There are many words that start with the root term ‘geno’ or ‘gen’. The meaning of this prefix in Greek and Latin is race, kind, family or birth. Some of the common words starting with ‘geno’ in Biology are genotoxicity, genotropism, genocopy, genoblast, and genophore.
Genotoxicity, in genetics, means the property of a class of chemical agents that causes mutation of the genetic material within a cell leading to cancer. Genotropism is the reciprocal attraction between the carriers of the same or related latent recessive genes. Genocopy is the phenotypic copy of a genetic trait caused by an unalike genotype. Genoblast is the bisexual nucleus of a fertilized ovum. And finally, genophore is the genetic structure of a prokaryotic cell, organelle, or plastid. All these terms have been explained below in detail.
Genotoxicity tests are designed to detect drugs which can induce genetic damage directly or indirectly by various mechanisms of action.
Genotoxicity is the property of an agent (chemical) to cause damage to the genetic information, thereby causing mutations that may lead to cancer. These chemicals damage the genetic information within a cell resulting in mutations which may lead to malignancies or heritable defects.
Genotoxicity assays have different endpoints, such as single- and double-strand breaks, point mutations, deletions, chromosomal aberrations, micronuclei formation, DNA repair and cell-cycle interactions. These endpoints are related to genotoxicity in vitro (human and mammalian cells) as well as in vivo (population biomonitoring and animal studies). Use of the same end-points in various biological systems in different species enables comparison of interspecies effects. In vitro genotoxicity assays represent simple, robust and time- and cost-effective testing of targeted toxicity and underlying mechanisms.
The Ames test (bacterial reverse mutation assay) is the most commonly used genotoxicity assay in regulatory toxicology. It is based on the induction of reverse mutation in the histidine gene, which enables the bacteria to synthesize histidine and form visible colonies in minimal histidine medium. The chromosomal aberration test is often applied in mammalian systems, both in vitro and in vivo, and has been used also for testing of genotoxicity. The comet assay or single cell gel electrophoresis is one of the most common tests for exploring the genotoxic potential.
The ISO guidelines for genotoxicity testing require examination of gene mutation (bacterial mutagenicity test), chromosomal aberrations (chromosomal aberration assay) and DNA effects (mouse lymphoma assay). The FDA also requires three genotoxicity tests. The bacterial reverse mutation and the in vitro mouse lymphoma tests are the same as those recommended by ISO. A third test, which some within the FDA recommends, is an in vivo test, such as the mouse micronucleus test.
The doctrine first proposed by the Hungarian geneticist Leopold (Lipot) Szondi (1893–1986) in the journal Acta Psychologica in 1938 and developed further in 1944 in his book entitled Schicksalsanalyse (Analysis of Destiny), that latent recessive genes determine instinctive or spontaneous choices (in love, friendship, occupation, illness, and even manner of death) and underlie attraction between people sharing the same genes. Szondi believed that these genes regulated the "possibilities of fate" and was the working principle of the familial unconscious.
Genotropism is the reciprocal attraction between carriers of the same or latent recessive gene. The term was coined by Léopold Szondi.
The ‘Szondi-Test’ is a psychological test. It was developed by Hungarian geneticist and psychoanalyst Leopold Szondi (1893-1986). The test identifies psychological traits within patients, such as depression or mania. This example was used by the controversial psychiatrist and medical author Dr Ann Dally (1929-2007) within her private practice. The test consists of 48 headshots that show distinct facial expressions. The patient is shown a row of eight images and instinctively chooses the two friendliest people. They then choose the two unfriendliest from the remaining six images, then the two most unpleasant faces from the remaining four. The psychologist notes the number on the reverse of each picture and analyses the result. This test is based on the theory called genotropism. This argues similar people attract each other as ‘like attracts like’. The patient highlights certain character traits that apply to them by selecting images they subconsciously identify with themselves.
Szondi also defined a series of so-called “drive needs” that therapists could use to measure the patient’s choices:
The h-drive need (for hermaphrodites or homosexuals).
The sadist drive needs.
The e-drive need (named after epilepsy).
The hysteric drive needs.
The catatonic drive needs.
The paranoid drive needs.
The depressive drive needs.
The maniac drive needs.
The genes of your ancestors are present in your unconscious and determine your choices.
