Many people are born with and suffer from diseases such as sickle cell anaemia, haemophilia, severe combined immuno deficiency (SCID), and colour blindness. Such diseases are caused due to genetic defects. These genetic defects are hereditary.

Genetic disorders occur when a mutation (a harmful change to a gene, also known as a pathogenic variant) affects your genes or when you have the wrong amount of genetic material.

It has been estimated that around 2000 children in India alone are born every day with genetic disorders.

GENE FUNCTIONING

Genes play a number of different roles in the proper functioning of an organism by

(a) controlling synthesis of enzymes involved in biochemical reactions,

(b)regulating their synthesis such that the right enzyme appears at the right time.

GENETIC DEFECT

Sometimes genes may not function properly due to some irregularity or defect in their structure. This may lead to genetic disorders. A defective gene may appear in an individual in the following two ways:

(i) Certain defective genes are inherited and the defect runs in the family. For example : Colour blindness, haemophilia, sickle cell anaemia.

(ii) A gene becomes defective all of a sudden due to mutation during early development. For example : Albinism (non-heritable).

A gene mutation may alter the synthesis or activity of an enzyme needed for the normal completion of chemical reactions or for the normal functioning of an organism

TYPES OF GENETIC DISORDERS

1 . Chromosomal

This type affects the structures that hold your genes/DNA within each cell (chromosomes). With these conditions, people are missing or have duplicated chromosome material.

Examples: Down syndrome (Trisomy 21), FragileX syndrome, Klinefelter syndrome, Triple-X syndrome, Turner syndrome, Trisomy 18, Trisomy 13.

2 . Complex (multifactorial)

These disorders stem from a combination of gene mutations and other factors. They include chemical exposure, diet, certain medications and tobacco or alcohol use.

Examples: Late-onset Alzheimer’s disease, Arthritis, Autism spectrum disorder, in most cases, Cancer, in most cases, Coronary artery disease, Diabetes, Migraine headaches, Spina bifida, Isolated congenital heart defects.

3 . Single-gene (monogenic)

This group of conditions occurs from a single gene mutation.

Examples: Cystic fibrosis, Deafness that’s present at birth (congenital), Duchenne muscular dystrophy, Familial hypercholesterolemia, a type of high cholesterol disease, Hemochromatosis (iron overload), Neurofibromatosis type 1 (NF1), Sickle cell disease, Tay-Sachs disease.

CONSEQUENCES OF GENETIC DEFECTS

Under normal conditions, genes work in total harmony completing their specific job of converting a raw material into a finished product, by synthesising the specific enzyme. But defects in them leads to –

(i) accumulation of the metabolic substances that are toxic, or

(ii) deficiency of a compound that is important for normal cell functioning.

There are mutations that can lead to disorders in any part of the body, including muscles, eyes, liver, bones, kidneys, nerves, and blood system.