List of top Biology Questions asked in CBSE CLASS XII

(a) Name any two copper releasing intra-uterine devices. State two reasons that make them effective contraceptives.
(b) Name any two outbreeding devices that flowering plants have developed and explain how they help in encouraging cross-pollination.

Although Hemophilia and sickle cell anemia are two blood-related Mendelian disorders, yet they differ in their pattern of inheritance. State any two differences.

Assertion (A): Loss of biodiversity can occur due to overexploitation of resources.
Reason (R): Introduction of Clarias gariepinus in Indian rivers has led to a decline in native Indian fishes.

Assertion (A): Specific enzymes are used to degrade the cell wall in organisms to isolate the DNA from the cell.
Reason (R): Fungal cell wall is degraded by the enzyme cellulase.

Assertion (A): RNA is unstable and can mutate at a faster rate.
Reason (R): The presence of 2’-OH group in every nucleotide of RNA makes it labile and easily degradable.

Assertion (A): Virus-infected cells produce interferons.
Reason (R): Interferons can cause inflammation of virus-infected cells.

The pyramid of biomass in the sea is generally inverted because in the sea:

A woman with normal vision has a colour blind father. She marries a man with normal vision. The percentage chance of their progeny being colour blind is:

The vector for dengue fever is:

Which one of the following is not a feature of plasmids?

Which one of the following pairs is not correctly matched?

In a ’transcription unit’, the ’terminator’ is located towards the:

In the double helical structure of DNA molecule, the strands are:

A population is in genetic equilibrium/Hardy-Weinberg equilibrium for a gene with 2 alleles (dominant allele is ‘A’ and recessive allele ‘a’). If the frequency of allele ‘A’ is 0.6, then the frequency of genotype ‘Aa’ is:

Which one of the following statements is not true?

In humans, the secondary oocyte completes meiotic division when:

An angiosperm embryo sac is located within the:

Select the \(\textit{incorrect}\) match from the following:
 

The type of bond represented by the dotted line ‘-----’ in a schematic polynucleotide chain is: 

Identify A, B, C, D, E, and F in the table given below: 

In a family, the father, the daughter, and the son are colour blind, whereas the mother has normal vision. Do you think the son and daughter have inherited the disease from their father? Work out a cross to justify your answer.

What are transgenic animals?

Name the first transgenic cow and state its importance.