This connection often brings unhappiness or even inherited disorders, impulses, and instincts.
Thus, if you’re able to connect to your “family unconscious”, you’ll be able to identify the hindrances that are holding you back. Once you detect them, you can free yourself from them
While Szondi accepted the Oedipus complex, he found that it existed only under the following conditions: when the mother sees her father or brother represented in her son, or when the father sees his mother or sister in his daughter. Therefore, the son takes after the genes represented in his maternal grandfather or uncles, and the daughter after her paternal grandmother or aunt
Today, this concept is obsolete; however, it has been interpreted in revised forms through studies like psychopathology and homogamy.
Genocopy is a phenotypic trait that is basically a copy of a phenotype but is the result of a different genotype.
Genocopy is a trait that is a phenotypic copy of a genetic trait but is caused by a different genotype. When a genetic mutation or genotype in one locus results in a phenotype similar to one that is known to be caused by another mutation or genotype in another locus, it is said to be a genocopy.
Inherited Deafness - where the mutation of any of the dozens of genes critical for the process of perceiving sound will lead to loss of hearing.
Mitochondrial Diseases - identical Mitochondrial DNA mutations may not show up as identical diseases. Genocopies are often seen as diseases that might be caused due to the same mutation which results in non-identical expression.
The genocopy event between TBX1 and 22q11.2 mutations is one that shows grave symptoms. The 22q11.2 mutation leads to DiGeorge or velocardiofacial syndromes. Similarly, the mutations in the TBX1 genome exhibit the same symptoms.
Genoblast refers to the nucleus of a fertilized oocyte. It is the bisexual nucleus of an impregnated ovum, regarded as composed of a female part, feminonucleus ( female pronucleus ), and of a male part, masculonucleus ( male pronucleus ).
It is also called a prokaryotic chromosome.
Genophore refers to the genetic material of a prokaryote. It is the structure that carries the genetic material within a cell, organelle, or virus. In other terms, the simple DNA strand of a prokaryote or plastid is known as genophore.
The term “chromosome,” in the case of a prokaryotic organism is misleading because the genophore lacks chromatin. The genophore is compacted through a mechanism known as supercoiling, but a chromosome is additionally compacted through the use of chromatin. The genophore is circular in most prokaryotes and linear in very few. The circular nature of the genophore allows replication to occur without telomeres. Genophores are generally of a much smaller size than Eukaryotic chromosomes. A genophore can be as small as 580,073 base pairs (Mycoplasma genitalium). Many eukaryotes (such as plants and animals) carry genophores in organelles such as mitochondria and chloroplasts. These organelles are very similar to true prokaryotes.
It carries the genetic information in a prokaryotic cell that is transmitted via cell division or binary fission to the next batch (or generation) of cells.
1. What is the difference between genotoxic and carcinogen?
The term "genotoxic carcinogen" indicates a chemical capable of producing cancer by directly altering the genetic material of target cells, while "non-genotoxic carcinogen" represents a chemical capable of producing cancer by some secondary mechanism not related to direct gene damage.
Thus all genotoxic substances are carcinogens nut all carcinogens are not genotoxic.
2. Name a few genotoxic testing methods.
Few genotoxic testing methods are Ames test, chromosomal aberration test, comet assay or single cell gel electrophoresis.
3. What is the difference between genocopy and phenocopy?
Genocopy is a trait that is a phenotypic copy of a genetic trait but is caused by a different genotype while phenocopy is a variation in an organism that resembles a genetic one, but has an environmental rather than a genetic cause, and is not inherited.
4. Describe the Sczondi test based on the theory of Genotropism?
Léopold Szondi invented a projective test using photographs of people with mental pathologies to determine the unconscious, ancestral illnesses (or aptitudes) of his subjects. Szondi’s images were garnered from psychiatric textbooks published around 1900. Such photographs presumably revealed unconscious thoughts, desires, and destinies in the course of a test session. If a patient responded positively to a photo-portrait of a diagnosed ‘hysteric’, for instance, this indicated that the subject herself had unconscious, inherited hysterical traits. Szondi’s reasoning was predicated upon two commonly held fallacies: first that an individual’s physical appearance is the external marker of mental life, and second that photography is a transparent means of revealing true facts. This test is based on the theory called genotropism which states similar people attract each other as ‘like attracts like’.