List of top Questions asked in CBSE CLASS XII

Draw a schematic diagram of the \textit{E.coli vector pBR 322 and mark the following in it:}
(a) ori
(b) rop
(c) ampicillin resistant gene
(d) tetracycline-resistant gene
(e) restriction site Bam HI
(f) restriction site EcoRI

Explain brood parasitism with the help of a suitable example.

Assertion (A): Some aquatic ecosystems have inverted biomass pyramids.
Reason (R): More energy is required by the organisms occupying higher trophic levels.

Explain the improvement in the quality of the milk produced by it.

Study the graph given below that represents the changes in the thickening of the uterine wall in women ‘X’ and women ‘Y’ over a period of one month: \textit{(Refer to the provided graph.)}
What does the graph with respect to woman ‘X’ and woman ‘Y’ indicate? Give a suitable reason.

Name the first developed transgenic cow.

Assertion (A): A given fig species can be pollinated only by its partner wasp.
Reason (R): The wasp pollinates the fig inflorescence while searching for suitable egg-laying sites.

Assertion (A): Patents are granted by the government to an inventor.
Reason (R): Patents prevent others from commercial use of an invention.

Assertion (A): Plasmids are autonomously replicating circular extra-chromosomal DNA.
Reason (R): Plasmids are usually present in eukaryotic cells.

The commonly used vector for human genome sequencing was/were:

The ‘molecular scissors’ fall in the category of:

Select the option that gives the correct identification of ovum, morula, and blastocyst in a human female reproduction system as shown in the following diagram: \textit{(Refer to the provided diagram.)}

Turner’s syndrome in humans occurs due to:

ELISA technique is based on the principle of:

Study the table given below: \begin{center} \begin{tabular}{|c|l|l|} \hline Contraceptive & Mode of Action
\hline A. The pill & I. Prevent sperm reaching cervix
B. Condom & II. Prevent implantation
C. Vasectomy & III. Inhibits ovulation
D. Copper-T & IV. Semen contains no sperm
\hline \end{tabular} \end{center} Select the option where contraceptive/contraceptive method are correctly matched with their mode of action:

Study the following diagram of Transverse Section of a young anther of an angiosperm:
\textit{(Refer to the provided diagram)}
Select the option where parts ‘A’, ‘B’, and ‘C’ are correctly identified.

Hugo de Vries proposed the mutation theory of organic evolution after his experiments on:

Identify the category of genetic disorder depicted in the pedigree chart given below:

A list of organisms is given in column ‘R’, whereas in column ‘S’ a list of products produced by them: \begin{center} \begin{tabular}{|c|c|} \hline Column ‘R’ (Organisms) & Column ‘S’ (Products)
\hline \textit{Lactobacillus} & Cheese
\hline \textit{Saccharomyces cerevisiae} & Curd
\hline \textit{Aspergillus niger} & Citric acid
\hline \textit{Acetobacter aceti} & Acetic acid
\hline \end{tabular} \end{center} Select the option where the organisms are correctly matched with the product:

Which of the options has correct identification of ‘P’, ‘Q’, and ‘R’ in the illustration of ‘Central Dogma’ given below?

In a fertilized ovule of an angiosperm, the cells in which \(n\), \(2n\), and \(3n\) conditions respectively occur are:

Give the scientific name of the bacteria widely used in biotechnology to create a GM cotton crop resistant to bollworm attacks.

Explain any three roles of ‘predation’ in an ecosystem with the help of suitable examples.

Specific site at which meiosis II is completed.