Biology 5 Marks Questions

Insulin used for diabetes was earlier extracted from pancreas of slaughtered cattle and pigs. Insulin from an animal source, though caused some patients to develop allergy or other types of reactions to the foreign protein. Insulin consists of two short polypeptide chains: chain A and chain B, that are linked together by disulphide bridges. In mammals, including humans, insulin is synthesised as a pro-hormone (like a pro-enzyme, the pro-hormone also needs to be processed before it becomes a fully mature and functional hormone) which contains an extra stretch called the C peptide. This C peptide is not present in the mature insulin and is removed during maturation into insulin. The main challenge for production of insulin using rDNA techniques was getting insulin assembled into a mature form. In 1983, Eli Lilly an American company prepared two DNA sequences corresponding to A and B, chains of human insulin and introduced them in plasmids of E. coli to produce insulin chains. Chains A and B were produced separately, extracted and combined by creating disulfide bonds to form human insulin.

The production of genetically modified (GM) or transgenic plants has several advantages.

1. Most of the genetically modified crops have been developed for pest resistance, which increases the crop productivity and reduces the reliance on chemical pesticides.
2. Many varieties of genetically modified food crops have been developed, which has good nutritional quality. For example, golden rice is a transgenic variety in rice, which is rich in vitamin A.
3. These plants prevent the loss of fertility of soil by increasing the efficiency of mineral usage.
4. They are highly resistant to unfavourable abiotic conditions.
5. The use of genitically modified crops decreases the post harvesting loss of crops.

But, there are certain controversies regarding the use of genetically modified crops around the world. The use of these crops can affect the native biodiversity in an area. For example, the use of Bt toxin to decrease the amount of pesticide is posing a threat for beneficial insect pollinators such as honey bee. If the gene expressed for Bt toxin gets expressed in the pollen, then the honey bee might be affected. As a result, the process of pollination by honey bees would be affected. Also, genetically modified crops are affecting human health. They supply allergens and certain antibiotic resistance markers in the body. Also, they can cause genetic pollution in the wild relatives of the crop plants. Hence, it is affecting our natural environment.

1. (d) All of these.

2. (c) Mammary glands.

3. (a) Both (A) and (C)

Explanation:

Mouse has short gestation period and it produces several number of offspring per pregnancy.

4. (d) All of these.

5. (a) Both assertion and reason are true and reason is the correct explanation of assertion.

1.  

Proinsulin	Mature Insulin
It has A, B and C polypeptide strands.	It has only A and B polypeptide strands.
It is non functional.	It is functional.

2. Two DNA sequences corresponding to its A and B chains were prepared, and were introduced in plasmids of E. coli, to produce insulin chains, chains A and B were produced separately, extracted, and combined by creating disulphide bonds.
3. Because it does not develop allergy or other type of reactions which was developed by the use of insulin used earlier.

Biopesticides: An application of biotechnology in agriculture is the production of pest-resistant plants which could decrease the amount of pesticides being used. Bt toxin is produced by a bacterium c led Bacillus thuringiensis. Bt toxin gene has been cloned from the bacteria and been expressed in plants ro provide resistance to the insects without the need for insecticides and so named as biopesticide, e.g. Br cotton, Bt corn, rice, tomato, potato and soybean, etc.

Pest resistant plants:

• A nematode Meloidegyne incognitia infects the roots of tobacco plants which reduces the production of tobacco.
• It can be prevented by using RNA interference (RNAi) process which is checked by silencing of specific mRNA due to a complementary dsRNA.
• dsRNA binds and prevents translation of the mRNA (silencing).
• By using Agrobacterium vectors, nematode-specific genes were introduced into the host plants which produce both sense and anti-sense RNA in the host cells.
• These two RNAs are complementary to each other and form a double-stranded RNA (dsRNA) that initiates RNAi and hence silence the specific mRNA of the nematode.
• The parasite cannot survive in the transgenic host, so protects the plants from pests.

1. Natural predation/biological control.

Examples - lady bird used to kill aphids// dragon flies used to kill mosquitoes// Bacillus thuringiensis used to kill cotton bollworm/caterpillar/butterfly caterpillar.

2.  

S.No.	Conventional Pest Control	Organic farming based pest control
1.	Use of chemical insecticides & pesticides.	No chemical used.
2.	Harmful to non-target organisms.	Not harmful to non-target organisms.
3.	Cause environmental pollution.	No adverse impact on environment.

