Human Genetics

Human genetics, also known as genetics, is the study of heredity. Genetics completely deals with DNA. Gregor Mendel, a Moravian monk, is called the “Father of Genetics”. Human genetics is basically about the passage of genetic information from one generation to another, from parents to kids. The experiment performed by Mendel between 1856 and 1863 with pea plants has opened new gates for the development of genetics. After his findings, developmental studies in genetics have paved a long path of research and findings. In this blog, we will learn in detail about human genetics terminology, the Centre for Human Genetics, subfields of human genetics, human genetic disorders, and human genetic diseases. 

Basic genetic terms:

DNA: Deoxyribonucleic acid stores the genetic information of an organism. 

Gene: Unit of heredity, composed of DNA.

Allele: Different possible forms of a single gene. 

Genome: Collection of all genes in a person. 

Chromosome: Component of a cell made up of DNA and proteins. 23 pairs of chromosomes are present in a single cell.

Mutation: Undesired changes that occur in a cell among the genes, chromosomes, or DNA. 

Subfields of Human Genetics:

Human genetics is a vast field that encloses a wide range of several areas. They are:

• Behavioural Genetics 

• Biochemical Genetics 

• Cancer Genetics

• Classical Genetics 

• Clinical Genetics

• Cytogenetics

• Developmental Genetics

• Ecogenetics

• Epigenetics

• Forensic Genetics

• Immunogenetics

• Molecular Genetics 

• Pharmacogenetics

• Phylogenetics

• Population Genetics 

• Quantitative Genetics 

Centre for Human Genetics :

The Centre for Human Genetics (CHG) of India is located in Bangalore, Karnataka. It is an advanced research centre for genetics, focusing on human disease. It provides training, advanced research, and education in disease-based genomics. The Centre for Human Genetics has performed various genetics research on diseases like cancer, heart disease, skin diseases, and diabetes. 

Classification of human genetic disorders:

A human genetic disorder or human genetic disease is caused by some abnormality in the genes of an individual. Genetic disorders are classified into two types based on their occurrence. They are:

• Gene Mutation is undesirable changes occurring in the genes that are called Gene mutation. It is divided into two types:

• Single Gene Disorder
• Polygenic Disorder

• Chromosomal aberrations are structural and functional changes in the chromosome. It is categorised into two types: 

• Structural chromosomal defects
• Numerical chromosomal defects.

Human genetic diseases:

There are about 6,000 genetic diseases identified in humans. The causation of genetic disorders is influenced by various factors like medications, drugs, mutations, chemicals, heredity, environment, etc.

Some of the more commonly known genetic disorders are listed below:

• Down Syndrome is also called Trisomy 21. It is a chromosomal disorder that affects chromosome number 21. This occurs when extra genetic material is added to the chromosome due to some abnormal replication. 

• Fragile X syndrome is familiarly known as Martin-Bell Syndrome. Mutation in the FMR1 gene (fragile X mental retardation 1 gene) is found to be the major cause of Fragile X Syndrome. This genetic disorder mostly affects males more than females. 

• Klinefelter syndrome is also called XXY syndrome. This occurs when a male has an extra X chromosome. It is not an inherited disease and occurs as an error within the genes. It is a consequence of a genetic error post-fertilization. 

• Triple X syndrome also called Trisomy 47, is caused by the occurrence of an extra X chromosome in females. It occurs due to the deformed egg or sperm during the baby’s development in the womb.

• Turner syndrome is also known as Gonadal dysgenesis. Here, the female has only a single X chromosome. It is characterised by the absence of an X chromosome. The major causes of Turner syndrome are monosomy, mosaicism, and X or Y chromosomal alterations. 

• Cystic fibrosis is a lethal disorder caused by mutations in the CFTR gene (Cystic fibrosis transmembrane conductance regulator gene). It causes severe damage to the lungs and digestive system. This also affects the pancreas, kidneys, intestines, and liver.

• Sickle cell anaemia is a type of inherited disease caused by a mutation in the HBB gene. It results in a deformed RBC that cannot facilitate oxygen transport in the body. This can cause heart disease, organ failure, blindness, etc. 

• Tay Sachs disease, also called GM2 gangliosidosis, affects nerve cells. This genetic disease is caused by a mutation in the HEXA gene (Hexosaminidase A) that results in the inadequacy of the beta-hexosaminidase A enzyme. 

• Huntington’s Disease is caused by a flawed gene present on chromosome 4. It is an autosomal dominant disorder. This results in damaged nerve cells that impact brain functions. This genetic disorder occurs in five stages. 

• Thalassemia is a blood-related disorder caused by mutations in the α-globin gene on chromosome 16 and the β-globin gene on chromosome 11. It is an autosomal recessive disease that results in reduced synthesis of haemoglobin and RBC. 

Conclusion:

Exploration in Human Genetics is never-ending. Understanding more deeply about human genetics can help us cure existing genetic disorders and can also pave the way for various advancements in the field of genetics like medicine, research, evolution, health, environment, industry, etc. The future aspect of human genetics aims to open new gates in medicine by being the cure for untreatable disorders.