Important Notes on Molecular Basis of Inheritance for NEET Biology


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Molecular Basis of Inheritance: Simplifying NEET Preparation

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.

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.

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.

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.

(Image to be added soon)

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

A part of the important notes of biology for NEET molecular basis of inheritance is the distinction between DNA replication and RNA transcription. The table below provides all relevant information in this regard.

RNA Transcription

DNA Replication

Small portions of the DNA cell transcribed at a time, based on need. 

Replication occurs for the entire chromosome and not just a part. 

RNA polymerase is the enzyme involved in this process.

DNA polymerase is the enzyme necessary for this replication.

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

Adenine on a strand mixes with Thymine on the newly formed DNA strand.

One single-stranded RNA molecule is created.

Two double-stranded DNA molecules are formed.

Apart from the replication and transcription, cells also undergo translation. Translation is the process using which amino acid polymerisation occurs. All three RNAs, namely tRNA, mRNA and rRNA, perform crucial roles in this translation procedure. 

FAQ (Frequently Asked Questions)

1. What is Central Dogma in Molecular Biology?

Central Dogma refers to the flow of genetic information from DNA to RNA, and finally to proteins. Therefore, this protein is known as the Central Dogma in molecular biology. Francis Crick was the first scientist to hypothecate such a concept.

2. When and Why was the Human Genome Project Launched?

The Human Genome Project launched in 1990. Its primary goal was to decipher the complete human DNA sequence. To do this, genetic engineering and other advanced techniques were used.

3. What is the Meaning of Frameshift Mutation?

Any unforeseen gain or loss in one or two base pairs consequently alters the reading frame. This phenomenon is referred to as a frameshift mutation.