7.7 Execise Problems

Q1. What are the various public health measures, which you would suggest as safeguard against infectious diseases?

Answer: Health measures as a safeguard against infectious diseases.
The public health measures that can be taken to avoid infection of diseases are as follows:
(a) Vaccination – The populations should be vaccinated timely and properly so that they don’t develop diseases. For diseases like cholera, TB, hepatitis vaccination are available
(b) Education and awareness – Everybody should be educated or made aware of the infectious diseases so that they can protected themselves from infectious diseases
(c) Sanitation – Adopting public sanitation measures is good for avoiding infectious diseases. We should maintain cleanliness in our surroundings. One should also maintain cleanliness and consume only clean drinking water and contamination-free fruits and vegetables.
(d) Eradication – The vectors of diseases must be eradicated by destroying the breeding sites of many vectors.

Q2. In which way has the study of biology helped us to control infectious diseases?

Answer: Biological research and tools have always been helpful in controlling and eradicating infectious or communicable diseases. biology helps us in various ways, some of them are:
(a) By using the knowledge of biology we can know the nature of the diseases.
(b) To find out the mode of transmission of disease, biology plays a very important role, for example, if a person shows symptoms like vomiting or diarrhea, the mode of transmission can be through contaminated food. and disease will take the -faecal route.
(c) To provide treatment and cure the infected person by medicines.
(d) Provide vaccines and immunization treatment for preventing further spread of disease.

Q3. How does the transmission of each of the following diseases take place?
(a) Amoebiasis (b) Malaria (c) Ascariasis (d) Pneumonia

Answer: (a) Amoebiasis-  It transmits via consumption of water and food contaminated by amoebic cysts.
(b) Malaria- It transmits from one person to another by means of female Anopheles mosquito. When this mosquito bites a diseased person, along with blood it takes the parasite and while biting a healthy person, the parasite transfers to the healthy person.
(c) Ascariasis – It transmits through food and water contaminated with eggs of the parasite.
(d) Pneumonia – It transmits through droplet infection i.e. through sneeze ,cough, sharing utensils etc.

Q4. What measure would you take to prevent water-borne diseases?

Answer: Drinking contaminated water is one of the main reasons for water borne diseases such as typhoid, cholera etc. The measures that can be taken to prevent water-borne diseases are as follows
(a) To prevent these diseases we would dispose of sewage, excreta, etc. properly
(b) We should check our water reservoirs regularly.
(c) We should consume clean, pure, contamination free water only.

Q5. Discuss with your teacher what ‘a suitable gene’ means, in the context of DNA vaccines.

Answer: A suitable gene means that special DNA segment which can be injected into the host body to produce specific proteins. These specific proteins should be such that they can kill the particular disease-causing organism present in the host body.

Q6. Name the primary and secondary lymphoid organs.

Answer: Lymphoid organs are the organs in which origin, maturation and proliferation of lymphocytes occur. Lymphoid organs are of two types i.e.primary lymphoid organs and secondary lymphoid organs. In primary lymphoid organs, the origin of lymphocytes occurs. These include bone marrow and thymus. After maturation, lymphocytes migrate to a secondary lymphoid organ-like spleen, lymph nodes, tonsils, peyer’s patches of small intestine and appendix. They provide the sites for interaction of lymphocytes with antigens.

Q7. Expand well-known abbreviations
(a) MALT (b) CMI (c) AIDS (d) NACO (e) HIV

Answer:
(a) MALT- Mucosal Associated Lymphoid Tissue
(b) CMI – Cell Mediated Immunity
(c) AIDS – Acquired Immunodeficiency Syndrome
(d) NACO – National AIDS Control Organisation
(e) HIV – Human Immunodeficiency Virus

Q8. Differentiate the following and give examples of each :
(a) Innate and acquired immunity (b) Active and passive immunity

Answer: (a) Innate and acquired immunity

\(
\begin{array}{|l|l|}
\hline \text { Innate immunity } & \text { Acquired immunity } \\
\hline \begin{array}{l}
\text { It is a non-specific type of defence present at } \\
\text { the time of birth and provides different kinds } \\
\text { of barriers to the entry of foreign agents into } \\
\text { the body. }
\end{array} & \begin{array}{l}
\text { It is pathogen specific } \\
\text { defence characterised } \\
\text { by memory. }
\end{array} \\
\hline \text { It remains throughout the life } & \text { It is short-lived } \\
\hline \text { Innate immunity is inheritable } & \text { Acquired immunity is not inheritable } \\
\hline
\end{array}
\)

