List of top Biology Questions on Molecular Basis of Inheritance asked in CBSE CLASS XII

Regulation of lac operon by repressor is referred to as:

Explain how the addition of lactose in the medium regulates the switching on of the lac operon in bacteria.

Study the given molecular structure of double-stranded polynucleotide chain of DNA and answer the questions that follow.

(a) How many phosphodiester bonds are present in the given double-stranded polynucleotide chain? 
(b) How many base pairs are there in each helical turn of double helix structure of DNA? Also write the distance between a base pair in a helix. 
(c) In addition to H-bonds, what confers additional stability to the helical structure of DNA?

The process of copying the genetic information from one strand of DNA into RNA is termed as transcription. The principle of complementarity of bases governs the process of transcription, also except that uracil comes in place of thymine.
Study the complete transcription unit given below and answer the following questions: 

(a) Name the main enzyme involved in the process of transcription. 
(b) Identify coding strand and template strand of DNA in the transcription unit. 
Attempt either sub-part (c) or (d): 
(c) Identify (C) and (D) in the diagram, mention their significance in the process of transcription. 
OR 
(d) Describe the location of (C) and (D) in the transcription unit.} 
 

Given below is a heterogeneous RNA formed during Eukaryotic transcription:
 
How many introns and exons respectively are present in the hnRNA?

Use the given information to select the amino acid attached to the 3′ end of tRNA during the process of translation, if the coding strand of the structural gene being transcribed has the nucleotide sequence ‘TCC’.

Study the given below single strand of deoxyribonucleic acid depicted in the form of a “stick” diagram with 5′ – 3′ end directionality, sugars as vertical lines and bases as single letter abbreviations and answer the questions that follow.

Name the covalent bonds depicted as (a) and (b) in the form of slanting lines in the diagram.
How many purines are present in the given “stick” diagram?
Draw the chemical structure of the given polynucleotide chain of DNA.

Use the given information to select the amino acid attached to the 3′ end of tRNA during the process of translation, if the coding strand of the structural gene being transcribed has the nucleotide sequence TAC.