Molecular Basis of Inheritance focuses on the comprehensive and detailed study of not just the genes, but also heredity and genetic variations. It is keen on exploring why exactly do the children look similar to their parents and other related people, by researching on the DNA, RNA, and genetic code. These three are, in fact, the base of the molecular basis of inheritance, helping to smoothly facilitate the transferring of the genes from the parents to their children; the cycle then goes on from generation to generation.

• Molecular Basis of Inheritance is the sub-topic of Genetics & Evolution and has a weightage of around 8 to 9% in the exam. 
• Expected Questions to be asked on this topic are about five. Most of them will demand a comprehensive view of the topic as well as the sub-topics.

While there are other more important topics in the syllabus that students probably have to pay more attention to as well but this topic is also the most important in the biology section of NEET 2021 and should be studied and looked into thoroughly.

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Deoxyribonucleic Acid - DNA

The full-form of DNA is Deoxyribose Nucleic Acid and is present in the human body as a double-helical structure. 

• It is sort of a permanent home to all of the genetic information of that body. It is present in the nucleus of the cells as an acidic substance, as identified and researched by Friedrich Meischer in 1869. 
• Whereas, Watson and Crick provided us with the double-helical structure of the DNA.
• The parent DNA replicates itself in the daughter strands, which are then become the parent DNA in the next generation – the cycle then goes on as far as anyone is concerned.
• The length of the DNA depends on the number of nucleotide pairs present in it.
• Bacteriophage lambda has 48,502 base pairs.

Sample question

Question: The reason behind the antiparallel strand of DNA is

1. Hydrogen bond
2. Ionic bond
3. Phosphodiester bond
4. Disulphide bond

Solution – (a)

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Central Dogma

The Central dogma, first put forth by Crick, is the state where the DNA transforms into RNA, whereas RNA is converted into proteins. When it comes to retroviruses, however, this flow is actually reversed, with RNA becoming DNA and mRNA converting to Protein.

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DNA Packaging and DNA Replication

• DNA Packaging is the process where the negatively charged DNA comes in a package amidst the surrounding positively charged histone octamer. 
• The result of this is the birth of the structure called nucleosome.
• As for the DNA Replication, it is a well-known fact that DNA is efficient and can replicate itself easily.
• DNA actually goes through a semi-conservative replication, where two strands of DNA are formed, one being the same to one of the strands while the other one is complementary to the parent.

Sample question

Question: What is the nature of the strands of the DNA duplex?

1. Anti-parallel and complementary
2. Identical and complementary
3. Anti-parallel and non-complementary
4. Dissimilar and non-complementary

Solution - (b)

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Ribonucleic acid - RNA

RNA, on the other hand, is Ribonucleic acid and is an essential molecule, present as a long chain of nucleotides. 

• Existing as the first genetic material, the chain of RNA is made up of phosphate, nitrogenous bas and a ribose sugar. 
• It is nothing but a catalyst of the process and acts as the genetic material. RNA is present in the human body in two types, i.e. genetic and non-genetic.Genetic­ and non-genetic RNA only differs on one point–the latter one doesn’t function as a genetic material but as a protein synthesis and is further divided into three types, i.e. messenger, ribosomal and transfer.

Sample question

Question: Genetic information is transferred from nucleus to cytoplasm through

1. RNA
2. Anticodon
3. DNA
4. Lysosomes

Solution - (a)

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Genetic Code

The Genetic Code is a set of rules put forth by the body where the information stored in genetic materials (viz, the genetic type of RNA) is allowed to translate and transform into proteins by the living cells. 

• This genetic code lays down the rules of how codons are supposed to specify the amino acids that will be added on the time of the next protein synthesis. 
• It can simply be defined as the relationship between the amino acids sequence in the nucleotide chain of mRNA – or DNA –and the polypeptide chain amino acids. 
• Some features of the genetic code include - Degeneracy of genetic code;Triplet in nature; Comma-less; Non-ambiguous; Universality; Non-overlapping.