(b) Active and passive immunity

\(
\begin{array}{|l|l|}
\hline \text { Active immunity } & \text { Passive immunity } \\
\hline \begin{array}{l}
\text { Active immunity develops in a } \\
\text { person’s own body in } \\
\text { response to an infection or any } \\
\text { disease }
\end{array} & \begin{array}{l}
\text { Passive immunity develops a } \\
\text { person’s body when antibodies } \\
\text { from outside are injected into } \\
\text { the body }
\end{array} \\
\hline \begin{array}{l}
\text { Active immunity does not have side } \\
\text { effects }
\end{array} & \text { It may have side effects } \\
\hline \text { It is long lasting } & \text { It has a short span } \\
\hline \begin{array}{l}
\text { Active immunity takes a long } \\
\text { period to provide show effect }
\end{array} & \begin{array}{l}
\text { Passive immunity immediately } \\
\text { show effects and provides relief. }
\end{array} \\
\hline
\end{array}
\)

Q9. Draw a well-labelled diagram of an antibody molecule.

Answer: The well-labelled diagram of an antibody molecule is as follows

Q10. What are the various routes by which transmission of human immunodeficiency virus takes place?

Answer: Acquired immunodeficiency syndrome is caused by the human immunodeficiency virus. The various routes by which transmission of human immunodeficiency virus takes place are:
(a) Through sharing of infected needles.
(b) Having sex with an infected person without using condoms.
(c) Infected mother to baby through the placenta.
(d) Through the transfer of blood from an infected person to normal person

Q11. What is the mechanism by which the AIDS virus causes deficiency in the immune system of the infected person?

Answer: AIDS is a viral disease caused by the HIV virus. It is considered to be one of the most dangerous diseases with no cure until now. HIV affects the immune system of the body and makes it unable to perform its usual functions. The mechanism by which HIV virus causes deficiency of the immune system is as follows:
(a) After entering into the system, HIV binds itself to the surface receptors present on helper T-cells and introduces its RNA and reverse transcriptase enzyme into these cells.
(b) After this, by utilizing the host cell’s machinery, HIV produces a copy of DNA itself through reverse transcription.
(c) This copy of DNA gets incorporated into the genome of the host cell. This is called the provirus form, which directs the viral genome to produce new virus particles.
(d) The subsequent formation and release of viral particles destroy the host cell. As a result, the number of T helper cells decreases.
(e) AIDS occurs when the count of helper T-cells falls very much and the body is unable to fight against diseases.

Q12. How are cancerous cells different from a normal cell?

Answer: Differences between cancerous cells and normal cells :

\(
\begin{array}{|l|l|}
\hline \text { Cancer cells } & \text { Normal cells } \\
\hline \begin{array}{l}
\text { Cancerous cells divide at a faster rate forming a } \\
\text { mass of cells called tumour. }
\end{array} & \begin{array}{l}
\text { Normal cells divide at a normal rate and do not } \\
\text { cause the formation of tumors }
\end{array} \\
\hline \begin{array}{l}
\text { They spread, move to another tissue } \\
\text { and affects their normal functions. } \\
\text { Thus, they are not restricted to one } \\
\text { location. }
\end{array} & \text { These are restricted to one location. } \\
\hline
\end{array}
\)

Q13. Explain what is meant by metastasis.

Answer: Metastasis – It refers to the process of formation of secondary tumors from the fragments of primary tumors. The pieces Primary tumors are carried to neighbouring tissues via blood. Metastasis is the last stage of cancer.

Q14. List the harmful effects caused by alcohol/drug abuse.

Answer: Harmful effects caused by alcohol/drug abuse.
(a) These reduce the efficiency of all the tissues of our body. Long time use of drugs and alcohol can cause many mental and physical diseases.
(b) These dilate the blood vessels and affect the normal functioning of the heart.
(c) Excessive drug/alcohol abuse can lead to cirrhosis in the liver.
(d) Excessive drug/alcohol abuse may increase the workload of kidneys and cause kidney failure.
(e )Long time use of alcohol/drugs can cause impotence.
(f) Alcoholics lose their image in society because of their nature created under the influence of alcohol.
(g) Drug/alcohol abuse increases family violence which affects their family and social life.

Q15. Do you think that friends can influence one to take alcohol/drugs? If yes, how may one protect himself/herself from such an influence?

Answer: Yes, friends can influence one to take alcohol/drugs. However, we can avoid those conditions in the following ways:
(a) We should avoid the company of those friends who take drugs or alcohol.
(b) We should increase our willpower to stay away from these things.
(c) We should have knowledge about the bad results of taking alcohol or drugs.
(d) We should take the help of our parents if any question arises in our mind regarding this.
(e) We should immediately consult a doctor if any symptoms like depression or frustration are felt.

