Category: Class 12 Biology Objective Questions

Biology Multiple Choice Questions on “Inheritance and Variation Principles – Mendelian Disorders”.

1. People suffering from colour blindness fail to distinguish which of the two colours?
a) Red and Green
b) Blue and Green
c) Red and Blue
d) Red and Yellow
Answer: a
Clarification: People who are colour blind fail to distinguish between red and green colours. Colour blindness is a sex-linked recessive trait in which the normal gene and its recessive allele are carried by X-chromosome.

2. When can a female be colour blind?
a) Father has normal vision and the mother is a carrier
b) Father has normal vision and mother is colour blind
c) Father is colour blind and the mother has a normal vision
d) Father is colour blind and mother is a carrier
Answer: d
Clarification: A female can be a colour blind only in two conditions:
i. When her father is colour blind and her mother is the carrier of this disease
ii. When both her father and her mother are colour blind
Therefore, for a female to be colour blind, her father must also have colour blindness.

3. Which of the following type of inheritance is shown by colour blindness?
a) Chromosomal inheritance
b) Criss-cross inheritance
c) Zig-zag inheritance
d) Up-down inheritance
Answer: b
Clarification: Colour-blindness is a sex-linked trait which shows criss-cross inheritance which means male transmits his trait to his grandson through his daughter, while a female transmits the traits to her granddaughter through her son.

4. What will be the percentage of sons having a normal vision if the father has normal vision and their mother is colour blind?
a) 0%
b) 25%
c) 50%
d) 100%
Answer: a
Clarification: The percentage of sons having normal vision, if the father has normal vision and mother is colour blind is 0% because as colour blindness is a sex-linked trait, it means that the trait only transmits through X-chromosome. As the mother is colour blind, both her gametes will carry the gene for colour blindness, so none of their sons will have a normal vision.

5. What percentage of children are colour blind if their father is colour blind and the mother is a carrier for Colour blindness?
a) 25%
b) 50%
c) 75%
d) 100%
Answer: b
Clarification: The percentage of children which are colour blind if their father is colour blind and the mother is a carrier for colour blindness is 50% because the father will produce Xc and Y chromosome and the mother will produce Xc and X chromosomes. Their children will have the genotypes- XcY, XY, XcXc and XcX. Therefore, 50% of children are colour blind, 25% have normal vision and 25% are the carriers of the disease.

6. Haemophilia is an autosomal recessive trait.
a) True
b) False
Answer: b
Clarification: No, haemophilia is not an autosomal recessive trait. It is X-linked recessive trait and shows transmission from normal carrier female to a male progeny. In this disease, the exposed blood of affected individuals cannot coagulate due to the presence of defective blood clotting factors.

7. How can a female be haemophilic?
a) Mother is haemophilic and father is normal
b) Mother is a carrier and father is haemophilic
c) Both mother and father are carriers
d) Both mother and father are haemophilic
Answer: b
Clarification: A female can only be haemophilic if her mother is at least a carrier of this disease and her father is haemophilic. But the possibility of a female becoming haemophilic is extremely rare because being haemophilic for the parents at the later stage of life is unviable.

8. What is the full form of AHG?
a) Anti haemophilic globulin
b) Anti haemoglobin
c) Allergic haemoglobin
d) Allergic haemophilic globulin
Answer: a
Clarification: AHG stands for Anti haemophilic globulin. It is a type of blood protein which is required for normal blood clotting. The person suffering from haemophilia A cannot synthesise this protein and even a small cut may lead to continuous bleeding for a long time.

9. What is the percentage of children being a carrier of haemophilia if their mother is a carrier and their father is a normal man?
a) 25%
b) 50%
c) 75%
d) 100%
Answer: a
Clarification: The percentage of children being a carrier of haemophilia if their mother is a carrier and their father is a normal man is 25% because the gametes formed by mother are X and X^h while the gametes formed by father are X and Y. The genotype of the offspring obtained would be XY, XX, XX^h and X^hY. Thus 50% of children are normal, 25% are carriers of haemophilia and 25% are haemophilic (only son).

