Xam Idea Class 12 Biology Chapter 6 Solutions: Molecular Basis Of Inheritance

Xam Idea Class 12 Biological Solutions for Chapter 6 ‘The molecular Basis of Inheritance’ are explicitly designed bearing in mind the challenges you can encounter when solving these problems in board exams. After practising these problems you will get a realistic picture of what DNA, genetic code, and gene expression is all about. Such methods can also enable you to grasp the principle of DNA synthesis, gene encoding, DNA fingerprinting, transcription, translation, gene regulation, and many more. Professionals in this field illustrate the answers to problems in an extremely simple way to incorporate all of the basic concepts/hypotheses and guidelines of biology.

Xam Idea Class 12 Biology Solutions for Molecular Basis Of Inheritance persist a total of 249 questions that are divided into four sections. They are very short answer types, short answer type questions (type I and II), and long answers type questions, respectively. All questions have been answered in quite a clear and concise manner in our Xam Idea solutions. You can quickly grasp and retain essential concepts of the molecular basis of inheritance over a prolonged period.

Xam Idea Solutions for Class 12 Molecular Basis of Inheritance by Instasolv have concise language as well as the exquisite descriptions of all concepts. These solutions offered by our learning expertise will help to ensure that you thoroughly understand these principles with instant approaches. Having the aid of our stepwise solutions will certainly help you overcome some barriers and ready yourself properly for any kind of examination. All our solutions are in synchronization with the latest CBSE Class 12 Biology syllabus.

Important topics of Xam Idea Class 12 Biology Solutions Chapter 6: Molecular Basis Of Inheritance


  • Long-chain polymer composed of deoxyribonucleotides.
  • DNA length relied on the number of nucleotide pairs that appear within it.
  • Bacteriophage lambda contains 48,502 total base pairs.


  • First genetic material.
  • RNA is a non-hereditary nucleic acid apart from certain viruses (retroviruses).
  • RNA behaves as both a genetic material as well as a catalytic material.
  • This is a ribonucleotide polymer that consists of pentose ribose sugar, phosphoric acid & nitrogen base (A, U, G, and C).
  • It can be of two forms, genetic & non-genetic.

Central Dogma

  • Crick suggested the term “central dogma”.
  • It says that genetic material is derived through DNA à RNA à Protein.
  • In a few viruses, such as retroviruses, the information flow is always in the opposite direction from RNA à DNA à mRNA à Protein.

Structure of Polynucleotide Chain

Three Components of a Nucleotide

  • They are Nitrogen base, pentose sugar (ribose in RNA and deoxyribose in DNA) and Phosphoric acid. Nitrogen bases are of 2 types: Purines (Adenine and Guanine) and Pyrimidines (Cytosine, Uracil, and Thymine)
  • Adenine, Guanine, and Cytosine are the same both in RNA and DNA. Uracil only appears in RNA whereas, DNA contains “Thymine” instead.
  • RNA has Pentose sugar and ribose whereas DNA has Deoxyribose sugar.
  • Two nucleotides merged by 3’-5’ Phosphodiester bond linkage that forms dinucleotide.
  • Both strands of DNA are said to be DNA duplexes that are antiparallel to each other as well as complementary in nature (5’->3’ direction and 3”->5” direction).

DNA History

  • It is an acidic substance inside the nucleus.
  • Firstly coined by Friedrich Meischer in 1869 as ‘Nuclein”.
  • Double helix structure of DNA in 1953 discovered by James Watson and Francis Crick, based on X-ray diffraction pattern as developed by Maurice Wilkins and Rosalind Franklin.

Organizing DNA of Eukaryotes

Essential proteins or histones have been positively labelled (strong and specific owing to the inclusion of strong and specific amino acid sequences, lysine, and arginine).

  • Histone octamer-A group of 8 molecules of histone.DNA (charged negatively) 
  • Gusts around an octamer of histone (positively charged) to create a nucleosome.
  • 1 nucleosome is approximately 200 bp DNA.

DNA Replication

DNA replication is the mechanism by which DNA creates a duplicate of its own throughout cell division.