Q16. Why is that once a person starts taking alcohol or drugs, it is difficult to get rid of this habit. Discuss it with your teacher.

Answer: Once a person starts taking alcohol or drugs, it becomes very difficult to get rid of this habit. It is mainly because according to this person, alcohol is the only way to attain a normal state. Alcohol does not affect any organ other than the nervous system of a human body. However, due to the effect on the nervous system other organs also get affected. Prolonged use of alcohol can make a person so addicted that his nervous system works normally only in the presence of alcohol or drugs. Even when someone starts withdrawing alcohol or drugs, the body gets affected badly and withdrawal symptoms are seen. Due to these withdrawal symptoms, people often do not get rid of alcohol.

Q17. In your view what motivates youngsters to take to alcohol or drugs and how can this be avoided?

Answer: There are several reasons which motivate youngsters to take alcohol. Some of these are given here under:
(a) Appreciation from friends on the use of such things.
(b) Sometimes youngsters start taking these things just for pleasure
(c) To get rid of depression and frustration, youngsters often move to drugs/alcohol.
(d) After watching it in movies, adolescents think that taking alcohol or drugs is a sign of being cool and royal. So, they also start following these.
(e) Sometimes the company of wrong friends makes us alcoholic.
(f) We can avoid all these, by sharing our problems with our parents. We should understand the bad effects of alcohol and should not look at alcohol as a sign of royalty or greatness. There are many other ways to solve problems other than alcohol intake. Youngsters should be taught about moral values.

Exemplar Section

VERY SHORT ANSWER TYPE QUESTIONS

Q1. Certain pathogens are tissue/organ specific. Justify the statement with suitable examples.

Answer: Salmonella typhi causes typhoid and infects small intestine while intestinal endoparasite causes amoebic dysentery and infects large intestine.

Q2. The immune system of a person is suppressed. In the ELISA test, he
was found positive to a pathogen.
a. Name the disease the patient is suffering from.
b. What is the causative organism?
c. Which cells of body are affected by the pathogen?

Answer: a. Acquired Immuno Deficiency Syndrome (AIDS)
b. Human Immuno deficiency virus (HIV)
c. Helper T-lymphocytes \(\left(T_H\right.\) or \(\left.T_4\right)\)

Q3. Where are B-cells and T-cells formed? How do they differ from each other?

Answer: Both B-cells and T-cells are formed in bone marrow. B-cells matures in bone marrow while T-cells matures in thymus. B-cells provides humoral immunity and T-cells provides cell mediated immunity (CMI).

Q4. Given below are the pairs of pathogens and the diseases caused by them. Which out of these is not a matching pair and why?
(a) Virus                 common cold
(b) Salmonella        typhoid
(c) Microsporum     filariasis
(d) Plasmodium       malaria

Answer: (c) Microsporum causes ringworm and not filariasis.

Q5. What would happen to immune system, if thymus gland is removed from the body of a person?

Answer: Thymus is the primary lymphoid organ. In thymus gland, immature lymphocytes differentiate into antigen-sensitive lymphocytes. If thymus gland is removed from the body of a person, his immune system becomes weak. As a result the person’s body becomes prone to infectious diseases,

Q6. Many microbial pathogens enter the gut of humans along with food. What are the preventive barriers to protect the body from such
pathogens? What type of immunity do you observe in this case?

Answer: (i) The mucus coating of the epithelium lining of the gut helps in trapping microbes entering the body.
(ii) Saliva in the mouth and hydrochloric acid in gastric juice secreted by stomach prevent microbial growth. This type of immunity is innate immunity.

Q7. Why is mother’s milk considered the most appropriate food for a new born infant?

Answer: Mother’s milk is considered as the most appropriate food for a new born infant because the yellowish fluid colostrum secreted by mother during the initial days of lactation has abundant antibodies (IgA) to protect the infant.

Q8. What are interferons? How do interferons check infection of new cells? 

Answer: Interferons are natural proteins produced by the cells of immune system in response to foreign agents such as viruses, tumor cells and parasites and protect non-infected cells from further infection. Interferons inhibit the viral replication within host cells, activate natural killer cells and macrophages, increases antigen presentation to lymphocytes, and induce the resistance of host cells to viral infection. When the antigen is presented to matching T-cells’ and B-cells, these cells multiply and remove the foreign substance.

Q9. In the figure, structure of an antibody molecule is shown. Name the parts A, B and C. Show A, B and C in the diagram.

Answer: A – Constant region of heavy chain
B – Constant region of light chain,
C – Variable region of light and heavy chain

Q10. If a regular dose of drug or alcohol is not provided to an addicted person, he shows some withdrawal symptoms. List any four such withdrawal symptoms.