10. How many genotypes of sickle cell anaemia are possible in a population?
a) One
b) Two
c) Three
d) Four
Answer: c
Clarification: Three types of genotypes of sickle cell anaemia are possible in a population. These are:
i. Hb^A Hb^A: Normal individuals
ii. Hb^A Hb^S: Normal individuals but act as a carrier in spreading the disease
iii. Hb^S Hb^S: Diseased individuals and they die before attaining maturity

11. Heterozygous individuals of sickle cell anaemia are severely affected by the disease.
a) False
b) True
Answer: a
Clarification: No, heterozygous individuals of sickle cell anaemia are not severely affected by the disease. Apparently, they appear to be unaffected by the disease. But, there is a 50% probability of transmission of the mutant gene to the progeny.

12. Which of the following statements are correct with respect to the figures given?

a) 1 represents normal WBCs
b) 1 represents normal RBCs
c) 2 represents abnormal RBCs
d) 2 represents normal RBCs
Answer: b
Clarification: 1^st figure represents the micrograph of RBCs from a normal individual while the 2^nd figure represents the micrograph of RBCs from an individual affected with sickle-cell anaemia. The RBCs of a normal individual are biconcave shaped while that of sickle cell anaemia are elongated sickle-like structure.

13. In which of the following places thalassemia is not common?
a) Indian subcontinent
b) South-east Africa
c) Mediterranean
d) North America
Answer: d
Clarification: Thalassemia is not common in North America. It is common in the Middle East, Indian subcontinent, Mediterranean and South-east Africa. It originated in the Mediterranean region and is caused by the deletion or mutation of the chromosomes.

14. By which of the following defects, thalassemia is caused?
a) Defects in RBCs
b) Defects in WBCs
c) Defects in platelets
d) Defects in lymphocytes
Answer: a
Clarification: The defect in the synthesis of globin polypeptide in RBC causes a group of disorders known as thalassemia. Absence or reduced synthesis of one of the globin chains leads to the excess of other chains which accumulate in our body to causes different diseases.

15. Which of the following statements is incorrect with respect to alpha-thalassemia?
a) Involves the genes HBA1 and HBA2
b) Inherited in a Mendelian dominant fashion
c) Connected to the deletion of the 16p chromosome
d) Result in decreased α-globin production
Answer: b
Clarification: Alpha-thalassemia is not inherited in a Mendelian dominant fashion. Instead, it is inherited in a Mendelian recessive fashion. It involves the genes HBA1 and HBA2 and it is also connected to the deletion of the 16p chromosome.

16. Which of the chromosome mutation leads to Beta-thalassemia?
a) 21
b) 10
c) 11
d) 13
Answer: c
Clarification: The mutation in the HBB gene on chromosome number 11 leads to the disorder beta-thalassemia. It is inherited as an autosomal recessive trait. The severity of beta-thalassemia depends upon the nature of the mutation.

Biology Multiple Choice Questions on “Mechanism of Evolution”.

1. Hugo de Vries did an experiment on which plant to prove mutation theory?
a) Evening primrose
b) Morning primrose
c) Night primrose
d) Pea pant
Answer: a
Clarification: Hugo de Vries proved mutation theory by doing experiments on Oenothera lamarckian, also known as evening primrose. It was from this plant; he came up with the observations. It is a complex heterozygous plant with a chromosomal aberration.

2. Which of the following does not belong to Mutation theory?
a) It can appear in all direction
b) It is the raw material of evolution
c) It appears suddenly
d) It is a continuous process
Answer: d
Clarification: Mutation is a jerky and discontinuous process. Otherwise, it can appear in all direction and are inheritable. Also, it can appear suddenly and produce their effect immediately.

3. _______ is termed as single-step large mutation.
a) Separation
b) Saltation
c) Anti mutation
d) Infinite mutation
Answer: b
Clarification: Single-step that causes large mutation is called saltation. It is called as such because the mutation occurs suddenly and abruptly that leads to evolution in large scale. Hugo de Vries used this term against Darwin’s theory of evolution.

4. Mutations are small and directional whereas Darwinism variations are random and directionless.
a) True
b) False
Answer: b
Clarification: It is a wrong statement. The statement should be in opposite manner i.e. mutations are random and directionless, whereas Darwinism variations are small and directional.

5. Which of the following point favor mutation theory?
a) Mutations are not very common
b) Mutations are mostly recessive
c) Mutation give rise to new varieties
d) Evening primrose is not a normal plant
Answer: c
Clarification: A number of mutations appear in nature and some mutations are also induced which have given rise to variations. This theory could explain both progressive and retrogressive evolution. The remaining options are against mutation theory.

