Biochemistry

Introduction to Genetics and Important terminologies used in genetics

Genetics and Important Terminologies Used in Genetics

The concept of genetics starts from the process of transmission of characteristics from parents to their offspring. Such transmission of characteristics is called inheritance. For more clear and better understanding, we can illustrate the fact with an example of a father, mother and their offspring. When we compare them, we can find some kinds of resemblances between either offspring and mother or father or among the offspring themselves. This is what genetics is all about.

The most modern concept or theory on genetics is Mendelian theory; however, there are many concepts from the era prior to Mendel such as moist vapor theory, fluid theory, preformation theory, epigenesis theory or pangenesis theory. Now with the development of  Mendelian theory, the pre-mendelian theory has almost been absolute

Here is the list of some important terminologies used in the study of Genetics

  1. Clones– Genetically uniform organisms produced from a single parent by asexual reproduction. They are also called carbon copy because of the fact that they look exactly the same as their parents.
  2. Offspring – The organism that is derived from two parents by sexual reproduction where genetic recombination causes variation is called offspring.
  3. Gene – DNA segment which is also called a functional unit of heredity.
  4. Allele – An alternative form of the same gene is called an allele. For example tt, Tt, etc
  5. Phenotype – The physical expression of and the organism is called phenotype. It is also called the observable phenomenon.
  6. Genotype – Genotype is the genetic makeup of an organism. It is a non-observable phenomenon.
  7. Dominant and Recessive – when there is a cross between two contrasting characters, they produce a heterozygote in their first generation. Among these two, one is able to express and the next is not able to express itself. The one that is able to express itself is called dominant and the other which is not able to express itself is called recessive.
  8. Homozygous – An individual with identical or similar alleles is called homozygous. For example tt, TT, YY, yy, etc.
  9. Heterozygous – An individual with the contrasting alleles is called heterozygous. For example Tt, Yy, etc.
  10. Parental Generation – The generation that is used as parents during crossing over to produce a progeny is called parental generation. It is designated by P1.
  11. Filial Generation – The progeny that is obtained as a result of the cross between the parents is called filial generation. They are usually designated by F1. Here the meaning of filial is offspring.
  12. Variation – The difference found among the organism is variation. It may be either somatic or germinal variation. Based on the degree of variation, it is of two types. A) Continuous Variation B) Discontinuous Variation
  13. Somatic variation – The variation that occurs in the somatic cells because of an environmental factor or any other factors like use or disuse of organs or something else is called somatic variation.
  14. Germination variation – The variations that are inherited from parents and do affect only the terminal or the reproductive cells is called germinal variation.
  15. Continuous Variation – The small, distinct, fluctuating and non-heritable variation that is unstable and does not have any role in evolution is called continuous variation.
  16. Discontinuous Variation – The large, distinct, stable and non-fluctuating variations that are heritable, stable, and have a significant role in evolution are called discontinuous variation.

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