Category: Class 12 Biology Objective Questions

Biology Multiple Choice Questions on “Human Health and Disease – Allergies”.

1. Anaphylactic shock is _______
a) Mild local reaction to an allergen
b) Severe local reaction
c) The severe reaction of the whole body
d) The mild reaction of the whole body
Answer: c
Clarification: Anaphylactic shock is a severe reaction to the whole body. It is a hypersensitive reaction of the body to a foreign substance like a bee sting, penicillin, serum protein, etc.

2. Hypersensitivity to an allergen is due to _________
a) Food Habits
b) Life style
c) Improper functioning of the immune system
d) Environment
Answer: c
Clarification: Hypersensitivity to an allergen is due to improper functioning of the immune system. Any result in the system results in discomfort, disease or even death of the organism.

3. The inflammatory response in allergy is due to the release of ________ by mast cells.
a) Antibodies
b) Antigens
c) Mucus
d) Histamine
Answer: d
Clarification: Inflammatory response in allergy is due to the release of histamine by mast cells. Histamine along with IgE antibodies act as allergy mediator. It dilates arteries and causes fluid accumulation which causes the inflammatory response.

4. Allergy is an infectious disease which usually spreads by touching infected patients.
a) True
b) False
Answer: b
Clarification: Allergy is a non-infectious unusual reaction or hypersensitivity of an individual to a foreign substance or agent that is harmless to other individuals.

5. Which of the following usually cannot act as an allergen?
a) Pure Water
b) Pollen
c) Dust
d) Shellfish
Answer: a
Clarification: Pure water usually cannot act an allergen to an individual because it is free of impurities. Allergen is any foreign substance or agent that produces hypersensitivity in an individual. For example, pollen, spores, dust, scent, wool, drugs like penicillin, egg white, fur, feathers, shellfish, etc.

6. What is meant by sensitisation of allergen?
a) When an allergen leaves the body
b) The first contact of an allergen
c) The incubation period of an allergen
d) When symptoms of the disease appear
Answer: b
Clarification: The allergen on first contact functions as a mild antigen. This process is called sensitisation. It produces antibodies which remain attached to the mast cells. These mast cells then release histamine and cause inflammatory responses in the body.

7. Which of the following is not a common manifestation of allergy?
a) Watering of Eyes
b) Oedema
c) Sneezing
d) Anaphylaxis
Answer: d
Clarification: Sneezing, Watering of Eyes, Oedema, Breathlessness, Coughing are some of the most common manifestations of allergy. Dust and mites are responsible for 40% of cases of allergy.

8. Which of the following diseases is an allergic response?
a) AIDS
b) Hay Fever
c) Yellow Fever
d) Syphilis
Answer: b
Clarification: Hay Fever is an allergic swelling and secretion of the mucous membrane of nose, throat and conjunctiva in response to pollen and spores. Itchy and watery eyes, sneezing and running nose are its most common symptoms.

9. Which of the following allergies is characterised by circumscribed raised pinkish blisters?
a) Hay Fever
b) Asthma
c) Eczema
d) Urticaria
Answer: d
Clarification: Urticaria is an allergic response characterised by multiple, circumscribed raised pinkish, itchy blisters persisting for a few days. They can be caused due to a reaction of any food, medicine or any other allergens.

10. Eczema appears to run in families who have a personal history of allergic reactions.
a) True
b) False
Answer: a
Clarification: Eczema is a form of dermatitis which starts with reddening of the skin, the formation of vesicles and forming of scales. It appears to run in families who have a personal history of allergic reactions.

11. Allergic reactions are countered by the administration of _________
a) Cortisol
b) Insulin
c) Antihistamine
d) Oxytocin
Answer: c
Clarification: Allergic reactions are countered by the administration of antihistamine, adrenaline and steroids that quickly reduce the symptoms of allergy. For determining the cause of the allergy, the patient is exposed to or injected with a very small dose of possible allergen and after that, the reactions on the body are studied.

Biology Multiple Choice Questions on “Plant Diseases and their Control”.

1. Which of the following is not a method by which pathogens affect the yield of crops?
a) Reduce the quantity of yield
b) Reduce the quality of crop produce
c) Increase in cost production
d) Increase the flowering period
Answer: d
Clarification: Pathogens affect the crop yield by reducing the quantity of yield and reducing the quality of crop produce. Pathogens also increase the production cost due to reduced yield and expenditure on pesticides.

