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12th biology question paper with answers in english

Question papers

Biology (set-1)

Short answers question (with answers)                         2-Marks

For class 12th                                                                                 Number of questions-26

1. What is the function of Endosperm?
Ans:-This provides nutrition to embryo. Endosperm is formed due to double fertilization, when one male gamete fuses with secondary nucleus of embryosec then triploid endosperm is formed, which provides nutrient to developing embryo. It contains maternal and paternal chromosome.  

2. What is micropropagation.
Ans:-Method of producing thousands of plants through tissue culture is called. All plants formed through this method will be genetically identical, i.e., they are somaclones. Many important food plant can be produced on commercial scale using this method.

3. What is double fertilization?
Ans:-After pollination, when pollen grain reaches to embryo sac it divides to form two male gametes, one male gamete fuses with egg cell to form zygote. It is called syngamy which develops into embryo and other male gamete fuses with secondary nucleus to form triploid primary endosperm cell. It is called triple fision which develops into endosperm.
            Hence in one embryo sac, two times fertilization takes place thus it is called double fertilization.  

4. Why vegetative reproduction is also considered as a type of asexual reproduction.
Ans:-Vegetative reproduction is also considered as asexual reproduction because, In vegetative reproduction production of offspring by one parent without the formation and fusion of gametes. The offspring receives all of their genetic material from one parent so both are identical to each other and are called as clone, Hence vegetative reproduction is also considered as asexual reproduction.

5. Define polyploidy.
Ans:-Polyploidy is the state of a cell or organism having more than two paired (homologous) sets of chromosomese. Polyploids are common among plants, as well as among certain groups of fish and amphibians.

6. What are multiple allelism ?
Ans:-Multiple allelism is the state when one contrasting characters is controlled by multiple alleles at a single genetic locus. It is called multiple allelism. E.g. blood group of human.

7. Give two main differences between DNA and RNA.
Ans:-
                       DNA
                      RNA
1. DNA is double stranded.
1. RNA is single stranded
2. DNA has nitrogenous bases adenine(A),guanine(G),cytosine(C),thymine(T)
2. RNA has nitrogenous bases adenine(A),guanine(G),cytocine(C),uracil(U)
3. DNA has deoxyribose sugar.
3. RNA has ribose sugar.

8. What are Okazaki fragments and what enzymes join them?
Ans:-During replication of DNA, replication takes place continuously on leading strand (5’-3’).But on lagging strand (3’-5’) replication takes place in fragments (discontinuous). This fragments of lagging strand is called Okazaki fragments. This fragments are joined by DNA ligase enzyme.  

9. Define Operon.
Ans:-A coordinating group of genes which are transcribe together and regulate a metabolic pathway as a unit, called operon. E.g.- Lac operon, tryptophan operon

10. What is transcription?
Ans:-Transcription is process of making of copy of genetic information stored in a DNA strand into a strand of mRNA. This process is induced by an enzyme RNA polymerase.

11. What are Penpide bonds?
Ans:-peptide bond is a chemical bond formed between two molecules when the carboxyl group of one amino acid reacts with the amino group of the other amino acid, releasing a molecule of water (H2O).

12. What do you mean by tissue culture?
Ans:-Tissue culture, a method of biological research in which fragments of tissue from an animal or plant are transferred to an artificial environment in which they can continue to survive and function. Thecultured tissue may consist of a single cell, a population of cells, or a whole or part of an organ.

13. Name some genetically engineered Crop plants.
Ans:-Golden Rice, Flavr Savr tomato, Bt cotton, Corn, Soybeans, Cotton, Alfalfa, Sugar Beets, Squash/Zucchini

14. What is apiculture and Sericulture?
Ans:-Apiculture: Beekeeping (or apiculture) is the maintenance of bee colonies, commonly in man-made hives, by humans.
Sericulture: Sericulture, the production of raw silk by means of raising caterpillars (larvae), particularly those of the domesticated silkworm (Bombyx mori).


15. What is special about Bacillus thuringensis?
Ans:-Bacillus thuringiensis (or Bt) is a Gram-positive, soil-dwelling bacterium, commonly used as a biological pesticide. During sporulation, many Bt strains produce crystal proteins (proteinaceous inclusions), called δ-endotoxins, that have insecticidal action. This has led to their use as insecticides, and more recently to genetically modified crops. 

16. What do you mean by Biopiracy?
Ans:-Biopiracy is the practice of commercially exploiting naturally occurring genetic material or biochemical. Without compensating the indigenous peoples or countries from which the material or relevant knowledge is obtained.

17. What is gene therapy?
Ans:-The introduction of normal genes into cells in place of missing or defective ones in order to correct genetic disorders is known as gene therapy.

18. What are vaccines?
Ans:-An antigenic substance prepared from the causative agent of a disease or a synthetic substitute, used to provide immunity against one or several diseases.

19. Name some antibiotics produced by micro-organisms.
Ans:- (a) PenicillinPenicillium chrysogenum
(b) CephalosporinCephalosporium acremonium
(c) ErythromycinStreptomyces erythreus
(d) StreptomycinStreptomyces griseus
(e) TetracyclineStreptomyces rimosus


20. What are the differences between transformation and transduction?
Ans:-
transformation
transduction
1. Direct uptake and incorporation of exogenous genetic material from its surroundings through the cell membrane  
1. Transfer of genetic material from donor to recipient bacteria through a bacteriophage.
2. Uses chemical transformation, electroporation, and particle bombardment.
1. Process whereby foreign DNA is introduced into another cell via a viral vector.


21. Give the name of four antibiotic producing organisms.
Ans:-Antibiotic producing organisms:
(a)Penicillium chrysogenum
(b)Cephalosporium acremonium
(c)Streptomyces erythreus
(d)Streptomyces griseus
(e)Streptomyces rimosus

22. What is retrovirus?
Ans:-retrovirus is a virus whose genes are encoded in RNA instead of DNA. Retroviruses use reverse transcriptase to transform their single-stranded RNA into double-stranded DNA.
e.g. – HIV

23. What is DNA probe?
Ans:-DNA probes are stretches of single-stranded DNA used to detect the presence of complementary nucleic acid sequences (target sequences) by hybridization. DNA probes are usually labelled, radioisotopes.

24. What is Symbiosis? Name two types of symbiosis.
Ans:-Interaction between two different organisms living in close physical association, typically to the advantage of both. e.g. – Mutualism, Commensalism


25. Name two types of ecological pyramid.
Ans:-Pyramid of number: – A “pyramid of numbers” shows graphically the population of each level in a food chain. It is an upright pyramid given in an ecosystem, where usually the producers are more in number than any other Trophic level. This shows the number of organisms in each trophic level without any consideration for their size.
Pyramid of energy: – An energy pyramid is a graphical model of energy flow in a community. 

26. What are the biotic components of ecosystem?
Ans:-There are three components of ecosystem:-
(a)Producers- Autotrophic organisms
(b)Consumers- Heterotophic organisms
(c)Decomposers- Microorganisms

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