6. Mutation theory couldn’t explain _______
a) development of mimicry
b) saltation
c) variations
d) chromosomes of flowers
Answer: a
Clarification: One of the drawbacks of mutation theory was that it couldn’t explain the development of mimicry, the relationship between the position of nectars in flower and also length of proboscis in their insect pollinators. The problem was that these cannot be imagined to have developed all of a sudden.

7. Who proposed the Evolutionary species concept?
a) Hugo de Vries
b) Charles Robert Darwin
c) George Gaylord Simpson
d) Gregor Johann Mendel
Answer: c
Clarification: Evolutionary species concept was given by George Gaylord Simpson. According to this concept, a species is an ancestor sequence of the population that evolved separately from other species and has its own evolutionary role and tendencies. This concept also includes evolution.

8. Which is the most accepted concept of species?
a) Biological species concept
b) Evolutionary species concept
c) Polytypic species concept
d) Typological species concept
Answer: d
Clarification: Typological species concept is the most accepted concept of species. According to this concept, a fixed pattern of characters is visible in the species of every living organism. All the members of that species show maximum resemblance with this pattern.

9. The process of formation of one or more new species from an existing species is called ______
a) Speciation
b) Saltation
c) Mutation
d) Radiation
Answer: a
Clarification: The process of formation of one or more species from an existing species is called Speciation. It is of two types, mainly: Divergent speciation and Transformation speciation. Speciation was one of the main theories of Darwin.

10. The local population of a particular area is known by a term called ______
a) Locals
b) Race
c) Villagers
d) Demes
Answer: d
Clarification: Local population of a particular area is called demes. The members of two different demes of the same species can interbreed. Races are small groups of species which are geographically isolated and have some genetic difference, which is controlled by genes.

Biology Multiple Choice Questions on “Protozoan Diseases in Humans”.

1. Entamoeba histolytica causes _________
a) dysentery
b) elephantiasis
c) small Pox
d) mumps
Answer: a
Clarification: Entamoeba histolytica is a pathogen which causes Amoebic Dysentery. Wuchereria bancrofti, Variola virus and Paramyxo virus cause Elephantiasis, Small Pox and Mumps respectively.

2. Entamoeba histolytica is found in _________
a) Stomach
b) Brain
c) Small Intestine
d) Large Intestine
Answer: d
Clarification: Entamoeba histolytica causes Amoebic Dysentery or Amoebiasis in the large intestine of humans. Its symptoms include constipation, abdominal pain, cramps and stools with excess mucus and blood clots.

3. The pathogen causing Amoebiasis is transmitted through which of the following?
a) By touch
b) Insect bite
c) Food or water contaminated with cysts
d) Droplet Infection
Answer: c
Clarification: Pathogen which causes Amoebiasis is Entamoeba histolytica. Certain carriers and vectors serve to transmit the parasite from faeces of the infected person to food and food products, thereby contaminating them. So the intake of contaminated food and water are the main source of infection.

4. Which of the following act as mechanical carriers to transmit Entamoeba histolytica?
a) Housefly
b) Caterpillar
c) Birds
d) Butterfly
Answer: a
Clarification: Houseflies act as mechanical carriers to transmit Entamoeba histolytica. Cysts of Entamoeba histolytica present in the stool of infected person are the source of infection.

5. Which of the following species of Plasmodium don’t cause Malaria?
a) Plasmodium piper
b) Plasmodium vivax
c) Plasmodium falciparum
d) Plasmodium malariae
Answer: a
Clarification: There are five species of Plasmodium which cause Malaria. These are Plasmodium vivax, Plasmodium falciparum, Plasmodium malariae, Plasmodium ovale and Plasmodium knowlesi.

6. Out of 5 species of Plasmodium, which one is the most virulent?
a) Plasmodium vivax
b) Plasmodium falciparum
c) Plasmodium malariae
d) Plasmodium knowlesi
Answer: b
Clarification: Plasmodium falciparum is the deadliest species of Plasmodium that cause malaria in humans. It is responsible for causing roughly 50 % of all malaria cases.

7. Where do the sexual stages of Plasmodium develop in its life cycle?
a) Gut of mosquito
b) Brain of human
c) Red Blood Corpuscles of human
d) Liver of human
Answer: c
Clarification: The sexual stages or the gametocytes of Plasmodium develops in Red Blood Corpuscles of the human. The female gametocytes or megagametocytes are round with food-laden cytoplasm and a small excentric nucleus. Male gametocytes or Microgametocytes have a clear cytoplasm and a large central nucleus. Both contain a large amount of haemozoin.

