The Central Board of Secondary Education (CBSE) will conduct the board exam for Class 12 Biology paper on March 19, 2024. Students appearing in the boards can visit the official website of the CBSE to check question papers of the previous years to familiarise themselves with the paper pattern. Question papers are available from the board year 2019 on the official website of the CBSE.
Important High Marks Questions From Previous Year Paper
Q) What is the chemical name of 'smack'? Why is the consumption of smack considered as an abuse?
(ii) Name the source plant and one effect of the following drugs on the human body :
(1) Marijuana (2) Cocaine (3) Morphine
Q)A time-bound vaccination programme is followed for the children in our country from their birth up to ten years of age. A graph plotted shows the effect of the vaccination followed by infection by the same pathogen, and the antibody concentration in the blood of the child.
Q)Explain why the administration of a vaccine causes an increase in the antibody concentration.
Q)A true breeding tall pea plant with round seeds is crossed with a recessive dwarf pea plant having wrinkled seeds. Work out the cross up to F2 generation giving the phenotypic ratios of F1 and F2 generation respectively.
(ii) State the Mendelian principle that can be derived only with the help of such a cross.
Q) Meselson and Stahl carried out an experiment to prove the nature of DNA replication. Recall the experiment and answer the following questions.
(i) Which two types of nitrogen were used by them in their experiment and why ?
(ii) Why did they take samples of E. coli at definite time intervals for their observation ?
(iii) State the role of caesium chloride density gradient in their experiment.
(iv) Write the conclusions they arrived at.
Q) Gene expresses itself in a cell system as a protein/enzyme. How does an expression of gene occur in a cell system and when does it need to occur, and how the gene expression is regulated in a prokaryote cell system was studied by the combined efforts of Jacque Monod, the biochemist and Francois Jacob, the geneticist. For their work on lactose metabolism in E. coli a lac they were awarded the Nobel Prize in 1965.
(a) Why is lac operon said to be a transcriptionally regulated system ? 1
(b) It is said that the lac operon has to be operational at a very low level in the bacterial cell all the time. Justify.
(c) Why is the regulator gene in lac ?
(d) Draw a schematic diagram of lac operon in absence of inducer in the culture medium of the bacteria.
Q) Draw a schematic diagram of lac operon in the presence of inducer in the culture medium of the bacteria.
Q) Expand the abbreviations given below, used for different modes of assisted reproductive technologies :
(1) ZIFT
(2) ICSI
(3) IUT
(4) GIFT
(ii) Which one of them cannot be considered as a procedure of IVF ? Give reasons in support of your answer.
Q) Differentiate between the following :
(i) Perisperm and Pericarp
(ii) Syncarpous pistil and Apocarpous pistil
(iii) Plumule and Radicle