2. Which of the following is not a method of the perpetuation of disease by the pathogen?
a) The entry of pathogen through natural openings
b) Reproduction by pathogen
c) Reducing the quantity of yield
d) Direct penetration of the pathogen
Answer: c
Clarification: Various steps of the perpetuation of disease by the pathogen are coming of a pathogen in contact with host plants, entry of the pathogen into the host through natural openings, wounds or direct penetrations, the establishment of the pathogen inside the host, reproduction of pathogen, etc.

3. Which of the following is not a method of reducing total biomass of crop?
a) Damage to leaf tissues
b) Studying the crop
c) Killing branches
d) Stunting effect
Answer: b
Clarification: Diseases reduce the total biomass of the crop by causing damage to leaf tissues, stunting effect, damage to reproductive structures like flowers, fruits and seeds, killing of branches. This all results in the death of the plant.

4. Plant diseases are broadly classified into nonparasitic and parasitic.
a) True
b) False
Answer: a
Clarification: Plant diseases are broadly classified into two categories, nonparasitic and parasitic. Nonparasitic diseases are non-transmissible and are caused by physiological disorders due to defective heredity or unfavourable environment. Parasitic diseases are transmissible diseases which are caused by various categories of pathogens.

5. Which of the following is not related to Necrosis?
a) Curling of leaves
b) Death of tissues
c) A common symptom of fungal diseases
d) Discolouration of leaves
Answer: a
Clarification: Necrosis is the death of plant tissue or can be characterised by discolouration of areas on leaves, stems and roots. It is a common symptom in fungal diseases but also occurs in bacterial and viral diseases.

6. Necrosis cannot be in the form of _________
a) Lesions
b) Scabs
c) Cankers
d) Rots
Answer: d
Clarification: Necrosis cannot be in the form of rots. It may be in the form of local lesions, cankers (necrotic lesions often sunken, exposing the interior), blights (burnt up appearance), scabs (roughened, crust-like lesions) and dieback (death and necrosis beginning form tip of branches towards the base).

7. Which of the following is not related to Rots?
a) Discolouration of tissue
b) Degeneration of succulent tissue
c) Distortion of leaves
d) It is of two types
Answer: c
Clarification: Rots is the discolouration, softening and degeneration of a succulent tissue due to fungal or bacterial infection. It is of two types- Dry rot (Rot is without an oozing) and Soft rot (Rot is accompanied by oozing).

8. Wilting is the loss of turgidity and drooping of leaves.
a) True
b) False
Answer: a
Clarification: Wilting is the loss of turgidity and drooping of leaves or shoots generally due to insufficiency of water. The pathogens usually block the vascular tissue for bringing wilt. It occurs in response to both bacterial and fungal infections.

9. Which of the following is not true regarding Chlorosis?
a) Yellowing of leaves
b) Death of plant tissues
c) Non-formation of chlorophyll
d) Destruction of chlorophyll
Answer: b
Clarification: Chlorosis is the yellowing of green tissues or structures (especially leaves) due to either non-formation or destruction of chlorophyll. Chlorosis is quite common in the case of mineral deficiency. It also occurs in response to fungal, bacterial and viral infections.

10. Which of the following is not a common symptom of plant disease?
a) Necrosis
b) Leaf curls
c) Perfect flowering
d) Chlorosis
Answer: c
Clarification: The common symptoms of plant diseases include Necrosis, Pustules, Pitting, Rots, Leaf curls, Excessive growth of tissues, Stunting, Chlorosis, Wilting, Mosaics, Root Galls, Damping-off and excessive root branching.

Biology Multiple Choice Questions on “Tools of Recombinant DNA Technology: Restriction Enzymes”.

1. From which organism was the first restriction enzyme isolated?
a) Escherichia coli
b) Salmonella typhimurium
c) Bacillus cereus
d) Staphylococcus aureus
Answer: a
Clarification: The restriction enzymes are molecular scissors that cleave the DNA at specific recognition sites. They were first isolated from Escherichia coli in the year 1963.

2. In genetic engineering, restriction enzymes cleave the DNA at a specific site known as _____
a) restriction
b) recognition
c) promoter
d) sense
Answer: b
Clarification: Restriction enzymes cleave the DNA at a specific sequence known as recognition sequence. These sequences are highly specific for each enzyme.

3. Restriction enzymes are also known as _________
a) ligase
b) polymerase
c) telomerase
d) restriction endonucleases
Answer: d
Clarification: Restriction enzymes are also known as restriction endonucleases or restrictase. They are chemical knives (scissors) used in genetic engineering or recombinant DNA technology.