Answer: The withdrawal symptoms are: a. Anxiety b. Shakiness c. Nausea d. Sweating

Q11. Why is it that during changing weather, one is advised to avoid closed, crowded and airconditioned places like cinema halls etc.?

Answer: During changing weather, one is advised to avoid closed, crowded and air- conditioned placed like cinema halls, etc., because during this period the infectious agents are more humerous and prevalent to which we are more vulnerable.

Q12. The harmful allele of sickle cell anemia has not been eliminated from human population. Such afflicted people derive some other benefit. Discuss.

Answer: The harmful alleles get eliminated from population over a period of time, yet sickle cell anaemia is persisting in human population because SCA is a harmful condition which is also a potential saviour from malaria. Those with the benign sickle trait possess a resistance to malarial infection. The pathogen that causes the disease spends part of its cycle in the red blood cells and triggers an abnormal drop in oxygen levels in the cell. In carriers, this drop is sufficient to trigger the full sickle-cell reaction, which leads to infected cells being rapidly removed from circulation and strongly limiting the infection’s progress. These individuals have a great resistance to infection and have a greater chance of surviving outbreaks. This resistance to infection is the main reason the SCA allele and SCA disease still exist. It is found in greatest frequency in populations where malaria was and is still often a serious problem.

Q13. Lymph nodes are secondary lymphoid organs. Explain the role of lymph nodes in our immune response.

Answer: Lymph nodes are small solid structures located at different points along the lymphatic system. Lymph nodes trap the microorganisms or other antigens, which happen to get into the lymph and tissue fluid. Antigens trapped in the lymph nodes are responsible for the activation of lymphocytes present there and cause the immune response.

Q14. Why is an antibody molecule represented as \(\mathrm{H}_2 \mathrm{~L}_2\)?

Answer: Each antibody molecule is made of the two heavy chains \(\left(\mathrm{H}_2\right)\) and two light chains \(\left(\mathrm{L}_2\right)\), hence represented as \(\mathrm{H}_2 \mathrm{~L}_2\).

Q15. What does the term `memory’ of the Immune system mean?

Answer: When body encounters a pathogen for the first time produce a response called \(1^{\circ}\) response. \(1^{\circ}\) response is of low intensity. When body encounters the same pathogen subsequently then body elicits \(2^{\circ}\) response. \(2^{\circ}\) response is highly intensified. This is due to the fact that our body have memory of the first encounter.

Q16. If a patient is advised Anti Retroviral Therapy, which infection is he suffering from? Name the causative organism.

Answer: The patient is suffering from AIDS. The causative organism for AIDS is HIV (Human Immuno deficiency Virus).

SHORT ANSWER TYPE QUESTIONS

Q1. Differentiate between active immunity and passive immunity.

Answer:

\(
\begin{array}{|l|l|}
\hline \text { Active immunity } & \text { Passive immunity } \\
\hline \text { (1) It develops in response to vaccine or infection. } & \begin{array}{l}
\text { It develops when readymade antibodies are } \\
\text { injected from outside. }
\end{array} \\
\hline \text { (2) It is long lasting. } & \text { It lasts for short period only. } \\
\hline \text { (3) Antibodies are produced within the body. } & \text { Antibodies are injected from outside. } \\
\hline \text { (4) It has no side effects. } & \text { It may cause reaction. } \\
\hline \text { (5) Immunity is not immediate. A time lapse occurs } \\
\text { for its development. } & \text { Immunity develops immediately } \\
\hline
\end{array}
\)

Q2. Differentiate between benign tumor and malignant tumor.

Answer:

• Benign tumors normally remain confined to their original location and do not spread to other parts of the body and cause little damage.
• Malignant tumors are a mass of proliferating cells called neoplastic or tumor cells. Neoplastic cells grow very rapidly, invading and damaging the surrounding normal tissues. As these cells actively divide and grow they also starve the normal cells by competing for vital nutrients.
• Cells sloughed from such tumors reach distant sites through blood, and wherever they get lodged in the body, they start a new tumor there. This property called metastasis is the most feared property of malignant tumors.

Q3. Do you consider passive smoking is more dangerous than active smoking? Why?

Answer: Yes, passive smoking is also dangerous as the active smoking because the person is exposed to the same harmful effects of smoking like emphysema, bronchitis, lung cancer, urinary bladder cancer or even peptic ulcer.

Q4. “Prevention is better than cure”. Comment.

Answer: Prevention is better than cure is true as in same cases the disease is non- curable like AIDS and Hepatitis-B, and in some cases’ the treatment causes financial problems in the family.