1. Sakshi's father explained the harmful effects of agrochemicals on the health, environment and the fields.
2. Agrochemical is a term used to refer to the various chemical products used in agriculture such as fertilisers, pesticides and herbicides.
3. Biofertilisers or biopesticides are preferred because they are cost effective, environment friendly and provide better nourishment to plants.
4. Health awareness, eco-friendly nature, careful and vigilant attitude.

Gene expression can be controlled with the help of RNA interference (RNAi). RNAi takes place in all eukaryotic organisms and is part of the cellular defense. Under this method, a complementary dsRNA binds to and prevents translation of mRNA (silencing) and thus silences a specific mRNA. Thus gene expression which could have been carried out by the mRNA does not happen.
This method has been used to encounter a nematode in plants. Agrobacterium is used as vector to introduce nematode specific gene into the host plant. The introduction of DNA results in production of sense and anti-sense RNA in the host cells. These two RNAs form dsRNA and silence the specific mRNA.

1. E. coli.
2. Eli Lilly (an American company).
3. Diabetes.
4. The doctor is responsible, caring and honest towards his duty.

1. Reduce usage of chemical pesticides: Bt toxin is produced by a bacterium called Bacillus thuringiensis (Bt for short). Bt toxin gene has been cloned from the bacteria and been expressed in plants to provide resistance to insects without the need for insecticides; in effect created a bio-pesticide. Examples are Bt cotton, Bt com, rice, tomato, potato and soyabean etc.
2. Enhance nutritional value of food crops: Golden rice is the transgenic variety of basmati rice which gives high yield and rich in vitamin A, so it is used in the deficiency of vitamin-A causing night blindness and skin disorder.

GM plants have been useful in many ways. Genetic modification has:

1. Made crops more tolerant to abiotic stresses (cold, drought, salt, heat).
2. Reduced reliance on chemical pesticides (pest-resistant crops).
3. Helped to reduce post-harvest losses.
4. Increased efficiency of mineral usage by plants (this prevents early exhaustion of fertility of soil).
5. Enhanced nutritional value of food>e.g., Vitamin ‘A’ enriched rice.

In addition to these uses, GM has been used to create tailor-made plants to supply alternative resources to industries, in the form of starches, fuels and pharmaceuticals.

S. No	Column A	S. No	Column B
(i)	Eli Lilly	(a)	Humulin
(ii)	Pest resistance	(b)	Bt cotton
(iii)	Crylab	(c)	Corn borer
(iv)	CryIAC	(d)	Cotton bollworm
(v)	RNAi	(e)	Meloidegyne incognitia
(vi)	Vitamin A	(f)	Golden Rice

1. (a) Transfer DNA.

Explanation:

Transfer DNA (T-DNA) is the transferred DNA of Ti plasmid of some species of bacteria.

2. (b) Maize.

Explanation:

Agrobacteriurn infects all broad-leaved agricultural crops. It does not infect cereals.

3. (a) Integrated into the target host genome.

Explanation:

Part of Ti plasmid transferred into the plant cell DNA, is called T-DNA. This T-DNA with desired DNA spliced into it, is inserted into the chromosomes of the host plant where it produces copies of itself, by migrating from one chromosomal position to another at random. But it no longer produces tumors.

4. (d) All of these.

5. (a) Both assertion and reason are true and reason is the correct explanation of assertion.

Bt toxin gene is isolated from Bacillus thuringiensis, this gene is incorporated in the cotton plant, using a vector, the plant is now a Bt cotton and it produces crystals of protoxin, which is an insecticidal protein, when the insect ball worm infects the cotton plant the toxin is taken in, pH of the gut solubilizes these crystals, converts it into active form which binds to the epithelial cells of the gut, causes swelling, leads to lysis and results in death of insect.

1. (d) Somatic cell gene therapy to replace one ADA gene copy in bone marrow lymphoblasts.

Explanation:

Viral delivery using adenoviruses and retroviruses are specific and ensure effectiveness. The viral vector recognises and bind to receptor on cell and enters cells. The vector is able to deliver genes to specific target tissues and is able to deliver DNA to the nucleus.

2. (b) DNA attached to a ligand.

Explanation:

Viral delivery using adenoviruses and retroviruses are specific and ensure effectiveness. The viral vector recognises and bind to receptor on cell and enters cells. The vector is able to deliver genes to specific target tissues and is able to deliver DNA to the nucleus.