4. _____ was the first restriction endonuclease was isolated and characterized.
a) EcoRI
b) BamHI
c) Hind II
d) Sma I
Answer: c
Clarification: Hind II was the first restriction endonuclease to be isolated and characterized. It cuts the DNA by recognizing a specific sequence of six base pairs. It was isolated from the bacteria called Haemophilus influenzae.

5. Restriction enzymes belong to a larger class of enzymes called ______
a) proteins
b) proenzyme
c) nucleases
d) isozymes
Answer: c
Clarification: Restriction enzymes belong to a larger class of enzymes called nucleases. There are two types of nucleases. They are: exonucleases and endonucleases.

6. The _______ in DNA are base pair sequences that are the same when read forward or backward from a central axis of symmetry.
a) nucleases
b) palindrome
c) termination sequences
d) amino acids
Answer: b
Clarification: Palindromes are a group of letters that form the same words when read forward (left to right) or backward (right to left). For example: NAYAN, MALAYALAM, etc.

7. Fragments of DNA formed after treatment with endonucleases are separated by the technique of _______
a) polymerase chain reaction
b) gene amplification
c) blotting
d) gel electrophoresis
Answer: d
Clarification: DNA is a charged molecule. When fragmented, it can be separated by the technique called gel electrophoresis. It is a technique in which the molecules are separated based on the charge present on that molecule.

Biology MCQs for Class 12 on “Biotechnology Applications – Transgenic Animals – 3”.

1. Transgenic mice are being developed for use in testing the safety of vaccines before they are used on ________
a) cattle
b) humans
c) pigs
d) monkeys
Answer: b
Clarification: Transgenic mice are being developed for use in testing the safety of vaccines before they are used on humans. They have been successfully used to test the safety of the polio vaccine.

2. Vaccines are normally tested on ______ before using on humans.
a) pigs
b) cattle
c) monkeys
d) mice
Answer: c
Clarification: Non-primate humans are extensively used for testing vaccine safety. Monkeys are usually used because they show similar reactions to any antigen as that of humans.

3. Chemical safety testing is also known as _______ testing.
a) therapeutic
b) physical
c) toxicity
d) transgenic
Answer: c
Clarification: Chemical safety testing is also known as toxicity testing. It is said so because it measures the amount of toxic (chemical) substance in a sample that may affect living or non-living environment. It is also called as toxicology testing.

4. Chemical safety testing is also known as _______ testing.
a) transgenic
b) therapeutic
c) physical
d) safety
Answer: d
Clarification: Chemical safety testing is also known as safety testing. It is a process used to test the safety of any sample such as food from a chemical (toxin) which may affect living or non-living environment.

5. The procedure of chemical safety testing is the same as that used for testing _______ of drugs.
a) anatomy
b) toxicity
c) basicity
d) acidity
Answer: b
Clarification: The procedure of chemical safety testing is the same as that used for testing the toxicity of drugs. Since toxic substances contain various chemicals, the testing procedure for both i.e. toxins and chemical safety is the same.

6. The genes carried by transgenic animals make them more ______ to toxic substances as compared to non-transgenic animals.
a) strong
b) sensitive
c) infective
d) resistant
Answer: b
Clarification: The genes carried by transgenic animals make them more sensitive to toxic substances as compared to non-transgenic animals. This happens because the newly inserted gene may or may not act against that particular toxin making them more susceptible to it.

7. To study the effects of the incorporated gene(s), the ________ animals are subjected to toxic substances.
a) infectious
b) normal
c) transgenic
d) non-transgenic
Answer: c
Clarification: To study the effects of the incorporated gene(s), the transgenic animals are subjected to toxic substances. These animals are developed by incorporating a foreign gene within them which is used to study the function of that particular gene. This gene may or may not act against the toxin.

8. Toxicity testing in transgenic animals will allow us to obtain results in ______ time.
a) less
b) appropriate
c) extra
d) more
Answer: a
Clarification: Toxicity testing in transgenic animals will allow us to obtain results in less time. This happens because transgenic animals are sensitive towards ant toxin or show immediate reactions. Thus these animals can also be used for testing the safety of vaccines.

To practice Biology MCQs for Class 12,

Biology Multiple Choice Questions on “Growth Models – 1”.

1. What is a sigmoid growth curve called?
a) Exponential growth curve
b) Logistic growth curve
c) Declining growth curve
d) Interacting curve
Answer: b
Clarification: A sigmoid growth curve is also called a logistic growth curve. It is considered to be a realistic curve. It is obtained due to the finite and limited source of resources in a population. It is also called a Verhulst-Pearl Logistic Growth curve.