8. In which form Plasmodium enters the human body?
a) Phanerozoites
b) Cryptozoites
c) Gametocytes
d) Sporozoites
Answer: d
Clarification: Plasmodium enters the human body as sporozoites through the bite of infected female Anopheles. Malarial Parasite requires two hosts to complete its life cycle-Human and Anopheles mosquito which also acts as a vector or a transmitting agent.

9. Shuffner’s dots are related to _________
a) Entamoeba histolytica
b) Mosquito
c) Red Blood Corpuscles
d) Liver
Answer: c
Clarification: Shuffner’s dots are related to the Red Blood Corpuscles of humans. They are present in the cytoplasm of RBCs. Presence of these granules indicates that RBCs are infected with Plasmodium.

10. When can malarial parasite be obtained in RBCs of a patient?
a) When there is a sudden increase in pulse rate
b) When the temperature rises with rigour
c) When the temperature of a patient suddenly drops
d) When a patient experiences shortness of breath
Answer: b
Clarification: Malarial Parasite can be obtained in the RBCs of the patient when the temperature of the patient rises with rigour. The high temperature of the patient signifies that the RBCs have ruptured and have released Haemozoin toxin in the blood which is responsible for high temperature after every 48 hours with chills and shivering, followed by profuse sweating.

11. Which of the following fish is introduced in a pond to control or eliminate the vector responsible for the transmission of malaria and elephantiasis?
a) Chimaera
b) Scoliodon
c) Gambusia
d) Trygon
Answer: c
Clarification: For diseases such as Malaria and Elephantiasis that are transmitted through vectors, the most important measure is to control or eliminate the vectors and their breeding places. Therefore, fishes like Gambusia are introduced in ponds which feed on mosquito larvae.

12. Where does the sexual stage of Plasmodium gets completed?
a) In the RBCs of human
b) In the liver of human
c) In the salivary glands of the mosquito
d) In mosquito’s gut
Answer: d
Clarification: When the Anopheles mosquito sucks the blood of an individual infected with Plasmodium pathogen then all the stages of Plasmodium are digested except that of Macrogametocytes and Microgametocytes. Further, fertilisation and development take place inside mosquito’s gut.

13. Malignant tertian/subtertian fever is produced by _________
a) Plasmodium ovale
b) Plasmodium falciparum
c) Plasmodium vivax
d) Plasmodium knowlesi
Answer: b
Clarification: Malignant tertian/subtertian fever is produced by Plasmodium falciparum. This pathogen is the deadliest of all the Plasmodium species. It also causes cerebral malaria and persistent subclinical malaria.

14. Sporozoite stage of Plasmodium is the infective stage to the mosquito.
a) True
b) False
Answer: b
Clarification: Gametocyte stage of Plasmodium is infective to the mosquito. Sporozoite stage of Plasmodium is infective to Humans.

15. Chloroquine is given to treat which disease?
a) Malaria
b) Tetanus
c) Tuberculosis
d) AIDS
Answer: a
Clarification: Chloroquine is mainly given to treat malaria. Some other drugs like Quinine (from the bark of Cinchona), camaquine, primaquine and daraprim are also administered to control malaria.

Biology Aptitude Test for NEET Exam on “Human Disease – AIDS-2”.

1. How many HIV infected patients are believed to be present in India?
a) 1 million
b) 2.4 million
c) 3.8 million
d) 0.2 million
Answer: b
Clarification: NACO through its 1200 nationwide sentinel surveillance sites believe that the number of HIV infected patients in India was 2.4 million at the end of 2009, out of the total 33 million present to be worldwide. 63% of the HIV infected individuals lived in Andhra Pradesh, Tamil Nadu, Karnataka and Maharashtra.

2. Group of people with a high risk of contracting HIV infection are children below 5 years of age.
a) True
b) False
Answer: b
Clarification: Group of people with a high risk of contracting HIV infection include prostitutes, drug addicts, homosexual males, people with extramarital relations and recipients of unscreened blood transfusions.

3. Which of the following options is wrongly labelled in the diagram?

a) Two double-stranded RNA filaments
b) Glycoprotein pedicel
c) P-24 (capsid)
d) Lipid membrane
Answer: a
Clarification: The viral envelope encloses the RNA genome which is single-stranded RNA filament, segmented into two identical filaments and associated with a reverse transcriptase enzyme. The correct labelled diagram is as follows: