List of top Biology Questions asked in CBSE CLASS XII

Given below is a list of some commercially important products in column A, whereas in column B are names of source organisms:
\[ \begin{array}{|l|l|} \hline \textbf{Column A (Bioactive Products)} & \textbf{Column B (Source Organisms)} \\ \hline A. \text{Cyclosporin – A} & i. \text{Streptococcus} \\ B. \text{Statins} & ii. \text{Trichoderma polysporum} \\ C. \text{Streptokinase} & iii. \text{Penicillium notatum} \\ D. \text{Penicillin} & iv. \text{Monascus purpureus} \\ \hline \end{array} \]

Select the option where the product and their source organisms are correctly matched.
How do the following organisms act as bio-fertilizers? Explain.
(a) Mycorrhiza
(b) Anabaena
(c) Rhizobium
Write the initiating codon for translation, its anticodon, and the amino acid it codes for.
Describe the different steps in the sexual mode of reproduction in the life cycle of a malarial parasite from the time of its initiation till where it is completed and ready to start a fresh cycle.}
Why is sickle-cell anaemia, a human blood disorder, so named?
Identify the polarity from ‘X’ to ‘Y’ in the mRNA segment shown. Mention how many more amino acids can be added to the polypeptide that is being translated and why.
Work out a cross to explain how normal parents may have a sickle-cell anaemic child.
Explain the charging of an adaptor molecule. Why does this molecule need to be charged?
Explain the genetic basis that results in the expression of this disorder.
Describe the life cycle of HIV from the time of its entry into the human body till full-blown AIDS sets in.
Write the symptoms of malaria in humans and explain what causes these symptoms.
‘A proper understanding of the menstrual cycle can help immensely in family planning.’ Do you agree with the statement? Provide reasons for your answer.
Growth curve ‘B’ shows a different pattern from that of growth curve ‘A’. Justify giving one reason.
Which of the two curves is relevant in present days with respect to human population in our country and why?
Draw a labelled diagram showing the different embryonic stages of a dicot plant, up to a fully mature embryo.
Which one of the two curves is more “realistic” and why?
Why does endosperm development precede embryo development in angiosperm seeds? State the role of endosperm in mature albuminous seeds.
Mention what does the dotted line in the graph indicate and state its importance also.
Write the number of RNA polymerases involved in the transcription of DNA in a prokaryote and eukaryotes.
Whose skulls ‘A’, ‘B’, and ‘C’ are shown below? Which of the two are more similar to each other?
Name this RNA product transcribed from the DNA that subsequently translates into a polypeptide of 400 amino acids. Mention the enzyme responsible for transcribing this type of RNA from the DNA.
Name the (i) ape-like (ii) man-like primates that existed 1.5 million years ago.
Name and explain the process the RNA molecule transcribed from 8000 nucleotide-long DNA undergoes to be able to translate a polypeptide of 400 amino acids.
Identify the growth curves ‘A’ and ‘B’.
Name the human body organ affected by the consumption of these drugs.