3. (d) Receptor molecules.

Explanation:

The liposome's glycolipid membrane containing specific carbohydrates recognises and binds to receptor molecules on cell surface membrane of target cells. The liposome is thus able to deliver genes to specific target cells and is able to deliver DNA into the cell.

4. (d) Type II diabetes.

Explanation:

Type II diabetes is a type of multifactorial and polygenic (complex) disorder where manifestation of disease may be dependent on the effects of multiple genes in combination with lifestyle and environmental factors.

5. (b) II, IV and V only

A biological agent which works as pesticide is called bio pesticide.
Bio pesticides can be of following types:

• Microbial: Many Bacteria and fungi have pesticidal properties.
• Herbal: Some plants; like neem and canola can help in controlling pesticides.
• Plant Incorporated Protectants: These are incorporated into the genes of a plant through genetic engineering. Bt cotton is an example of plant with incorporated pesticidal property. Bacillus thuringiensis affects the pests of Lepidoptera, Coleoptera and Diptera. It is a well-known example of microbial pesticide. A gene in B. thuringiensis produces a toxin which remains inactive in the bacterium. Once this toxin enters the gut of the pest; the alkaline pH makes it active. The toxin results in perforations in the gut of the pest and eventually the pest is killed. This gene has been incorporated in Bt cotton, Bt tomato, Bt brinjal, etc. These GM crops are giving good results.

1. (c) Polypeptide chain C.

Explanation:

A represents polypeptide chain Cwhich is removed prior to insulin formation.

2. (d) 5, 3, 4, 1, 2

3. (d) Sticky ends in the cut plasmid and insulin gene are complementary.

Explanation:

Each particular restriction enzyme produces unique sticky ends. Using the same enzyme for both the bacterial and human DNA will produce complementary sticky ends that can bind together by complementary base pairing. This would allow the human insulin gene to be inserted into the plasmid.

4. (a) It provides optimal conditions for the transgenic to multiply rapidly.

Explanation:

The optimal temperature, pH, oxygen and nutrient conditions in the fermenter allow the bacteria containing the insulin gene to reproduce quickly and produce large quantities of it.

5. (c) The resulting E.coli bacteria do not contain the human insulin gene.

Explanation:

DNA ligase forms strong hydrogen bonds between the DNA bases on the human insulin gene and the bacterial plasmid, producing a continuous double stranded DNA loop. Without DNA ligase, the human insulin gene, despite being able to undergo complementary base pairing with the bacterial DNA at the sticky ends would not be securely inserted into the plasmid. Thus, the resulting E.coli bacteria would receive plasmids that lack the human insulin gene.

1. (c) Tiley can divide and be made to differentiate into various types of cell.

Explanation:

Stem cells are capable of dividing indefinitely and producing copies of themselves. In addition, stem cells can undergo differentiation giving rise to specialized cell types.

2. (a) Adult stem cells.

Explanation:

Adult stem cells are tissue specific and can enter normal differentiation pathways to form only the specialized cell types of the tissue which they reside in.

3. (b) They can differentiate into any cellular component of blood.

Explanation:

Umbilical cord blood stem cells are multipotent in that they have the ability to differentiate into limited cell types to give rise to a range of specialized cells that have a specific function. Umbilical cord stem cells found in blood only can differentiate into any cellular component of blood, e.g., white blood cells (such as B lymphocytes, T lymphocytes, natural killer cells, macrophages and platelets etc.) vital for fighting infections and safeguarding the body, red blood cells - important for transporting oxygen to cells.

4. (d) A proper stem-cell niche.

Explanation:

Stem cell niche is used to describe the microenvironment in which stem cells are found. Since fertility was restored after the injection of spermatogonia, it suggests that spermatogonium displays the general properties of stem cells such as being capable of dividing indefinitely and producing copies of themselves (self-renewal), can undergo differentiation giving rise to specialised cell types (haploid sperm). As fertility was not restored upon injection of secondary spermatocytes, it suggest that the secondary spermatocytes do not have a stem cell niche and do not display the properties of stem cell.

5. (c) ESCs are pluripotent.

Explanation:

Embryonic stem cells are pluripotent cells. That is, they have the ability to develop into almost any kind of cell in the body (as seen from diagram, hematopoietic SCs, neural SCs and mesenchymal SCs) except extra-embryonic membrane (but not the trophoblast).