Q5. Explain any three preventive measures to control microbial infections.

Answer: (i) Maintenance of personal and public hygiene is very important for prevention and control of many infectious diseases. Measures for personal hygiene include keeping the body clean; consumption of clean drinking water, food, vegetables, fruits, etc. Public hygiene includes proper disposal of waste and excreta; periodic cleaning and disinfection of water reservoirs, pools, cesspools and tanks and observing standard practices of hygiene in public catering.
(ii) In cases of air-borne diseases such as pneumonia and common cold, in addition to the above measures, close contact with the infected persons or their belongings should be avoided.
(iii) For diseases such as malaria and filariasis that are transmitted through insect vectors, the most important measure is to control or eliminate the vectors and their breeding places. This can be achieved by avoiding stagnation of water in and around residential areas, regular cleaning of household coolers, use of mosquito nets, introducing fishes like Gambusia in ponds that feed on mosquito larvae, spraying of insecticides in ditches, drainage areas and swamps, etc. In addition, doors and windows should be provided with wire mesh to prevent the entry of mosquitoes.

Q6. In the given flow diagram, the replication of retrovirus in a host is shown. Observe and answer the following questions.
a. Fill in (1) and (2)
b. Why is the virus called retrovirus?
c. Can the infected cell survive while viruses are being replicated and released?

Answer: (a) 1. Viral DNA is produced by reverse transcriptase.
2. New viral RNA is produced by infected cell.
(b) HIV is called retrovirus because it forms DNA from RNA by reverse transcription.
(c) Yes, infected cell can survive while viruses are being replicated and released.

Q7. “Maintenance of personal and public hygiene is necessary for prevention and control of many infectious diseases”. Justify the statement giving suitable examples. 

Answer: Measures for personal hygiene include keeping the body clean; consumption of clean drinking water, food, vegetables, fruits, etc. Public hygiene includes proper disposal of waste and excreta; periodic cleaning and disinfection of water reservoirs, pools, cesspools and tanks, and observing standard practices of hygiene in public catering. These measures are particularly essential where the infectious agents are transmitted through food and water such as typhoid, amoebiasis and ascariasis.

Q8. The following table shows certain diseases, their causative organisms and symptoms. Fill the gaps.

Answer: 

Q9. The outline structure of a drug is given below.
a. Which group of drugs does this represent?
b. What are the modes of consumption of these drugs?
c. Name the organ of the body which is affected by consumption of these drugs.

Answer: (a) Cannabinoids
(b) Generally taken by inhalation and oral ingestion
(c) Affect the cardiovascular system of the body

Q10. Give the full form of CT and MRI. How are they different from each other? Where are they used?

Answer: CT (computed tomography) and MRI (magnetic resonance imaging) are very useful to detect cancers of the internal organs. Computed tomography uses X-rays to generate a three-dimensional image of the internals of an object. MRI uses strong magnetic fields and non-ionising radiations to accurately detect pathological and physiological changes in the living tissue.

Q11. Many secondary metabolites of plants have medicinal properties. It is their misuse that creates problems. Justify the statement with
an example.

Answer: Several plants, fruits and seeds having hallucinogenic properties and have been used for hundreds of years in folk-medicine, religious ceremonies and rituals all over the globe. When these are taken for a purpose other than medicinal use or in amounts/frequency that impairs one’s physical, physiological or psychological functions, it constitutes drug abuse.

Q12. Why cannabinoids are banned in sports and games?

Answer: As these days cannabinoids are being abused by some sports persons to increase their performance, that is why cannabinoids are banned in sports and games.

Q13. What is secondary metabolism?

Answer: Secondary metabolism is a term for pathways and small molecule products of metabolism that are not absolutely required for the survival of the organism. Examples of the products include antibiotics and pigments.

Q14. Drugs and alcohol give short-term ‘high’ and long-term ‘damages’, Discuss.

Answer: Curiosity, need for adventure and excitement, and experimentation, constitute common causes, which motivate youngsters towards drug and alcohol use. A child’s natural curiosity motivates him/her to experiment. This is complicated further by effects that might be perceived as benefits, of alcohol or drug use. Thus, the first use of drugs or alcohol may be out of curiosity or experimentation, but later the child starts using these to escape facing problems. Of late, stress, from pressures to excel in academics or examinations, has played a significant role in persuading the youngsters to try alcohol and drugs. The perception among youth that it is ‘cool’ or progressive to smoke, use drugs or alcohol, is also in a way a major cause for youth to start these habits. Television, movies, newspapers, internet also help to promote this perception. Other factors that have been seen to be associated with drug and alcohol abuse among adolescents are unstable or unsupportive family structures and peer pressure.