2. How many phases does a logistic growth curve have?
a) 5
b) 8
c) 1
d) 4
Answer: a
Clarification: A logistic (sigmoidal) growth curve has 5 phases. They are lag phase, log phase, deacceleration phase, negative down acceleration phase, and stationary phase.

3. Which is the initial phase in logistic growth?
a) Log phase
b) Lag phase
c) Declining phase
d) Stationary phase
Answer: b
Clarification: The initial phase of logistic growth is the lag phase. It has 5 phases. It is the phase in which the population increases slowly and tends to adopt the new environment. The population density increases in the positive acceleration phase.

4. What do organisms in a population do in the lag phase?
a) Grow at a slower rate
b) Grow at a faster rate
c) Death
d) Tend to adapt
Answer: d
Clarification: The lag phase is the initial phase of a growth curve in which the population increases slowly. In this phase, the population tries to adopt the new environment. The population density increases in the positive acceleration phase.

5. Which of the following initial phase is slow?
a) Declaration phase
b) Stationary phase
c) Lag phase
d) Log phase
Answer: c
Clarification: The lag phase is initial and slow. It is the phase in which the population increases slowly and tends to adopt the new environment. The population density increases in the positive acceleration phase.

6. Which is the second phase of the sigmoidal growth curve?
a) Deceleration phase
b) Log phase
c) Exponential phase
d) Stationary phase
Answer: b
Clarification: The second phase of the sigmoid (logistic) growth curve is the log phase. It is the logarithmic, exponential growth phase in which organisms multiply at a faster rate.

7. In which of the following phase do organisms in a population multiply at a faster rate?
a) Deceleration phase
b) Stationary phase
c) Exponential phase
d) Log phase
Answer: d
Clarification: The organisms multiply at a faster rate in the log phase. It is the second phase of the sigmoid (logistic) growth curve. And the maximum growth of the population is observed in this phase.

8. Which is the third phase in the logistic growth curve of the population?
a) Log phase
b) Deacceleration phase
c) Lag phase
d) Negative phase
Answer: c
Clarification: The third phase in the logistic growth of the population is the deacceleration phase. In this phase, the organisms increase slowly. This happens due to limited resources.

9. What happens in the deacceleration phase?
a) Grow at a faster rate
b) Tend to adapt
c) Death
d) Organisms increase slowly
Answer: d
Clarification: In the deacceleration phase, the organisms increase slowly. This happens due to limited resources. It is the third phase of a sigmoid/ logistic/ S-shaped growth curve.

10. What happens in the negative down acceleration phase?
a) Grows at a faster rate
b) Growth gradually increase
c) Organisms growth gradually reduce
d) Death
Answer: c
Clarification: The negative down acceleration phase is the fourth phase of a sigmoid/ logistic/ S-shaped growth curve. In this phase the population density gradually reduces.

11. In which phase population achieves zero growth?
a) Growing phase
b) Stationary phase
c) Lag phase
d) Log phase
Answer: b
Clarification: The population achieves zero growth in the stationary phase. It is the last phase of logistic growth. It is due to many reasons such as exhaustion of resources, aging, etc.

12. Which letter is used to designate the carrying capacity of a population?
a) A
b) S
c) K
d) N
Answer: c
Clarification: The carrying capacity of a population is designated by the letter ‘K’. The resources in a given habitat can be used by the maximum possible number of a population; beyond this, no further growth is seen in a population. This is known as the carrying capacity of that species in that habitat.

13. When responses in a population are limiting which growth is observed?
a) Increasing growth
b) Logistic growth
c) Decreasing growth
d) Stationary growth
Answer: b
Clarification: Logistic growth is seen when resources in a population are limiting. It has 5 phases. It is also known as the sigmoid/ S-shaped growth curve. It is a more realistic growth model.

14. When responses in a population are unlimited which growth is observed?
a) Logistic growth
b) Decreasing growth
c) Lag phase growth
d) Exponential growth
Answer: d
Clarification: An exponential growth is observed when resources in the population are unlimited. The population grows in geometric fashion and results in a J-shaped curve.

15. Exponential growth is observed in which fashion?
a) Geometric
b) Algebraic
c) Declining
d) Steady
Answer: a
Clarification: The exponential growth is in which the population continues to multiply in a geometric fashion. It results in a J-shaped curve. It is obtained when the resources in the population are unlimited.