Protein Synthesis, Landmarks of Medical Science | Science & Technology for UPSC CSE PDF Download

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For DNA’s control on enzyme synthesis (thereby heredity), the genes are copied in the form of three types of RNAs (Ribonucleic Acids): messenger RNA (mRNA), ribosomal RNA (rRNA), and transfer RNA (tRNA). The mRNA is so called because it carries the message from the DNA molecule for the synthesis of a protein or a polypeptide.  RNA and tRNA are named so because the former is acomponent of ribosomes, and the latter is involved in the transfer of amino acids to the site of protein synthesis. The process of their synthesis, using one of the DNA strands as a template is called transcription.

Translation

The mRNA is a coded message for the synthesis of a polypeptide. The process of decoding of the mRNA is called translation. The process involves all the three types of RNAs (mRNA, rRNA and tRNA) and some enzymes and protein factors (initiation, elongation, and termination factors).

Jumping Genes

Working on maize, Barbara McClintock reported in 1940s the presence of moveable genetic elements, which could detach from one site and move to new positions in either the same or different chromosomes. These elements, termed controlling elements by Dr McClintock, were shown to affect the expression of genes on either side of it, producing new phenotype. During the last two decades such mobile g enetic elements have been discovered in diverse organisms from bacteria to man. It has been found that these elements can freely move from one spot to another and have been variously called as transposable elements, transposons, insertion elements, or jumping genes.

Genetic Engineering

The process involves identification and isolation of a specific DNA sequence (gene/s) and its transfer usually to a bacterial cell for multiplication (gene cloning).The transfer is brought about through a bacteriophage or a plasmid (a small circular DNA in bacterial cytoplasm replicating independently) — called a vehicle or vector.

The sequence to be cloned may originate from any source (it could even be man made). There is promise that this technology can be used for the production of hormones, special proteins such as insulin or interferon (antiviral, anticancer protein) or antibodies. If these substances can be produced industrially on a large scale, medicine may be revolutionized as it was after the discovery of antibiotics. It should be possible through genetic engineering to produce various blood clotting factors, complement proteins (part of the immune system) and other substances for the amelioration of genetic deficiency diseases.

Theories of Evolution:

Lamarckism or the Theory of Lamarck: This theory was given by Lamarck in 1809, according to which the excessive use of an organ leads to its development and disuse causes its reduction.

According to Lamarck, the characters acquired by an individual from constant use are passed on to its offspring. Lamarck’s theory finds support from, stretched neck of giraffe, limblessness in snakes, webbed feet of ducks and blindness of moles etc. Lamarckism is criticised mainly for the inheritance of acquired characters.

Weismann’s Theory of Germplasm 

Weismann (1895) made a clear distinction between germ cells taking part in reproduction and the somatic cells. Weismann showed that the changes acquired by the somatic cells during the life time do not affect the germ cells, therefore, they do not reach the next generations. Weismann presented a modified view of Lamarck and held that only those changes which affect the germ cells in life time of an individual are passed on to the offsprings.
Darwin evaluated the significance of hereditary variations which reach from one generation to the other.Darwinism or Theory of Natural Selection

His theory of natural selection was published in 1859. The main postulates of Darwinism are:

(i) Each species produce offsprings in large number.

(ii) The variations exist among the members of any large species.

(iii) The production of offsprings in large numbers created intraspecific and interspecific competition.

(iv) Due to hard competition, only those individuals survive which can struggle successfully and the rest are destroyed. This is called the survival of the fittest.

De Vires Theory of Mutation

Mutation theory of organic evolution was proposed by Hugo De Vries in the year 1901 in his book “The Mutation Theory”. According to De Vries, mutations are the main source of variations which are responsible for appearance of new species from the old species. Recent studies have shown that mutations are not common in most plants, therefore, they can not be the chief cause of evolution. Thus the variation which De Vries observed generation after generation in Oenothera Iamarckiana are not mutations according to its modern definition but are chromosomal aberrations called heterozygous translocations.

Landmarks of Medical Science

Egyptian system The Egyptian system laboured under a heavy load of superstitions and magic, yet it developed many cures that have stood the test of time.

Pain-killing drugs and sedatives were well-known to the Egyptians. Henbane, a herb which is known as a sedative source was first used by the Egyptians, as a cure for scurvy and also as a cure for intestinal disorders.

The Chinese system

The first great medical treatise appeared in China around 450 B.C. This treatise unlike the Indian Rig Veda and Atharva Veda is an elaborate treatise on medicine. It included, among others, detailed description of acupuncture which has received international publicity during recent times. Between 600 and 900 A.D. the Chinese system of medicine known as HanYi, had spread to Korea and Japan and much of South-East Asia. Ephedra, a herb which soothes coughs, was known to the Chinese 4000 years ago.
Rhubarb, as a laxative, was firstused in China. Pumpkin seeds, another Chinese contribution, is a well known worm ridder. It is now found to be effective against snail fever also.

Greco-Roman

This system was almost entirely derived from the Egyptians. Scientific therapy started with Himppocrates. Under the Mughal Emperors, Arab medicine came to India. It took root in India, under the name of Unani, mainly because there was so much in common between the old system and new Unani system. The term Unani is derived from the Sanskrit Yavana meaning Greek. The Unani system continues to this day in India.

Ayurveda 

The Indian system known as Ayurveda originated as far back as 2000 B.C.
Ayurveda is a compound word in Sanskrit, literally meaning, the science of life. Actually it implies two connected ideas—the science of life and the art of living. Ayurveda, unlike allopathy or homeopathy, does not swear by any particular principle of cure. Ayurvedic treatments cover all the principles of allopathy, homeopathy and naturopathy.

Western System The western system of medicine was later named Homeopathy by Hahnemann. Homeopathy is based on the principle of ‘likes cure likes’ while allopathy is based on the principle that ‘opposites cure opposites’.