Top 10 Basic Terminologies in Genetics | Basic Genetic Concepts & Terms
Genetics is the branch of Biology in which we deal with the study of gene and their variation from parents to offspring. There are many terminologies in genetics, the father of genetics was Gregor Mendel, who studied genetics a lot, and his experimental result was in statistics; he was the first to explain genetics in statistical form.
He used pea plants for his experiment and observed seven-character in pea plants. The laws of Mendel give a base to the study of genetics, i.e., the law of segregation and the law of independent assortment.
The Contribution Of Some Scientists Are:
He is called the father of genetics; he discovered the principle of heredity by experimenting on pea plants before discovering genes and DNA. He said that genes occur in pairs from parents, which unite together during fertilization.
Sir Ian Wilmut
He was a British biologist who discovered a dolly sheep through the cloning process for the first time. He uses the transfer of genetic material between different sheep. For this, he was awarded Noble Prize. He is known as the father of cloning.
Thomas Hunt Morgan
He was an American geneticist who discovered the chromosomal theory of heredity by an experiment on the fruit fly (drosophila). He explains that genes are linked together on chromosomes and are responsible for heredity. Here are the top 10 basic terminologies in Genetics:
Epistasis means standing upon. The process in which the effect caused by one gene at one locus is suppressed or hides the effect produced by another gene on another locus. In such interaction, the suppressed gene is called hypostasis, and the gene which suppressed is called Epistasis.
It can be defined as the phenomenon in which another gene controls the expression of one gene. It is an example of non-allelic interaction. There is a difference between Epistasis and dominance; in dominance, the relationship is between the same gene on the same locus. In Epistasis, the interaction is in between different genes at another locus.
The abrupt or sudden change in the sequence of DNA nucleotides during cell division is called a mutation. It results from radiation, mutagens (physical or chemical), or virus attacks. Some mutations are rare, while others are common mutations that occur in more than one percent of the population is called polymorphism.
Origin Of Mutation
Mutation occurs in two ways either it is transferred from the parent or either it occurs in an individual lifetime. Mutation inherited from parents to offspring is called heredity or germline mutation, as this mutation occurs in egg or sperm cells. Mutation after fertilization is called a new mutation (de novo mutation).
While the mutation that occurs in the person’s DNA at any time of life is called an acquired mutation, these changes are due to the environment or UV rays. Therefore, acquired mutation cannot be passed from generation to generation.
Types Of Mutations
The mutation which occurs naturally due to internal factors is called spontaneous mutation. In contrast, that mutation which is happened by an external factor is called an induced mutation based on where mutation and what extent of mutation occur.
Mutations are of two types: the mutation in which one nucleotide or some nucleotide changes in DNA is called a point mutation. Point mutation is a sudden change that can change the individual’s phenotype. In comparison, the mutation that causes a difference in the structure and number of chromosomes is called a chromosomal mutation.
Point mutation occurs in the following ways;
- Deletion – It is the removal of nucleotide from DNA strand.
- Insertion – It is the addition of a nucleotide to a particular segment of DNA.
- Substitution – It is the replacement of nucleotide in a DNA strand.
Structural mutation or chromosomal mutation also occurs in the following ways;
- Inversion – It is the change of position of nucleotide.
- Translocation – It is the shifting of the segment of a chromosome to a non-homologous chromosome, thus affecting both the chromosomes.
- Duplication – It is the repetition of the gene in the same chromosome.
There is another aspect of mutation in chromosomal mutation; one is aneuploidy, the other is euploidy. Aneuploidy is further divided into; monosomy, nullisomy, trisomy, tetrasomy.
In codominant, both versions of the gene are expressed equally. As in dominant and recessive, one gene will be completely dominant, and the other will be suppressed entirely, but both will express themselves in codominance.
For example, the cross of the 4 o’clock flower is an example of codominant in which red flower is crossed with white flower. Still, in the F1 generation, pink also appears, resulting from codominance. The same condition can be seen in the human blood group system; the blood group AB has resulted from codominance in which both the A and B are equally contributed.
A recessive trait is inherited or expressed when it is a homozygous condition. It may remain in the heterozygous state, but it will not be described in that condition. An example of a recessive trait is sickle cell anemia, in which the individual inherits both the copies from either parent as mutated, so the individual becomes sickle cell anemic.
In this disease, the shape of RBC becomes the sickle shape and cannot transport oxygen. The attached and detached ear lobe is also an example of a recessive trait; if the individual has homozygous ee, the ear lobed will be attached; otherwise, the ear lobe will be detached in Ee or EE form. The same thing can be observed in the Mendel experiment in which the dwarf height has both the gene is in the homozygous form which was tt.
It is a phenomenon in genetics in which one type of gene or allele on the chromosome is dominant or overriding on the allele of the same kind of gene. Individuals inherit two versions of the gene, called an allele, from their parents so that one will be dominant over another.
The chromosome occurs in pairs in humans, so it has two genes; one of the alleles will be dominant. If we take an example of Mendel’s experiment in which he crosses tall and dwarf plants. The tall plant was represented by T, and the short or dwarf plant was described by t. The result of the F1 generation was all tall, either in the form of TT or Tt. So it means the tall T is dominant over dwarf t. That’s why the result was that all plants were tall.
Phenotypes are the set of observable characteristics, an individual’s physical appearance like eye color, height, hair structure, etc. Phenotype refers to the structural or morphological form of an organism. As in Mendel’s experiment, the physical appearance or phenotype of pea plants was the height of the plant, color of seed, pod shape, flower color, etc.
Phenotype is affected by the influence of the environment, for example, one who eats, the one who exercises, one who smokes. Therefore, all the factors will affect their phenotype. However, there is also a relation between genotype and phenotype.
The arrangement of genes of an individual is called genotype, as genes are present on DNA, so simply, it is the form of DNA. A large amount of DNA is typical in all; that is why we all are the same, but there is a difference among us it is due to the arrangement or sequence of genes.
For example, if a child has the brown color of the eye, it means it is heterozygous, i.e., a different allele. If a child has blue eyes so its means it is homozygous. As Mendel’s experiment show genotype in the form of 3:1 (the result of the law of segregation) in the same manner, the genotype in the law of independent assortment was 9:3:3:1.
3. Locus (plural loci)
Locus is a specific or marked position on the chromosome where the gene is located. Every chromosome has many genes which are located in a different place. Each gene occupies a specific locus; each locus has an allelic form that collectively makes the individual’s genotype.
The alternate form of the gene is present in the same position on the chromosome. Allele plays a role in the appearance of the physical structure called the phenotype. Every person inherits two alleles for each gene from their parent, one from mother and one from father.
If both alleles are the same, then the individual will be homozygous, but if both alleles are different, the individual will be heterozygous for that character. So, for example, the ABO blood group is controlled by the ABO gene, and there are six alleles for this gene.
Bateson first used the word gene publicly; Mendel called it factor. Gene is the basic structural and functional unit of heredity. Gene is located in DNA which consists of nucleotides arranged linearly. It transfers character from parent to offspring. Everybody consists of two copies of the gene from either parent, i.e., genes always occur in pairs. Many genes are responsible for protein synthesis or a specific character.
So, these are the top 10 basic terminologies in genetics, and all these help us a better understanding of genetics.