Sample question

Question: The anticodon of initiation codon for protein synthesis is -

1. UUU
2. AUG
3. UAC
4. CAU

Solution - (c)

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Quick Notes on Genome of Model organisms

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Difference between nucleotide and nucleoside

• The nucleic acid is a genetic material involved in the inheritance of information and present in the nucleus of a cell.
• It is made up of the three important ingredients- nitrogenous bases, sugar and phosphate.These threes are collectively referred to as a ‘nucleotide’.
• A nucleoside, however, is insignificant for a cell and doesn’t involve in constructing DNA. The nucleosides are only made up of nitrogenous bases and sugar. 
• The nucleoside is formed by the hydrolysis of nucleotides. Through hydrolysis, the nucleotides are converted into nucleosides while through the process of phosphorylation, the nucleosides are converted into nucleotides.

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Important topics in Molecular Basis of Inheritance

It is not a new thing to see that Molecular Basis of Inheritance is not only a vast topic but also has several topics, out of which some are more important than others. While it is advisable that students should study about everything under it, there are some of the sub-topics, which are important enough to give them little more than the usual importance -

1. DNA
2. Structure of a polynucleotide chain
3. Double Helix Model for Structure of DNA
4. Experiment of F. Griffith
5. Experiment of Hershey & Chase
6. Experiment of Meselson & Stahl
7. Transcription
8. Genetic Code
9. Genetic Mutation
10. Genetic Code on Operon Theory
11. Mechanism – Replication
12. Mechanism - Transcription
13. Mechanism –Translation
14. The Lac Operon

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Previous Years Solved Sample Questions on Molecular Basis of Inheritance

1. Question: Central dogma or Information flow of modem biology is:

A) RNA → Proteins → DNA.

B) DNA → RNA → Proteins.

C) RNA → DNA → Proteins.

D) DNA → RNA → Proteins.

Solution: (D)

2. Question: AUG initiation codon occurs over:

A) 3'end of mRNA

B) 5'end of m RNA

C) Short arm of t RNA

D) long arm of t RNA

Solution: (B)

3. Question: When here is a nonsense mutation in the lac Y gene then enzymes will be produced in a cell?

A) Lactose Permease

B) Transacetylase

C) Lactose permease and transacetylase

D) β-galactosidase

Solution: (D)

4. Question: What was the key finding of the Hershey and Chase experiments on the mechanism of viral replication?

A) Protein, not DNA, is the hereditary material.

B) DNA, not protein, is the hereditary material.

C) DNA and Protein play an equal role in determining inheritance.

D) Neither DNA nor Protein play a role in determining inheritance.

Solution: (B)

5. Question: What will be the percentage of adenine if a double-stranded DNA has 20% of cytosine?

A) 20%

B) 40%

C) 30%

D) 60%

Solution: (C)

Download NEET Practice Papers

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Some Tips to Solve Questions

1. Attempting the easy questions first: Easy questions should be attempted as soon as possible. Just because they are easy, don’t neglect them. It might happen that you waste all your time on difficult questions and now there is no time left to solve the easy ones.
2. Avoid negative marking: If you don’t know any answer and are positive you won’t be able to remember it, don’t solve it, so that you don’t get negative marking otherwise. No marking is better than negative marking.
3. Keep a steady head: Panicking won’t lead you anywhere. Just keep a calm head and dive in the paper. You will notice how important it is to be calm during such an important exam – it will definitely score you some good grades.

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How to prepare for NEET Biology section?

Biology section carries most of the marks – 90 marks, with 45 for Botany and 45 for Zoology – meaning that there are definitely a greater number of questions to be asked in this section, and most of them are probably on Molecular Basis of Inheritance. In order to tackle this, students are advised to be prepared with a comprehensive study plan, which will not only get the deserved attention to the Biology section but also spare enough time for the Physics and Chemistry section. Also Read NEET Biology Topic Wise Preparation Tips

1. Make flashcards: Biology terms are hard to remember, sometimes even more than mathematics formula. This is where flashcards could help a lot. Incorporate them in your study timetable for the biology section and you will not have any problem remembering the important pointers.
2. Study eagerly: Don’t just study for the sake of it. Take a real interest in whatever is in front of you. Passive studying will take you nowhere; actively seeking knowledge will.
3. Solve previous years' papers: There are more than enough papers online and not to forget the papers that you would be provided by your tuitions and classes. Solve them once, and then once done, solve them again. The practice is the key.
4. Best Books: Prefer the best study material. Some of the best books are mentioned below in the table: 

These books will help you to sail through the Biology section smoothly and without any hassle.