Q15. Diseases like dysentery, cholera, typhoid etc., are more common in over crowded human settlements. Why?

Answer: Diseases like dysentery, cholera, typhoid etc., are more common in overcrowded human settlements because these are infectious diseases that can transmitted from one person to another. In overcrowded settlements there is more chances of transmission of disease from one person to other.

Q16. From which plant cannabiniods are obtained? Name any two cannabinoids. Which part of the body is effected by consuming these substances?

Answer: Cannabinoids are obtained from the inflorescence of the plant Cannabis sativa. Marijuana, hashish, charas, ganja are some of the cannabinoids. These chemicals interact with cannabinoid receptors of the body, mainly present in the brain. Cardiovascular system is affected adversely.

Q17. In the metropolitan cities of India, many children are suffering from allergy/asthma. What are the main causes of this problem. Give some symptoms of allergic reactions. 

Answer: Allergy is the exaggerated response of the immune system of certain antigens present in the environment. In metropolitan cities life style is responsible for lowering of immunity and sensitivity to allergens. More polluted environment increases the chances of allergy in children. Some symptoms of allergic reactions are sneezing, watery eyes, running nose and difficulty in breathing.

Q18. What is the basic principle of vaccination? How do vaccines prevent microbial infections? Name the organism from which hepatitis B Vaccine is produced.

Answer: The principle of vaccination is based on the property of ’memory’ of the immune system. In vaccination, a preparation of antigenic proteins of pathogens or inactivated/live but weakened pathogens is introduced into the body. The antigens generate the primary immune response by producing antibodies. The vaccines also generate the memory B-cells and T-cells. When the vaccinated person is attacked by the same pathogens, the existing memory B-cells or T-cells recognise the antigen quickly and overwhelm the invaders with massive production of lymphocytes and antibodies. Hepatitis B vaccine is produced from yeast.

Q19. What is cancer? How is a cancer cell different from the normal cell? How do normal cells attain cancerous nature? 

Answer: An abnormal and uncontrolled division of cells is termed as Cancer. The cancerous cells are different from the normal cells in the following ways.

\(
\begin{array}{|c|l|c|l|}
\hline & \text { Cancer Cells } & & \text { Normal Cells } \\
\hline 1 . & \begin{array}{l}
\text { Cancer cells divide in an } \\
\text { uncontrolled manner. }
\end{array} & 1 . & \begin{array}{l}
\text { Normal cells divide in a } \\
\text { controlled manner. }
\end{array} \\
\hline 2 . & \begin{array}{l}
\text { The cells do not show contact } \\
\text { inhibition. }
\end{array} & 2 . & \begin{array}{l}
\text { The cells show contact } \\
\text { inhibition. }
\end{array} \\
\hline 3 . & \text { Life span is indefinite. } & 3 . & \text { Life span is definite. } \\
\hline
\end{array}
\)

In our body, the growth and differentiation of cells is highly controlled and regulated. The normal cells show a property called contact inhibition. The surrounding cells inhibits uncontrolled growth and division of cells. The normal cells lose this property and become cancerous cells giving rise to masses of cells called tumors. Transformation of normal cells into cancerous cells is induced by some physical, chemical and biological agents (carcinogens).

Q20. A person shows strong unusual hypersensitive reactions when exposed to certain substances present in the air. Identify the condition. Name the cells responsible for such reactions. What precaution should be taken to avoid such reactions.

Answer: Allergy. Mast Cells are responsible for such reactions. To avoid such reactions following precautions must be taken:
(i) The use of drugs like antihistamine, adrenalin and steroids quickly reduce the symptoms of allergy.
(ii) Avoid contact with substances to which a person is hypersensitive.

Q21. For an organ transplant, it is an advantage to have an identical twin. Why?

Answer: Very often, when some human organs like heart, eye, liver, kidney fail to function satisfactorily, transplantation is the only remedy to enable the patient to live a normal life. Then a search begins – to find a suitable donor.
Grafts from just any source – an animal, another primate, or any human beings cannot be made since the grafts would be rejected sooner or later. Tissue matching, blood group matching are essential before undertaking any graft/transplant and even after this the patient has to take immuno-suppresants all his/her life. The body is able to differentiate ‘self ’ and ‘nonself’ and the cell-mediated immune response is responsible for the graft rejection. In an identical twin there is no chance of rejection of transplanted organ, so it is advantageous.

Q22. What are lifestyle diseases? How are they caused? Name any two such diseases.