1. Biopesticides: Biological agents/micro organisms that are used for control of weeds, insects and pathogens

Examples:

The bacterium Bacillus thuringiensis, was the first biopesticide to be used on a commercial scale in the world. Spores of this bacterium produce the insecticidal Cry protein. So spores of this bacterium kill larvae of certain insects.

The microorganisms used as biopesticides include viruses, bacteria, fungi, protozoa and mites.

2. Mycorrhiza: Symbiotic association between the fungus and the roots of higher plants.

These fungi solubilise phosphorus/produce plant growth promoting substances/protect host plants from soil pathogens.

1. Thermus aquaticus: It is a themostable DNA polymerase, does not denatured and remain active during PCR.
2. Adenosine deaminase, this enzyme is essential for immune system to function, its deficiency can be cured by gene therapy, lymphocytes from the patients are extracted and cultured, functional ADA cDNA are introduced into lymphocyte using a vector, lymphocytes are returned to the patient.

Animals that have had their DNA manipulated to possess and express an extra (foreign) gene are known as transgenic animals, e.g. transgenic rats, rabbits, pigs, sheep, cows and fishes. Over 95% of all the existing transgenic animals are mice.
There are several benefits of transgenic animals:

1. Normal physiology and development: Transgenic animals can be specifically designed to allow the study of how genes are regulated and how they affect the normal functioning of the body and its development. For example, the study of complex factors involved in growth such as insulin like growth factors.
2. Study of disease: Many transgenic animals are designed to increase the understanding of how genes contribute to the development of diseases such as cancer, cystic fibrosis, rheumatoid arthritis and Alzheimer's. These are specially made to serve as models for human diseases, so that investigation of new treatments for diseases is made possible.
3. Biological products: Human diseases can be treated by medicines that contain biological products:

1. Transgenic animals that produce useful biological products can be created by the introduction of the portion of the DNA or genes that code for a particular product such as human protein (a-1 antitrypsin) which is used to treat emphysema.
2. Similar attempts are being made for the treatment of Phenylketonuria (PKU) and cystic fibrosis. For example, the first transgenic cow Rosie produced human protein enriched milk (2.4 g/L) in 1997. The milk contained the human alpha lactalbumin and was nutritionally a more balanced product for human babies than natural cow's milk.

4. Vaccine safety: Transgenic mice are being used for testing the safety of vaccines before they are used on humans, e.g. polio vaccine. If found reliable and successful they could replace the use of monkeys in order to test the safety of batches of the vaccine.

Transgenic animals are the products of genetic engineering and express specific gene(s) from totally unrelated source. Following are the four main areas where they can be utilised:

1. To study normal physiology and development these animals can be used to study as to which factor/ gene products are needed at what time of development. By expression of certain genes, they help scientists to understand the normal gene expression at various stages of growth and development.
2. Study of Diseases: Transgenic animals can be created to serve as models for various human diseases. They also help us understand the involvement of various genes in diseases like cancer, Parkinson’s disease etc.
3. Vaccine safety: Transgenic animals can be used to test vaccines like polio vaccine. Transgenic mice have shown promising results in this area and would replace the vaccine testing on monkeys in the years to come.
4. Chemical safety testing: Transgenic animals are created which are more sensitive to certain chemicals/ drugs. These are used to study the toxicity or side effects of that chemical/ drug. The advantage is that we get results faster.

1. (b) Insect resistant.

Explanation:

The genetically modified crop called Bt cotton contains Bt toxin genes. The gene cry I Ac and cry II Ab control cotton bollworms. Similarly, cry I Ab has been introduced in Bt corn to protect the same from corn borer.

2. (d) Both (a) and (c).

Explanation:

cry I Ab has been introduced to Bt corn to protect them from corn borer. cry I Ac and cry II Ab control cotton bollworms.

3. (d) GM plants can cause gene transfer to non-target plant species.

Explanation:

Gene transfer to non-target plant species is a major disadvantageous concern of GM plants. lt can even cause to produce 'superweeds'

4. (b)Soil borne bacteria.

5. Both assertion and reason are true and reason is the correct explanation of assertion.

Explanation:

The Bt toxin proteins exist as inactive protoxins but once an insect ingests the inactive toxin it is converted into an active form of toxin due to the alkaline pH of the alimentary canal that solublises the crystals. The activated toxin binds to the surface of midgut epithelial cells and create pores which cause cell swelling and lysis and foully cause death of the insect.