List of top Biology Questions asked in CBSE CLASS XII

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

Assertion (A): Linked genes do not show dihybrid F2 ratio 9 : 3 : 3 : 1. 
Reason (R): Linked genes do not undergo independent assortment. 
 

Identify A, B, C, and D in the table given below:
Identify A, B, C, and D in the table given below:
Select the \(\textit{incorrect}\) match from the following:
 44 + XXY
The type of bond represented by the dotted line ‘-----’ in a schematic polynucleotide chain is: 
type of bond represented by the dotted line
Identify A, B, C, D, E, and F in the table given below: 
Breathing difficulty, cough, and chest pai
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.
Explain the convention for naming EcoRI.
With the help of an illustration only, show the action of EcoRI on a DNA polynucleotide.
Explain how it is ensured that the orchid \(\textit{Ophrys is pollinated by a specific species of bee.} \)
 
Describe co-evolution with the help of this example.
Read the following passage and answer the questions that follow. 
Isn’t it incredible that India’s land area is only 2.4 percent of the world’s total land area whereas its share of the global species diversity is an impressive 8-1 percent! However, in these estimates of species, prokaryotes do not figure anywhere. Biologists are always keen on collecting data with respect to species diversity observed in different regions of the world. The data collected based on the survey conducted for species richness of groups of mammals in three different regions of the world is shown in the bar graph below.
2.4 percent of the world’s total land area

Why is the species richness maximum in Region III in the bar graph? 
 
Study the diagram given below that shows the steps involved in the procedure of selecting transformed bacteria and answer the questions that follow: 
transformed bacteria
 (a) Identify the colony that has got transformed. Justify your answer. 
 
Draw a labelled diagram of a three-celled male gametophyte.
Stability, as one of the properties of genetic material, was very evident in one of the very early experiments in genetics. Name the scientist and describe his experiment. State the conclusion he arrived at.

State the role of the following techniques in the detection and diagnosis of cancer:

All normal human cells have genes that may become cancerous under certain conditions. Name them and explain how.

Name and explain the property present in normal cells but lost in cancer cells.
Explain the significance of the experiment carried out by S.L. Miller. Name the scientists whose hypothesis prompted him to carry out this experiment.