Answer:  Lifestyle diseases are defined as diseases linked with the way people live their life. This is commonly caused by alcohol, drug and smoking abuse as well as lack of physical activity and unhealthy eating. Diseases that impact on our lifestyle are heart disease, stroke and obesity.

Q23. If there are two pathogenic viruses, one with DNA and other with RNA, which would mutate faster? And Why? 

Answer: Both DNA and RNA are able to mutate. In fact, RNA being unstable, mutate at a faster rate. Consequently, viruses having RNA genome and having shorter life span mutate and evolve faster.

LONG ANSWER TYPE QUESTIONS

Q1. Represent schematically the life cycle of a malarial parasite.

Answer: 

Q2. Compare the life style of people living in the urban areas with those of rural areas and briefly describe how the life style affects their health.

Answer: Urban areas
The social environment: Urban environments are more likely to see higher rates of crime and violence. 
The physical environment: In densely populated urban areas, there is often a lack of facilities and outdoor areas for exercise. In addition, air quality is often lower in urban environments which can contribute to chronic diseases such as asthma. In the developing world, urban dwellers often live in large slums which lack basic sanitation and utilities such as water and electricity. Access to health and social service: Persons of lower socioeconomic status are more likely to live in urban areas and are more likely to lack health insurance. The high prevalence of individuals without health insurance or citizenship creates a greater burden on available systems.
Rural areas
The social environment: Rural dwellers have significantly poorer health status than urban elders. Also, rural residents smoke more, exercise less, have less nutritional diets.
The physical environment: Rural women especially less educated women, are more sedentary than urban women. While poor air quality and crime rates are likely to be less of an issue in rural areas, insufficiencies in the built environment make it difficult for rural residents to exercise and maintain healthy habits.
Access to health and social seryice: Evidence indicates that rural residents have limited access to health care. Some rural areas have a higher proportion of uninsured and individually insured residents than urban areas.

Q3. Why do some adolescents start taking drugs. How can this be avoided?

Answer: The reasons why adolescents and youngsters take to consumption of drugs are:
(i) Curiosity of child motivates him/her to experiment.
(ii) Need for adventure and excitement.
(iii) Peer group pressure
(iv) Desire to do more physical and mental work.
(v) To overcome frustration and depression, due to failure in examinations or in other activities.
(vi) Unstable or unsupportive family structures.
The following measures can be taken to avoid taking drugs:
(i) Avoid undue pressure on child to perform beyond his/her capability in studies, sports ox any other activities.
(ii) Education and counselling are very important to face problem of stress and failure in life.
(iii) Seeking help from parents, elders and peers. This would help the young to share their feelings and concern.
(iv) Looking for danger signs and taking appropriate measures to treat them.
(v) Seeking professional and medical help for de-addiction and rehabilitation.

Q4. In your locality, if a person is addicted to alcohol, what kind of behavioural changes do you observe in that person? Suggest measures to over come the problem.

Answer: The immediate adverse effects of drugs and alcohol abuse are manifested in the form of reckless behaviour, vandalism and violence. Excessive doses of drugs may lead to coma and death due to respiratory failure, heart failure or cerebral hemorrhage. A Combination of drugs or their intake along with alcohol generally results in overdosing and even deaths. The most common warning signs of drug and alcohol abuse among youth include drop in academic performance, unexplained absence from school/college, lack of interest in personal hygiene, withdrawal, isolation, depression,, fatigue, aggressive and rebellious behaviour, deteriorating relationships with family and friends, loss of interest in hobbies, change in sleeping and eating habits, fluctuations in w’eight, appetite, etc. There may even be some far-reaching implications of drug/alcohol abuse. If an abuser is unable to get money to buy drugs/alcohol he/she may turn to stealing. The adverse effects are just not restricted to the person who is using drugs or alcohol. At times, a drug/ alcohol addict becomes the cause of mental and financial distress to his/her entire family and friends.
The age-old adage of prevention is better than cure’ holds true here also. It is also true that habits such as smoking, taking drug or alcohol are more likely to be taken up at a young age, more during adolescence. Hence, it is best to identify the situations that may push an adolescent towards use of drugs or alcohol, and to take remedial measures well in time. In this regard, the parents and the teachers have a special responsibility. Parenting that combines with high levels of nurturance and consistent discipline, has been associated with lowered risk of substance (alcohol/drugs/tobacco) abuse. Some of the measures mentioned here would be particularly useful for prevention and control of alcohol and drugs abuse among adolescents.

Q5. What are the methods of cancer detection? Describe the common approaches for treatment of cancer.

