Science (English Medium) इयत्ता १२ - CBSE Important Questions for Biology

The human chromosome with the highest and least number of genes in them are respectively ______.

Which of the following amino acid residues will constitute the histone core?

(a) Identify the polarity of x to x’ in the diagram below and mention how many more amino acids are expected to be added to this polypeptide chain.

(b) Mention the codon and anticodon for alanine.

(c) Why are some untranslated sequences of bases seen in mRNA coding for a polypeptide? Where exactly are they present on mRNA?

Observe the segment of mRNA given below.

(a) Explain and illustrate the steps involved to make fully processed hnRNA?

(b) Gene encoding RNA Polymerase I and III have been affected by mutation in a cell. Explain its impact on the synthesis of a polypeptide, stating the reasons.

How does initiation of the translation process occur in prokaryotes? Explain.

Where are the untranslated regions located on mRNA and why?

Explain the process of binding of ribosomal units to mRNA during protein synthesis.

A short piece of DNA, having 20 base pairs, was analyzed to find the number of nucleotide bases in each of the polynucleotide strands. Some of the results are shown in the table.

How many nucleotides containing Adenine were present in strand 2?

What is the smallest part of a DNA molecule that can be changed by a point mutation?

• 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.

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.