Delbruck coined 3 methods of replication of DNA. They are Dispersive, Conservative and Semi-conservative.

Genetic Code

  • The word genetic code has been provided by George Gamow (1954). It was him who first suggested a triplet code (one codon composed of 3 nitrogen bases).
  • It is an association between the series of amino acids within a polypeptide chain and the DNA or mRNA nucleotide sequence. 
  • A codon is said to be a nucleotide sequence throughout mRNA which codes for specific amino acids; while the genetic code seems to be the nucleotide sequence within mRNA molecules that provides data for polypeptide chain synthesis. 
  • The encoding for just 20 amino acids is 61 out of 64 codons.
  • The biggest issue with the genetic code was to identify the precise number of nucleotides within the codon that also codes for an amino acid.
  • Non-histone chromosomal proteins-Additional collection of proteins needed for chromatin packing at the highest level.

Griffith’s Experiment

  • Principle of Transformation:

Griffith conducted tests containing Streptococcus pneumonia bacteria. This bacterium does have two strains − the strain S as well as the strain R.

  • Live R strain throughout the vicinity of heat-killed S strain induces infectivity since somewhere R strain bacteria are converted via temperature-killed S strain bacteria. It was therefore assumed that there would be a transition of genetic information.
  • The method by which DNA is converted to RNA is termed as RNA transcription, and the process through which RNA is being used to make proteins is known as translation.

Genomics and Human Genome Project

  • The partnership deal between the US Department of Energy and the National Institute of Health (NIH); later joined by Wellcome Trust (UK).
  • Launched in 1990 and completed in 2003.
  • This project has worked for the creation of a full human DNA series.

Perspectives and consequences of the human genome:

  • The genome experiment is being contrasted with the development of antibiotics.
  • Efforts are underway to identify genes that will return cancerous cells to normal.

DNA Fingerprinting

DNA fingerprinting is indeed a process used to determine a person from a DNA sample by taking a look at varying thicknesses within their DNA.

Applications of DNA Fingerprinting

  • Criminal identification within a forensic laboratory.
  • Arbitration of inheritance issues.
  • Check that a prospective applicant is, as he or she claims, truly a near relative of a current citizen.
  • Classify racial groups to rewrite biological evolution.

Discussion of exercises of Xam Idea Class 12 Biological Solutions Chapter 6: The Molecular Basis of Inheritance

As mentioned earlier, Xam Idea  Class 12 Biological Solutions Chapter 6. The molecular basis of inheritance contains 249 questions in total which are divided into four categories and further into PYQ (past years questions) and OIQ (objective inventory questionnaires).

Very Short Answer Questions

  • It comprises a total of 76 problems out of which 31 problems placed under the PYQ segment and the rest 45 problems placed under the OIQ segment. 
  • These questions are normally straightforward and simple to answer. This section is based on gel electrophoresis, hnRNA, splicing, and central dogma.

Short Answer Questions Type – I

  • This section essentially contains 64 questions that are categorized into 50 PYQ and rest 14 problems within the OIQ segment.  
  • You are required to present a neat diagrammatic representation to support your answers whenever required.
  • The questions are based on the structure of DNA, RNA, and tRNA.

Short Answer Questions Type – II

  • This section essentially contains 42 questions that are categorized into 23 PYQ and rest 19 problems within the OIQ segment.  
  • Here you need to analyze the gene regulation mechanism of DNA.

Long Answer Type Questions

  • This section contains 67 questions that are segmented into 48 questions in PYQ and 19 problems within the OIQ segment.
  • Topics covered in this section are DNA replication, translation, and transcription.

Why Use Xam Idea Class 12 Biological Solutions Chapter 6: The Molecular Basis of Inheritance by instasolv?

  • Xam Idea solutions created by our subject after experts will help you to predict the kinds of questions that can be asked in CBSE Class 12 board exams. 
  • To achieve a decent view of the topics, our approach is split into various sections of the examination.
  • Our Xam Idea Solutions are error-free available on our website for free of cost.
  • Instasolv solutions are very well-organized and in sync with the latest CBSE syllabus for Class 12.