Question 1:
Crystals of Bt toxin produced by some bacteria do not kill the bacteria themselves because:
Answer:
toxin is inactive
Question 2:
What are transgenic bacteria? Illustrate using any one example.
Answer:
Those bacteria whose DNA is manipulated to possess and express an extra (foreign) gene are
known as transgenic bacteria.
Example. Human Growth hormone production by transgenic Escherichia coli.
1. The pituitary gland of humans produces growth hormones that regulate the growth and
development.
2. However, in children stunted growth occurs due to deficiency of the hormone which is
called pituitary dwarfism.
3. For this, the hGH is now available as recombinant protein.
4. The hGH-coding DNA sequence is linked with the bacterial signal sequence of E.coli.
5. The hGH is secreted into the periplasmic space of bacterial cell by the signal peptides
wherefrom the protein is purified.
Question 3:
Compare and contrast the advantages and disadvantages of production of genetically modified crops.
Answer:
The advantages of production of genetically modified crops are:
1. They have proved to be extremely valuable tools in studies on plant molecular biology,
regulation of gene action, identification of regulatory / promotory sequences.
2. Genetically modified crops have improved agronomic and other features such as resistance
to biotic and abiotic stresses.
3. Over ripening losses can be reduced e.g., flavr savr tomato.
4. Nutritional values are improved e.g., Golden rice has high vitamin A content.
5. Viral resistance can be introduced.
6. Number of pharmaceuticals like insulin, interferon, blood clotting factors be
improved.
7. Insect resistance can be introduced e.g. cry gene can be introduced into cotton, wheat
and rice form Bacillus thuringiensis.
The main disadvantages of production of
genetically modified crops are:
1. Many transgenes are expressed at low levels which usually limit their usefulness.
2. Sometimes, the expression of transgenes is suppressed in transgenic plants, this is
called gene silencing.
3. The undesirable features are also carried along with desirable features in transgenic
plants such as necrosis, reduced growth, sterility, etc.
4. Genetic pollution can be there.
5. Weeds also become resistant.
6. Bt cotton, Bt wheat also destroy pollinators and disseminators.
7. Product of transgene may be allergic or toxic.
Question 4:
What are Cry proteins? Name an organism that produces it. How has man exploited this protein to his benefit?
Answer:
1. Cry proteins are also called as crystal proteins.
2. They are produced by Bacillus thuringienesis and forms crystalline inclusions in the
bacterial spores. The molecular weight ranges from 70–136 KDa and are present in inactive
form in bacteria.
3. Cry proteins possess the insecticidal activities against Lepidopteran, Dipteran and
Coleopteran insects.
4. They have been useful in protection of crops of cotton, corn, tomato etc.
Question 5:
What is gene therapy? Illustrate using the example of adenosine deaminase (ADA) deficiency.
Answer:
Gene Therapy. It is defined as the introduction of a normal functional gene into cells which
contain the defective allele of concerned gene with the objective of correcting a genetic
disorder or an acquired disorder.
Treatment of ADA deficiency.
1. Gene therapy was used to correct the genetic disorder called Severe Combined Immuno
Deficiency (SCID) syndrome produced by adenosine deaminase (ADA) deficiency.
2. In this, Normal ADA gene copies were produced by cloning.
3. Packed into defective retrovirus, most of the viral genes were replaced by ADA gene.
4. Lymphocytes were isolated from the patients.
5. Recombinant DNA of the recombinant retroviruses were used to infect the lymphocytes.
6. The infected cells expressing the ADA gene were injected back into the patients.
7. The normal ADA gene was then expressed in the patients and ADA deficiency is partially
corrected. If the gene isolated from bonemarrous cells producing ADO is introduced into
embryonic cells at early stages,
it could provides permanent cure.
Question 6:
Why is the introduction of genetically engineering hymphocyte into a ADA deficiency patient not a permanent cure? Suggest a possible permanent cure.
Answer:
Gene Therapy. It is defined as the introduction of a normal functional gene into cells which
contain the defective allele of concerned gene with the objective of correcting a genetic
disorder or an acquired disorder.
Treatment of ADA deficiency. 1. Gene therapy was used to correct the genetic disorder called
Severe Combined Immuno Deficiency (SCID) syndrome produced by adenosine deaminase (ADA)
deficiency.
2. In this, Normal ADA gene copies were produced by cloning.
3. Packed into defective retrovirus, most of the viral genes were replaced by ADA gene.
4. Lymphocytes were isolated from the patients.
5. Recombinant DNA of the recombinant retroviruses were used to infect the lymphocytes.
6. The infected cells expressing the ADA gene were injected back into the patients.
7. The normal ADA gene was then expressed in the patients and ADA deficiency is partially
corrected. If the gene isolated from bonemarrous cells producing ADO is introduced into
embryonic cells at early stages,
it could provides permanent cure.
Question 7:
Can you suggest a method to remove oil (hydrocarbon) from seeds based on your understanding of DNA technology and Chemistry of oil.
Answer:
The genes for the formation of oil in the seed should be identified. The specific gene can be removed by using an enzyme restriction endonucleases. Such DNA molecule should be treated with DNA ligases to seal at the broken ends. These cells when grown in a minimum nutrient medium, under aseptic conditions will differentiate into a new lant whose seeds will not have oil in them.
Question 8:
Find out from internet what is Golden Rice?
Answer:
Golden Rice. It is genetically engineered rice rich in Vitamin A. It was prepared in introducing three genes involved in biosynthetic pathway for carotenoid, the precursor of vitamin A. The colour of golden rice is yellow due to synthesis of provitamin A in entire grain.
Question 9:
Does our blood have proteases and nucleases?
Answer:
No, blood does not have proteases and nucleases.