Genetics is the study of genes, heredity, and genetic variation in living organisms. It is generally considered a field of biology, but it intersects frequently with many of the life sciences. The word genetics stems from the Ancient Greek γενετικός genetikos meaning “genitive”/”generative”, which in turn derives from γένεσις genesis meaning “origin”.

Genetic processes work in combination with an organism’s environment and experiences to influence development and behavior, often referred to as nature versus nurture. The intra- or extra-cellular environment of a cell or organism may switch gene transcription on or off. A classic example is two seeds of genetically identical corn, one placed in a temperate climate and one in an arid climate. While the average height of the two corn stalks may be genetically determined to be equal, the one in the arid climate only grows to half the height of the one in the temperate climate, due to lack of water and nutrients in its environment.

KEY POINTS: The father of genetics is Gregor Mendel, a late 19th-century scientist and Augustinian friar.

Although genes were known to exist on chromosomes, chromosomes are composed of both protein and DNA, and scientists did not know which of the two is responsible for inheritance. In 1928, Frederick Griffith discovered the phenomenon of transformation (see Griffith’s experiment): dead bacteria could transfer genetic material to “transform” other still-living bacteria. Sixteen years later, in 1944, the Avery–MacLeod–McCarty experiment identified DNA as the molecule responsible for transformation. The role of the nucleus as the repository of genetic information in eukaryotes had been established by Hämmerling in 1943 in his work on the single celled alga Acetabularia. The Hershey–Chase experiment in 1952 confirmed that DNA (rather than protein) is the genetic material of the viruses that infect bacteria, providing further evidence that DNA is the molecule responsible for inheritance.


A genetic disorder is a disease that is caused by an abnormality in an individual’s DNA. Abnormalities can be as small as a single-base mutation in just one gene, or they can involve the addition or subtraction of entire chromosomes.

KEY: DNA is deoxyribonucleic acid. It is the molecule that contains the genetic code of organisms. This includes animals, plants, protists, archaea and bacteria.

Genetic disorders may or may not be heritable, i.e., passed down from the parents’ genes. In non-heritable genetic disorders, defects may be caused by new mutations or changes to the DNA. In such cases, the defect will only be heritable if it occurs in the germ line.


There are different types of genetic disorder, some of which includes:

  1. Single-Gene Disorders: These disorders involve mutations in the DNA sequences of single genes. As a result, the protein the gene codes for is either altered or missing. some examples of single – Gene disorder are;Adenosine deaminase (ADA) deficiency, Alpha-1 Antitrypsin Deficiency,Cystic Fibrosis,Galactosemia,
    Huntington’s Disease, Maple Syrup Urine Disease (MSUD),Neurofibromatosis Type 1,Pachyonychia Congenita , Phenylketonuria, Severe Combined Immunodeficiency , Sickle Cell Disease, Smith-Lemli-Opitz Syndrome .





2. Chromosomal Abnormalities: In these disorders, entire chromosomes, or large segments of them, are missing, duplicated, or otherwise altered. Examples include; Cri-du-Chat Syndrome, Down Syndrome, 47, XXY (Klinefelter syndrome),Turner Syndrome, and Williams Syndrome.








3. Multifactorial Disorders: These disorders involve variations in multiple genes, often coupled with environmental causes. Examples include; Diabetes, Hypertension, Alzheimers Disease, Breast/Ovarian Cancer, Colon Cancer, Hypothyroidism, etc.


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