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Use of Polymerase Chain Reaction ( PCR )
- PCR is a technique by which any piece of DNA can be quickly amplified ( copied many times ) without using cells.
- The DNA is incubated in a test tube with a special kind of DNA polymerase enzyme, a mixture of deoxyribonuleotides for use as raw material, and short pieces of synthetic single stranded DNA to serve as primers for DNA synthesis.
- PCR can make billions of copies of a DNA segment in a few hours.
- To clone a DNA segment in bacteria takes days.
- When the source of DNA is scanty or impure, it can be amplified by PCR technique.
- Amplification can make the identification of DNA easier.
- Since the sequence of HIV DNA is known, its amplification by PCR can help detect HIV DNA in blood or tissue samples.
- This is often the best way to detect infection.
- DNA from single embryonic cell is amplified by PCR for rapid prenatal diagnosis of genetic disorders.
- DNA from tiny amounts of blood, tissue or semen found at the site of crime can be amplified to facilitate its iden tification.
- DNA technology can help identify individuals with genetic disorders before the appearance of symptoms, even before birth.
- It is also possible to identify symptomless carriers of potentially harmful recessive alleles, such as of haemophilia, phenylketonurea (PKU).
- PCR is also helpful in DNA fingerprinting.
- Vitamin B2 ( Riboflavin )
- Riboflavin is produced commercially by direct fermenta tion utilizing the fungus Ashbya gossypii.
- Fermentation conditions -pH 6.0 to 7.5.4 to 5 days at 28-30 ° C, aerobic.
- Vitamin B12 ( Cobalamine )
- Now a days vitamin B12 is produced by a direct fermentation utilizing bacteria such as Propionibacterium shermanii, P. frendenreichii and Pseudomonas denitrificans.
- Fermentation conditions -pH 6 to 7.7 . 2 days at 26-28 ° C. aerobic
- Vitamin C ( Ascorbic Acid )
- Vitamin C was first recognized when in 1747, Scottish naval surgeon James Lind discovered that something in Citrus foods prevented scurvy.
- In 1928 Albert Szent - Gyorgyi, a much admired biochemist, was the first to isolate vitamin C ( ascorbic acid ).
- He later won the 1937 Nobel Prize in Physiology and Medicine for other work.
- Vitamin C was the first vitamin to be synthesized artificially in a process invented by Dr. Tadeusz Reichstein, of the Swiss Institute of Technology in Zurich in 1939.
- Vitamin C is produced by utilizing Gluconobacter oxydans.
- Fermentation conditions -pH 7, 45 hours at 30 ° C, aerobic.
- Vitamin A ( B - Carotene )
- B - carotene is produced by members of choanephoraceae family of phycomycetes . Phycomyces blakesleeanus, Choanephora cucurbitarum and Blackeslea trispora have been extensively studied for their ability to produce B - carotene.
Making a Choice of Baby's Sex
- Recently techniques have also been developed which will not require preferential abor tion but will allow preferential fertilization by male (carrying Y chromosome) or female (carrying X chromosome) determining sperms.
- There are techniques available now, which allow separation of sperms carrying Y chromosomes, from the ejaculate of a man ( through Ericson's method developed by R. Ericson of U.S.A ) to be used for insemination of ovulating women.
- This technique (using quinacrine stain) has been used with 80 % success in 47 sperm centres in the world including one in Mumbai.
- Ericson has actually established a company named Gametrics Ltd, in California , U.S.A. which specializes in separating sperms with Y chromosome and hundreds of male children have been produced with its help.
- Techniques have also been developed to separate sperms carrying X chromosome for artificial insemination leading to the birth of female children.
- This technique involves ' sephadex gel column ' in which sperms with Y, being lighter are trapped in gel and those with X being heavier reach the bottom of the column, and can be used for inseminaton.
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