Neurospora Genetics: Beadle and Tatum, Gene Expression & Gene Concepts Neurospora genetics played an important role in understanding the relationship between genes, enzymes and metabolic pathways. Neurospora crassa became an important experimental organism in classical genetics. NEET Quick Focus: Beadle and Tatum → One gene–one enzyme hypothesis → One gene–one polypeptide concept → Cistron, Recon and Muton → Split gene → Transposon → Constitutive and non-constitutive genes. 1. Neurospora Genetics George Beadle played a major role in the development of Neurospora genetics . He introduced Neurospora crassa , commonly known as a pink mould, as an experimental organism for genetic studies. Because of its importance as an experimental organism, Neurospora has historically been compared with Drosophila as a model organism for genetic research. Applications of Neurospora in Genetics ...

Translation: Protein Synthesis | NEET Biology Notes Translation is the process of protein synthesis . It involves the formation of a polypeptide chain by polymerisation of amino acids according to the information present in mRNA. In simple terms, translation involves the conversion of the nucleotide sequence or "language" of mRNA into the amino-acid sequence of a protein . 1. Translation Unit A part of mRNA having coded information for a polypeptide is called a translation unit . A translation unit consists of: Initiation codon Coding region Termination codon The initiation codon is generally AUG , which codes for methionine . 2. Components Required for Translation The major components involved in protein synthesis are: mRNA tRNA Ribosomes Amino acids Aminoacyl-tRNA synthetase Energy in the form of ATP and GTP The riboso...

Transcription: Process of RNA Synthesis from DNA | NEET Biology Notes Transcription is the process of synthesis of RNA from DNA. It is an important step of gene expression in which genetic information present in DNA is copied into RNA. 1. Principle of Complementarity Transcription is based on the principle of complementarity . Non-template / Coding / Sense strand: 5′ → 3′ Template / Non-coding / Antisense / Master strand: 3′ → 5′ RNA is synthesized complementary to the template DNA strand. During transcription, only a part of DNA containing information for a particular protein is transcribed. Only one strand of DNA, generally the 3′ → 5′ template strand , acts as the template for RNA synthesis. If both strands of DNA acted as templates, two complementary RNA molecules would be produced. These RNA molecules could pair with each other to form double-stranded RNA, which could interfere with translation. 2. Transcription Unit A part of double-stranded DNA ...

Wobble Hypothesis, Central Dogma of Molecular Biology & Reverse Transcription This article covers important concepts related to genetic code, translation, the wobble hypothesis, central dogma, reverse transcription and RNA-dependent DNA polymerase for NEET and CBSE Biology. Additional Point About Replication and Transcription During DNA replication and transcription , nucleotides are added in the form of nucleoside triphosphates . Nucleoside triphosphates perform a dual function: They act as substrates for nucleic acid synthesis. They provide the energy required for the polymerization reaction. Wobble Hypothesis The wobble hypothesis was proposed by Francis Crick to explain how a relatively small number of tRNA molecules can recognize multiple codons. According to the wobble hypothesis, base pairing between the third base of the mRNA codon and the corresponding base of the tRNA anticodon is less stringent than pairing at the first two positions. Wobble Position The th...

Genetic Code: Features, Codons, Degeneracy and Universal Nature The genetic code is the set of rules by which the nucleotide sequence of mRNA is translated into the amino acid sequence of a protein. The genetic code is commonly represented using mRNA codons . What Is a Codon? A codon is a sequence of three nucleotides in mRNA that specifies an amino acid or a termination signal during protein synthesis. There are 64 possible codons in the genetic code: 61 codons specify amino acids. 3 codons are stop/termination codons. Discovery of the Genetic Code The term genetic code was introduced by George Gamow . Important early experimental work on deciphering the genetic code was carried out by scientists including Marshall Nirenberg and J. Heinrich Matthaei . The first codon to be deciphered was UUU , which codes for phenylalanine . Sense and Nonsense Codons Sense Codon A sense codon specifies an amino acid. Nonsense or Stop Codon A nonsense codon , also called a ter...

RNA: Types, Structure, Functions, mRNA, tRNA and rRNA RNA (Ribonucleic Acid) is an important biological macromolecule involved in genetic information transfer, protein synthesis and gene regulation. In some viruses, RNA also functions as the genetic material. RNA World The term RNA World was coined by Walter Gilbert . The RNA world hypothesis proposes that RNA may have played a central role in early life because it can function both as a carrier of genetic information and as a catalyst. RNA as Genetic Material RNA is considered to be an ancient form of genetic material. At present, RNA acts as genetic material in several viruses, whereas DNA is the primary genetic material in most cellular organisms. RNA can store and transmit genetic information and can also possess catalytic activity. However, RNA is chemically less stable than DNA and is therefore less suitable for long-term storage of genetic information. Why Is RNA Less Stable Than DNA? RNA contains the sugar ribose , which has...

DNA Replication: Types, Semiconservative Replication, Meselson–Stahl Experiment & Mechanism DNA replication is the biological process by which a DNA molecule produces two daughter DNA molecules. It is an essential process for growth, development, cell division, heredity, and transmission of genetic information. What Is DNA Replication? Replication is an autocatalytic function of DNA , in which one molecule of DNA synthesizes two molecules of DNA. DNA replication takes place during the S-phase (Synthesis phase) of the cell cycle . In rapidly growing bacteria such as Escherichia coli , DNA replication can proceed at a very high rate, approximately 2,000 base pairs per second . Types of DNA Replication DNA replication can be described on the basis of several features: Semiconservative replication Semi-discontinuous replication Bidirectional replication Monorepliconic replication Multirepliconic replication 1. Semiconservative Replication In semiconservative DNA repli...