marched through scientific research in identifying disease causing genes and entered where extended laboratory tests at DNA level can lead to personalised medicines.
The footsteps now are in therapeutics wherein it is possible to identify genetic response to the drug metabolism, to common disorders, and accordingly tailor-made treatment for genetic conditions can be provided. Future studies might produce psychological or pharmaceutical therapies that can reduce, postpone or even prevent the development of all these disorders.
However, genetic testing is not an end in itself but it is a tool for gathering knowledge and insight to assist people in making decisions about their own and their families' health.
Genetic consultants are medical specialists with expertise in the evaluation, diagnosis, and management of at-risk or affected people and families with genetic diseases through genetic counselling. They are skilled at presenting unbiased, moral, and accurate information in a clear and concise manner and have in-depth understanding of applicable available tests.
Genetic counsellors have a master’s degree that focuses on genetics and counselling skills.
Non-directive genetic counselling should help the patient in making educated decisions on their own while also offering compassionate and understanding support. At the same time, voluntariness, informed consent, and confidentiality of genetic information should be protected.
Through genetic education that is pertinent to the patient's requirements and concerns, genetic counselling includes explaining to clients:
Genetic consultation enables individuals and family members recognise and navigate their anxiety about hereditary disorders and related health risks and adapt to genetic risk factors accurately and proactively.
With the mapping of the human genome project in 2003 the role of genetic counselling has increased further both in scope and importance.
Details required at the pre-test session: (both the partners)
During post-test session:
In case of normal results further follow up is suggested.
If there is any abnormality, the patient is given alternative options to consider for further investigation/management.
All the pros and cons are explained to the patient along with clear appreciation of the short-term and long-term consequences of the options.
Conclusion
Around the turn of the 20th century, the practice of counselling people on inherited traits began, and now, with scientific and technological developments genetic testing has gained popularity, and an increasing number of companies are offering rapid, affordable tests. Compared to many other types of medical information, genetic insight involves additional concerns and burdens for the individual, the family, and society. This creates a significant issue because it is so simple to obtain these outcomes, but many people may feel at a loss as they themselves cannot interpret the reports of the tests.
Numerous distinct emotions can be brought on by having a genetic disease: early shock and denial guilt, concern, grief, wrath, and unease are all fairly typical emotions that can have a significant impact on both individuals and families.
The genetic counsellor helps people assess the consequences of genetic testing and genetic information and assess what level of risk they are willing to take. Therefore, guiding the patient in a non-directive manner in making informed choices is a part of genetic counselling - may it be the testing itself or reproductive options. However, since risk perceptions vary what is ideal for one person may not be suitable for another. Patients need to be supported by the genetic counsellor in making the best decision for themselves.
Ultimately it is the patient/family who judges the risk involved and makes the decision.
Disclaimer: The website is not intended to be a substitute for the medical advice of a physician/ geneticist.
for diagnosis or treatment of any medical or genetic condition or drug/supplement intake, consult a physician.