Answer: Cancer detection and diagnosis: Early detection of cancers, is essential as it allows the disease to be treated successfully in many cases. Cancer detection is based on biopsy and histopathological studies of the tissue and blood and bone marrow tests for increased cell counts in the case of leukemias. In biopsy, a piece of the suspected tissue cut into thin sections is stained and examined under microscope (histopathological studies) by a pathologist. Techniques like radiography (use of X-rays), CT (computed tomography) and MRI (magnetic resonance imaging) are very useful to detect cancers of the internal organs. Computed tomography uses X-rays to generate a three-dimensional image of the internals of an object. MRI uses strong magnetic fields and non-ionising radiations to accurately detect pathological and physiological changes in the living tissue.

• Antibodies against cancer-specific antigens are also used for detection of certain cancers. Techniques of molecular biology can be applied to detect genes in individuals with inherited susceptibility to certain cancers. Identification of such genes, which predispose an individual to certain cancers, may be very helpful in prevention of cancers. Such individuals may be advised to avoid exposure to particular carcinogens to which they are susceptible (e.g., tobacco smoke in case of lung cancer).
• Treatment of cancer: The common approaches for treatment of cancer are surgery, radiation therapy and immunotherapy. In radiotherapy, tumor cells are irradiated lethally, taking proper care of the normal tissues surrounding the-tumor mass. Several chemotherapeutic drugs are used to kill cancerous cells. Some of these are specific for particular tumors. Majority of drugs have side effects like hair loss; anemia, etc. Most cancers are treated by combination of surgery, radiotherapy and chemotherapy. Tumor cells have been shown to avoid detection and destruction by immune system. Therefore, the patients are given substances called biological response modifiers such as a-interferon which activates their immune system and helps in destroying the tumor.

Q6. Drugs like LSD, barbiturates, amphetamines, etc., are used as medicines to help patients with mental illness. However, excessive doses and abusive usage are harmful. Enumerate the major adverse effects of such drugs in humans.

Answer: Drugs like barbiturates, amphetamines, benzodiazepines, and other similar drugs, that are normally used as medicines to help patients cope with mental illnesses like depression and insomnia, are often abused. Morphine is a very effective sedative and painkiller, and is very useful in patients who have undergone surgery. Several plants, fruits and seeds having hallucinogenic properties have been used for hundreds of years in folk-medicine, religious ceremonies and rituals all over the globe. When these are taken for a purpose other than medicinal use or in amounts/frequency that impairs one’s physical, physiological or psychological functions, it constitutes drug abuse. 

Q7. What is Pulse Polio Programme of Government of India? What is OPV? Why is it that India is yet to eradicate Polio?

Answer: Pulse Polio is an immunisation campaign established by the government of India to eliminate poliomyelitis (polio) in India by vaccinating all children under the age of five years against the polio virus. The project fights poliomyelitis through a large-scale pulse vaccination programme and monitoring for polio cases.

•  In 1995, following the Global Polio Eradication Initiative of the World Health Organization (1988), India launched Pulse Polio immunisation program with Universal Immunization Program which aimed at 100% coverage.
• The last reported cases of wild polio in India were in West Bengal and Gujarat on 13 January 2011. On 27 March 2014, the World Health Organization (WHO) declared India a polio free country, since no cases of wild polio had been reported in for three years.
•  Polio vaccines are the vaccines used to prevent poliomyelitis (polio).One type uses inactivated poliovirus and is given by injection (IPV), while the other type uses weakened poliovirus and is given by mouth (OPV). The World Health Organization recommends all children be vaccinated against polio. The two vaccines have eliminated polio from most of the world. The oral polio vaccine was developed by Albert Sabin and came into commercial use in 1961.

Q8. What are recombinant DNA vaccines? Give two examples of such vaccines. Discuss their advantages.

Answer: A recombinant vaccine is a vaccine produced through recombinant DNA technology. This involves inserting the DNA encoding an antigen that stimulates an immune response into bacterial or mammalian cells.
Recombinant DNA technology has allowed the production of antigenic polypeptides of pathogen in bacteria or yeast. Vaccines produced using this approach allow large scale production and hence greater availability for immunisation, e.g., hepatitis B vaccine (Recombivax HB) produced from yeast. As of June 2015 one human DNA vaccine had been approved for human use, the single-dose Japanese encephalitis vaccine called IMOJEV, released in 2010 in Australia.
Advantages of recombinant DNA vaccines:
1. No risk for infection
2. Ease of development and production
3. Stability for storage and shipping
4. Cost-effectiveness
5. Expression and purification of recombinant proteins
6. Long-term persistence of immunogen
7. In vivo expression ensures protein more closely resembles normal eukaryotic structure, with accompanying post-translational modifications.