Important Notes on Molecular Basis of Inheritance for NEET Biology


Simplifying NEET Preparation Using the Molecular Basis of Inheritance

Biology is the primary subject in NEET, which is why your preparations must be perfect for its various topics. Following the important notes of biology for NEET molecular basis of inheritance is crucial when it comes to understanding the basics of DNA and RNA. Basically, this topic highlights how certain characteristics are passed from generation to generation among human beings.

However, before proceeding to the molecular basis of inheritance NEET notes, let us learn a bit more about nucleotide, RNA and DNA, including the basic difference between the latter two.

Biology is the primary subject in NEET, so your preparations for its various topics must be flawless. When it comes to understanding the fundamentals of DNA and RNA, it is critical to follow the important notes of biology for NEET molecular basis of inheritance. Essentially, this topic focuses on how certain characteristics are passed down from generation to generation among humans.

However, before we move on to the molecular basis of inheritance NEET notes, let us first learn a little more about nucleotides, RNA, and DNA, as well as the fundamental difference between the latter two.

What are RNA and DNA?

RNA (Ribonucleic Acid) and DNA (Deoxyribonucleic Acid) are the two primary building blocks. Both of these act as a store for genetic materials, although DNA is more common. Listed below are some of the differences between DNA and RNA, which can promote better understanding of them.



DNA contains 2-deoxy-D- ribose sugars.

RNA contains D- (-)- ribose sugars.

Characterised by a double alpha-helix structure.

Characterised by a single alpha-helix structure.

DNA is responsible for hereditary transmission effects.

Protein synthesis depends on RNA.

Thymine and cytosine form pyrimidine bases, while adenine and guanine make up purine bases. 

While guanine and adenine form purine bases in RNA as well, it contains uracil pyrimidine and cytosine as well.

DNA carries replication properties.

RNA lacks any facility for replication.

DNA molecules are large. 

RNA molecules, on the other hand, are comparatively much smaller.

The two primary building blocks are RNA (ribonucleic acid) and DNA (deoxyribonucleic acid). Both of these serve as a repository for genetic materials, with DNA being the most common. Some of the differences between DNA and RNA are listed below to help you understand them better.

DNA’s Double Helix Structure

The Important notes of biology for NEET molecular basis of inheritance are incomplete without a reference to the characteristics of the double-helix model for DNA. Here is what you need to know about it.

  • Crick and Watson were the two scientists who proposed this revolutionary double helix model for DNA in 1953. 

  • Later, scientist Ervin Chagraff postulated that the ratio of Cytosine and Guanine to Thymine and Adenine is always constant, and is equal to one.

  • DNA contains two polypeptide chains, with opposing polarity.

  • The nitrogen base of each chain combines with hydrogen to form the base pair or bp.

  • Pyrimidine base of one nucleotide chain always maintains a connection with the purine base chain of another nucleotide.

  • Similarly, Thymine always links with Adenine only.

DNA Replication

Molecular basis of inheritance class 12 notes rightly explains that DNA replication is a process by which genetic materials from nucleic acid compounds are transferred into proteins. The amount of genetic data through such replication remains constant between the parent and progeny cells after mitosis.

The class 12 notes on the molecular basis of inheritance correctly explain that DNA replication is a process by which genetic materials are replicated.

Some of its Features Include

  • Replication origin is the source from which this process begins.

  • Deoxyribonucleoside triphosphate performs two vital functions here, namely, it acts as a substrate and it provides energy for the polymerisation to occur.

  • The DNA structure undergoes a mild change, leading to the formation of a replication fork. This acts as a site for replication.

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The above diagram shows the process of replication occurring in DNA. Studying the same should help you understand this procedure easily.

DNA Transcription

Transcription is the process during which information from the DNA is transferred to the RNA. However, only a single segment from the former is transferred. Here are some salient features of transcription – 

  • DNA transcription involves three regions, namely, a terminator, a structural gene and a promoter.

  • Keep in mind that in RNA, Adenine cannot pair with Thymine, but instead links with Uracil.

  • Transcription process in bacteria is quite distinct from transcription in other living organisms. For bacteria, mRNA cytosol and nucleus are fused together, which means that there is no need for further processing. 

Differences Between RNA Transcription and DNA Replication

The distinction between DNA replication and RNA transcription is one of the important biology notes for the NEET molecular basis of inheritance. The table below contains all of the pertinent information in this regard.

RNA Transcription

DNA Replication

Based on the need, small portion of DNA is transcribed

The replication happens to the entire chromosome and not just a part

The enzyme involved in the process is RNA polymerase 

The necessary enzyme for the replication is DNA polymerase

A single stranded RNA molecule is created

Two double stranded DNA molecules are formed

Adenine on DNA strands fuses with Uracil created on the RNA strand

Adenine on strand mixes with Thymine on the formed DNA strand

Aside from replication and transcription, cells also translate. Translation is the method by which amino acid polymerisation takes place. All three RNAs, tRNA, mRNA, and rRNA, play critical roles in the translation process.

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FAQs (Frequently Asked Questions)

1. What is Molecular Biology's Central Dogma?

The flow of genetic information from DNA to RNA, and then to proteins, is referred to as Central Dogma. As a result, in molecular biology, this protein is known as the Central Dogma. Francis Crick was the first scientist to propose such a theory.

2. What Does Frameshift Mutation Mean?

Any unanticipated gain or loss in one or two base pairs alters the reading frame. A frameshift mutation is the name given to this phenomenon.

3. When and why did the Human Genome Project begin?

To know the answer for the same visit Vedantu. Download free study material from on NCERT, CBSE, ICSE, IIT, JEE, Engineering and medical entrance exam materials in pdf format. 

4. Why is there a break in the synthesis of DNA on one of the parental strands?

The biological process of DNA synthesis occurs in the 5′ to 3′ direction naturally. The strands of double-stranded DNA are parallel and antiparallel to each other. During DNA synthesis, both strands serve as templates, and only one (3′ to 5′ direction) can synthesize the parallel strand in the 5'3′ direction. The other strand, 5′ to 3′, is synthesized in the opposite direction, resulting in Okazaki fragments, which are short stretches of DNA. This is the cause of the sporadic synthesis of DNA on one of the parental strands.

5. Explain the DNA fingerprinting procedure.

DNA fingerprinting is a technique for analyzing the genetic makeup of living things. It is commonly used in forensic tests and paternity tests to identify the biological parents of a child, as well as to identify the criminal during forensic investigations.