Science (English Medium) Class 12 - CBSE Important Questions for Biology

• Assertion: Ribosomal RNA is synthesized in the nucleus of the cell.
• Reason: It is translated with the enzyme RNA polymerase III.

The image below shows the result of plating bacteria in a chromogenic medium after incorporating the gene of interest in the plasmid. Some plates had blue colonies; some plates had white colonies. A single bacterium extracted from Plate I, II, and III is shown below:

On the basis of your observations:

1. Identify the plate(s) which is/are white. Give a reason.
2. Identify the plate(s) which is/are blue. Give a reason.

Given below is a stretch of DNA showing the coding strand of a structural gene of a transcription unit?

5’-ATG ACC GTA TTT TCT GTA GTG CCC GTA CTT CAG GCA TAA-3’

1. Write the corresponding template strand and the mRNA strand that will be transcribed, along with its polarity.
2. If GUA of the transcribed mRNA is an intron, depict the sequence involved in the formation of mRNA/the mature processed hnRNA strand.
   i. In a bacterium
   ii. In humans
3. Upon translation, how many amino acids will the resulting polypeptide have? Justify.

Write the probable differences in eating habits of Homo habilis and Homo erectus.

Explain co-evolution with reference to parasites and their hosts.

How did Darwin explain adaptive radiation ? Give another example exhibiting adaptive radiation.

Why are analogous structures a result of convergent evolution?

Cite an example where more than one adaptive radiations have occurred in an isolated geographical area. Name the type of evolution your example depicts and state why it is so named.

What role does an individual organism play as per Darwin's theory of natural selection?

Mention any four special adaptive evolved in parasites for their parasite mode of life.

Explain divergent evolution with two examples. 

Answer the following question.
Write two differences between Homo erectus and Homo habilis.

Write two differences between Homo erectus and Homo habilis

Answer the following question.
Write the characteristics of Ramapithecus, Dryopithecus, and Neanderthal man.

According to the Hardy-Weinberg principle, the allele frequency of a population remains constant. How do you interpret the change of frequency of alleles in a population?

How does the Hardy-Wienberg equation explain genetic equilibrium?

How is Hardy-Weinberg's expression “(p² + 2pq + q²) = 1” derived?

List any two factors that can disturb the genetic equilibrium.

At a particular locus, the frequency of allele A is 0.8, and that of allele a is 0.2. What would be the frequency of heterozygotes in a random mating population at equilibrium?

The graphs below show three types of natural selection. The shaded areas marked with arrows show the individuals in the population who are not selected. The dotted vertical lines show the statistical means.

character Graph A	character Graph B	character Graph C

1. What names are given to the types of selection shown in graphs A, B and C?
2. After the selection has operated for several generations in the above populations indicated as, Graph A, B and C, graphically illustrate the probable results.