MORE ON GENES- II

 MORE ON GENES- II

Having known that 2 major types of gene sources are father and mother, very little is known of the fate of the critical balancing between structural and functional genes.Neither of them can work independent of the other There is such a fine co-ordination among them that they are inseparably intertwined by feed-back regulation of each other.

Now on to Functional proteins

Functional proteins - as the name suggests do not add to structure; instead they are responsible for chemical activity in cells by enzymes or secretions, leading to metabolic functions.  By metabolic functions- events like Respiration / Digestion/ Assimilation are carried out in special organs; their functions are coordinated by signals between respiration, digestion and circulation. Functional proteins can   trigger changes in structure of the organism through hormonal modulation. The hormones work in reproductive cycles and bring about physiological changes which may reflect as physical changes. Among the functional proteins, the most important are Enzymes; they catalyze a variety of changes in biochemical molecules in our systems and set off physico-chemical alterations without even the individual recognizing those changes. Through all our life, we keep changing; but seldom do we feel or recognize the same.

Defective genes = Defective products. Obviously, biological processes are much like culinary recipes in that the quality of the final product largely rests on the quality of the ingredients. With bad ingredients good end product would be just a far cry; likewise, when genes are defective, the end products                 [proteins] would also be bad and bad proteins cannot yield normal tissues or structures. This is the relationship between gene and its products. In the early part of the topic, it was made clear that all our structures are gene-derived proteins.

Proteins are Amino acid -derived. A set of amino acids together form a protein. Right proteins have the right amino acids. Each amino acid is derived from Translation of RNA- sequences [m-RNA= messenger RNA]. Each m-RNA  molecule is a copy from DNA template. This copying step is TRANSCRIPTION.  DNA by transcription delivers m-RNA; m-RNA by translation of its bases gives rise to amino acids ; the amino acid so derived is from reading 3 successive codes on the m-RNA molecule. Thus, the protein language is formed of 3 lettered codes called triplet codes. Normally codes are steady; sometimes codes may suffer by addition or deletion of 1 base or more in a long sequence; adding or removing of  one letter from a series can seriously alter meaning of statements in a DNA  molecule, because every three letters are taken to be a word. Addition or deletion can alter the sequence of statements as every three letters together form a ‘word’ leading to  some amino acid. Use the following example to understand the reading of frames in m- RNA for translation

THE BAD DOG DID ALL THE BAD = makes a meaningful reading /statement   Instead a modification by deletion  replaces ‘THE’ by ‘A’  and becomes  ABADDOGDIDALLTHEBAD Now read 3 letter frames beginning on A .  = ABA DDO  GDI  DAL  LTH  EBA  D .. = meaningless protein series or defective product.

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Prof. K. Raman