Class 12th Biology 2012 Set1 Delhi Board Paper Solution

Section 1

Q1	Mention the unique flowering phenomenon exhibited by Strobilanthus kunthiana (neelakuranaji).
Q2	How does smoking tobacco in human lead to oxygen deficiency in their body?
Q3	A garden pea plant (A) produced inflated yellow pod, and another plant (B) of the same species produced constricted green pods. Identify the dominant traits.
Q4	Why is Eichhornia crassipes nicknamed as "Terror of Bengal"?
Q5	Write the location and function of the sertoli cells in humans.
Q6	Name the following: (a) The semi-dwarf variety of wheat is high-yielding and disease-resistant. (b) Any one inter-specific hybrid mammal.
Q7	Write the similarity between the wing of a butterfly and the wing of a bat. What do you infer from the above with reference to evolution?
Q8	Write what do phytophagous insects feed on.

Section 2

Q9	Draw a neat labeled sketch of a replicating fork of DNA.
Q10	(a) Highlight the role of thymus as a lymphoid organ. (b) Name the cells that are released from the above mentioned gland. Mention how they help in immunity.
Q11	Some organisms suspend their metabolic activities to survive in unfavourable conditions. Explain with the help of any four examples.
Q12	(a) State the role of DNA ligase in biotechnology. (b) What happens when Meloidegyne incognitia consumes cells with RNAi gene?
Q13	Why do clown fish and sea anemone pair up? What is this relationship called?
Q14	(a) Name the Protozoan parasite that causes amoebic dysentery in humans. (b) Mention two diagnostic symptoms of the disease. (c) How is this disease transmitted to others?
Q15	Name the plant source of the drug popularly called “smack”. How does it affect the body of the abuser ?
Q15	Why is Rhizobium categorized as a ‘symbiotic bacterium’ ? How does it act as a biofertiliser ?
Q16	(a) State the difference between meiocyte and gamete with respect to chromosome number. (b) Why is a whiptail lizard referred to as parthenogenetic?
Q17	Explain the work carried out by Cohen and Boyer that contributed immensely in biotechnology.
Q18	Where is sporopollenin present in plants? State its significance with reference to its chemical nature.

Section 3

Q19	It is established that RNA is the first genetic material. Explain giving three reasons. OR (a) Name the enzyme responsible for the transcription of tRNA and the amino acid the initiator tRNA gets linked with. (b) Explain the role of initiator tRNA in initiation of protein synthesis.
Q20	State the theory of Biogenesis. How does Millers experiment support this theory?
Q21	Name the two different categories of microbes naturally occurring in sewage water. Explain their role in cleaning sewage water into usable water.
Q22	Write the function of each one of the following: (a) (Oviducal) Fimbriae (b) Coleoptile (c) Oxytocin
Q23	Name the genes responsible for making Bt cotton plants resistant to bollworm attack. How do such plants attain resistance against bollworm attacks? Explain.
Q24	Study a part of the life cycle of malarial parasite given below. Answer the questions that follow: (a) Mention the roles of A in the life cycle of the malarial parasite. (b) Name the event C and the organ where this event occurs. (c) Identify the organ B and name the cells being released from it.
Q25	Given below is the representation of amino acid composition not the relevant translated portion of -chain of haemoglobin, related to the shape of human red blood cells. (a) Is this representation indicating a normal human or a sufferer from certain related genetic disease? Give reason in support of your answer. (b) What difference would be noticed in the phenotype of the normal and the sufferer related to this gene? (c) Who are likely to suffer more from the defect related to the gene represented the males, the females or both males and females equally? And why?
Q26	By the end of 2002 the public transport of Delhi switched over to a new fuel. Name the fuel. Why is this fuel considered better? Explain.
Q27	Draw a schematic sketch of pBR 322 plasmid and label the following in it: (a) Any two restriction sites. (b) Ori and rop genes. (c) An antibiotic resistant gene.

Section 4

Q28	Explain the carbon cycle with the help of a simplified model. OR Explain how does: (a) a primary succession start on a bare rock and reach a climax community? (b) the algal bloom eventually choke the water body in an industrial area?
Q29	The following is the illustration of the sequence of ovarian events (a - i) in a human female. (i) Identify the figure that illustrates ovulation and mention the stage of oogenesis it represents. (ii) Name the ovarian hormone and the pituitary hormone that have caused the above mentioned event. (iii) Explain the changes that occur in the uterus simultaneously in anticipation. (iv) Write the difference between c and h. (v) Draw a labeled sketch of the structure of a human ovum prior to fertilization. OR How does the megaspore mother cell develop into 7-celled, 8 nucleate embryo sac in an angiosperm? Draw a labeled diagram of a mature embryo sac.
Q30	What is the inheritance pattern observed in the size of starch grains and seed shape of Pisum sativum? Workout the monohybrid cross showing the above traits. How does this pattern of inheritance deviate from that of Mendelian law of dominance? OR State the aim and describe Messelson and Stahls experiment.